Compactación

Professor Dr.-Ing. Dr.-Ing. E.h. Rudolf Floss

Compaction Technology in Earthwork, Highway and

Transportation EngineeringVolume 1

Basic Principles of Vibratory CompactionCompaction of Soil and Rock

Compaction of Asphalt








Transportation Engineering






Specialist book of BOMAG GmbH & Co. OHG, Germany, 1st edition 2001Published by BOMAG GmbH & Co. OHG

Impressum

© BOMAG GmbH & Co. OHG, Germany, all rights reserved

Publisher:BOMAG GmbH & Co. OHG, Boppard

Project Management:Dipl. Ing. H.-J. Kloubert, BOMAG GmbH & Co. OHG, Boppard

Prof. Dr.-Ing. Dr.-Ing. E. h. Rudolf Floss, Munich

Layout:Schray – Grafisches Atelier, Weissach

Translation:Techtrans GmbH, Boppard

Print:Druckerei Seyl & Hohn, Koblenz

Publisher‘s notes:The publication in its entirity is protected by copyright. All details, data, results etc. contained in this book have been

reviewed by the project management according to the best of knowledge under utmost care. At the same time, errors

Preface

Mechanical compaction technology with vibratory compaction equipment has reached a high level of development. It has matured to an economical and technically indispensable construction techno-logy used all over the world for the construction of permanently stable and deformation resistant high-ways, transportation routes, earth work, embank-ments and foundations of buildings, bridges, sealing layers and waste disposal sites.

These engineering projects are characterised by increasing output, a strong weighting of economi-cal aspects and high quality demands. Compaction equipment must be powerful, economical and ver-satile in use and contribute to a surface covering quality assurance by means of an immediate work integrated control.

BOMAG has recognised these trends and deve-lopment objectives and already in the eighties tho-roughly investigated compaction processes when using vibratory rollers and the interaction between drum vibration and the soil reaction force changing with increasing compaction.

The push in innovation resulting from this led to the development of automatic measuring and recording systems. With these roller integrated systems the compaction processes can be controlled and opti-mised and provide a surface covering recording of the compaction.

In recent years further research and development activities led to the successful launch of intelligent BOMAG compaction systems such as VARIOMATIC and VARIOCONTROL, which automatically adapt the compaction amplitude to the actual operating conditions. These controlled rollers particularly stand out in terms of compaction performance, depth effect, uniform compaction and suitability for universal use.

Last but not least, the demand for more powerful padfoot rollers for fine grain and rockfill materials, as used on large scale civil engineering projects of the German Railway, led to the development of new padfoot designs.

Systematic fundamental investigations in the Research and Development Centre of BOMAG as well as application oriented investigations on large scale construction sites were the essential prere-quisites for this progress. The author of this first edition of the BOMAG specialist book, University Professor Dr. Ing. Dr. Ing. e.h. Rudolf Floss, has scientifically contributed on these researches and developments over many years.

Purpose and goal of this specialist book is the presentation of the know-how about BOMAG com-paction technology in connection with the scientific state of fundamental knowledge in a comprehen-sive publication. Volume 1 available in German and English and the planned successive volume shall be available for all those who are interested in BOMAG equipment. The experience contained ther-ein shall help civil engineering contractors, autho-rities, and consulting engineers in the planning and execution of compaction tasks in earthwork, Transportation routes and landfill site construction, but shall also provide fundamental knowledge for experts in research and science.

Boppard, March 2001 BOMAG Management

Introduction

Research and development in the field of compac-tion technology concentrates on enhancing the per-formance capacity of machines, on user friendly and environmentally compatible designs and on extending the functional structural range of applica-tion. These improvements, which are achieved in a continuous process, occur temporally parallel with the development of electronic measuring and com-puting technology as well as the use of micro-proc-essor controls.

An important radical change and milestone in this respect is the introduction of automatic measuring and recording systems as well as EDP and GPS based machine controls. These machine integrated systems enable an almost automatic control of compaction work and an optimisation of the use of equipment as well as a surface covering assur-ance of the compaction quality. The application of the construction machine as a “measuring and test-ing unit” and the use of the machine parameters for process control is essential for large area projects, because it is the only way to achieve a uniform placement quality and the reliability of the quality assurance in accordance with the required con-struction progress.

A development leap in control automation of vibra-tory rollers has been in fact achieved by the pos-sibility to combine data of compaction quality and compaction management with DGPS-information (Differential Global Position Systems) about the position of the roller. Further developments aim at the possibility to localise the roller position exactly via a position system suitable for practical applica-tions and to specify, control and record the number of roller passes. The further development of the machine integrated measuring and recording sys-tems as well as the localisation of the roller by means of satellite navigation will also enable the linkage of the position data with the compaction data and the real time presentation in a 3 D-model. Furthermore, poking interfaces for DGM planning software (digital terrain models) are planned, so that the actual position can be compared with the nominal data during the compaction process in a work integrated manner.

The great present and future challenges of engi-neering technology induce BOMAG and the author of this specialist book to communicate, in form of a compendium, the state-of-the-art concerning the optimisation and automation of equipment engi-neering and compaction technology gained by research and investigating to the public and espe-cially to those persons interested in BOMAG com-paction technology.

Volume one of this specialist book is divided into three parts. The first part contains the fundamental principles of vibratory compaction, the characteris-tic equipment technological parameters as well as the design types of and applications for BOMAG vibratory compactors.

The second part deals with the compaction of soil and rock in connection with the operative range of the BOMAG compaction technology in earthwork and embankment construction, describing the soil and rock mechanical principles of compaction and subsequently the recommendations for vibratory equipment with performance data.

The third part contains, in a similar way, experiences and equipment recommendations for the compac-tion of asphalt pavements as applied in highway and transportation engineering and for sealing layers.

The appendix contains several conversion tables and reference lists as general assistance for the user of this book.

For the intended sequential volume special sub-jects and special applications for the BOMAG com-paction technology are planned. This includes sub-jects such as the compaction of unbonded and hydraulically bonded base courses and soil-binder mixes in highway and transportation engineering, the compaction of recycling materials, industrial wastes and household refuse, the compaction of cable and pipeline trenches, construction backfills and embankments, as well as the compaction of sanitary landfill constructions and mineral sealing layers. Furthermore, special chapters will deal with fundamental principles and information for the cal-culation of output and costs of compaction work, as well as measuring, testing and recording systems for quality assurance of compaction work.

The author would like to thank BOMAG for the pub-lication of this specialist book, namely Mr. Dipl.-Ing. Hans-Josef Kloubert, who has made a signifi-cant contribution with their engineering knowledge and editorial support. The author would also like to thank BOMAG executives in the research and engi-neering department for the useful discussions.

BOMAG and author wish all users of this specialist book many inspirations and beneficial information for their daily work.

Munich, March 2001Univ. Prof. Dr.-Ing. Dr.-Ing. E.h.Rudolf Floss

2

1

Table of Contents

Part 1 Fundamental principles of vibratory compaction

1 Principles of dynamic vibration

1.1 Basic vibrations ............................................................................................................................. 71.2 Natural and resonance vibrations .................................................................................................. 81.3 Harmonic and subharmonic vibrations .......................................................................................... 91.4 Propagation of vibrations ............................................................................................................... 91.5 Dynamic forces and resilient stiffness of the subsoil ................................................................... 10

2 Vibration and movement performance of the system types

2.1 Vibration exciter systems for vibratory rollers .............................................................................. 112.1.1 Vibrator (circular vibrator) ............................................................................................................ 112.1.2 Oscillator ...................................................................................................................................... 112.1.3 Comparative compaction effect of vibrator and oscillator ............................................................ 122.1.4 BOMAG directed vibration systems ............................................................................................. 132.2 Parameters of vibration generation .............................................................................................. 172.3 Static axle load and vibrating mass ............................................................................................. 172.4 Centrifugal force, frequency, amplitude........................................................................................ 172.5 Energy transfer............................................................................................................................. 20

3 Design types and applications for BOMAG compaction technology

3.1 Vibratory tampers......................................................................................................................... 233.2 Vibratory plates / hydraulic plates ................................................................................................ 233.3 Hand guided vibratory rollers ....................................................................................................... 253.4 Tandem rollers ............................................................................................................................. 263.5 Single drum rollers with smooth drum.......................................................................................... 283.6 Single drum rollers with padfoot drum ......................................................................................... 303.7 Towed vibratory rollers ................................................................................................................. 32

2

Table of Contents

Part 2 Compaction of soil and rock in earthwork

1 Soil

1.1 Soil groups under engineering aspects........................................................................................ 33 1.2 Earth engineering classification ................................................................................................... 381.3 Geotechnical suitability of the soil types ...................................................................................... 401.3.1 Material and engineering properties ............................................................................................ 401.3.2 Geotechnical suitability for earthwork .......................................................................................... 431.3.2.1 Clays and silts ............................................................................................................................. 431.3.2.2 Sands and gravel......................................................................................................................... 441.3.2.3 Mixed particle soils ...................................................................................................................... 451.4 Compaction characteristics of the soils........................................................................................ 461.4.1 Compaction parameters............................................................................................................... 461.4.2 Compaction characteristics.......................................................................................................... 481.4.2.1 Functional interrelationship.......................................................................................................... 481.4.2.2 Coarse particle soils .................................................................................................................... 491.4.2.3 Fine particle soils......................................................................................................................... 501.4.2.4 Mixed particle soils ...................................................................................................................... 511.4.3 Relations between compaction and deformation parameters ...................................................... 511.4.3.1 Test dependent deformation parameters ..................................................................................... 511.4.3.2 Soil specific interrelationships ..................................................................................................... 541.4.3.3 Relationships to international soil classifications......................................................................... 56

2 Rock

2.1 Classification of rock (overview)................................................................................................... 572.1.1 Congealed rock (magmatic rock) ................................................................................................. 572.1.2 Sedimentary rock ......................................................................................................................... 572.1.3 Metamorphic rock ........................................................................................................................ 572.2 Description of rock ....................................................................................................................... 582.3 Parting plane structure of rock ..................................................................................................... 582.4 Strength and deformation properties of rocks.............................................................................. 592.5 Suitability of rock.......................................................................................................................... 602.5.1 Exploitation of rock as filling material ........................................................................................... 602.5.2 Rock classes................................................................................................................................ 602.5.3 Placement and compaction.......................................................................................................... 61

3

3 Application and performance of the BOMAG compaction technology

3.1 Applications.................................................................................................................................. 643.2 Calculation of compaction output................................................................................................. 663.3 Trial compaction ........................................................................................................................... 683.4 Placement and compaction water content ................................................................................... 703.5 General equipment and soil specific recommendations .............................................................. 723.6 Special machine specific compaction effects............................................................................... 753.6.1 Static smooth drum rollers ........................................................................................................... 753.6.2 Pneumatic tired roller ................................................................................................................... 763.6.3 Smooth drum vibratory roller ....................................................................................................... 763.6.4 Padfoot rollers with and without vibration..................................................................................... 763.6.5 Single drum rollers with special padfoot drums ........................................................................... 773.7 Compaction of marginal zones (slopes, embankment shoulder) ................................................. 783.8 Compaction of layers on elastic base .......................................................................................... 79

4

Table of Contents

Part 3 Compaction of asphalt

1 Asphalt pavements in highway and transportation engineering ........................................ 81 2 Bitumen and bituminous binders

2.1 Types and manufacturing ............................................................................................................. 832.2 Chemical-physical properties....................................................................................................... 842.3 Tests............................................................................................................................................. 852.4 Material specific requirements ..................................................................................................... 872.4.1 Paving bitumen ............................................................................................................................ 872.4.2 Special bitumens and bituminous binders ................................................................................... 88

3 Asphalt

3.1 Mineral aggregates ...................................................................................................................... 893.2 Asphalt for base courses.............................................................................................................. 913.3 Asphalt for surfacing .................................................................................................................... 923.3.1 General requirements .................................................................................................................. 923.3.2 Binder coarse asphalt .................................................................................................................. 943.3.3 Asphalt concrete .......................................................................................................................... 953.3.4 Stone mastic asphalt.................................................................................................................... 963.3.5 Gussasphalt ................................................................................................................................. 973.3.6 Asphalt mastic.............................................................................................................................. 983.3.7 Combined surface - base - courses ............................................................................................. 983.3.8 Natural asphalt and modified asphalt........................................................................................... 983.3.9 Asphalts for special construction methods................................................................................... 983.4 Asphalt veneer coats ................................................................................................................... 99

4 Compaction characteristics of asphalt

4.1 Fundamentals ............................................................................................................................ 1004.2 Tests methods............................................................................................................................ 1014.2.1 Marshall stability and flow .......................................................................................................... 1014.2.2 Compactibility............................................................................................................................. 1024.3 Influencing factors ...................................................................................................................... 1034.3.1 Composition of mixture .............................................................................................................. 1034.3.2 Influence of the temperature ...................................................................................................... 104

5

5 Application and performance of BOMAG compaction technology in asphalt engineering

5.1 Planning and fields of application.............................................................................................. 1055.2 Influences caused by ambient laying and compaction conditions............................................. 1075.3 Areal output and volumetric output of the machines ................................................................. 1095.4 Compaction equipment ............................................................................................................. 1135.4.1 Pre-compaction during pavin .................................................................................................... 1135.4.2 Selection criteria ....................................................................................................................... 1135.4.3 Static smooth drum rollers ........................................................................................................ 1145.4.4 Pneumatic-tired rollers .............................................................................................................. 115 5.4.5 Vibratory rollers......................................................................................................................... 1165.4.5.1 Effectiveness in asphalt compaction ......................................................................................... 1165.4.5.2 Hand guided vibratory rollers .................................................................................................... 1165.4.5.3 Tandem vibratory rollers............................................................................................................ 1175.4.5.4 Combination rollers ................................................................................................................... 1185.4.5.5 Plates and tampers ................................................................................................................... 1195.4.6 Applicational advantages of the directed vibration system BOMAG VARIOMATIC................... 1195.4.7 List of recommendations for the use of BOMAG vibratory rollers ............................................. 1205.5 Basic rules for rolling technique ................................................................................................ 1225.5.1 Rolling pattern........................................................................................................................... 1225.5.2 Monitoring of quality influences................................................................................................. 125

Appendices

A 1 Conversion tables............................................................................................................................ 129A 2 Compaction parameters (soil) ......................................................................................................... 131A 2 Conversion of compaction parameters............................................................................................ 133A 3 Characteristics of rock..................................................................................................................... 134A 4 Standards, regulations, guidelines .................................................................................................. 135

Literature ............................................................................................................................................. 141

Glossary ............................................................................................................................................. 147

6

7

1 Principles of dynamic vibration

1.1 Basic vibrations

With their rotating eccentric masses (unbalanced masses) mounted on one or several drive shafts, depending on the system, the vibratory machines designed for vibratory compaction generate uni-form, stable rotary vibrations. These vibrations are transferred to the substrate via contact areas (spe-cial padfeet, plates, roller drum), either flat or linear. They act as dynamic forces in a spatially distributed manner, compact the medium by means of pres-sure and vibration and, with these volume reduc-ing deformations, increase the physical-mechanical stiffness characteristics.

The interaction between vibration exciter and medium to be compacted - e.g. a soil layer - can be schematically presented using a dynamic substitu-tion model.

The basic vibrations of the exciter system normally have harmonic, periodic attributes, (fundamentals Lit. 1, 2, 5, 6):

The temporal change of harmonic vibrations is defined and described by sine or cosine functions (Fig. 2).

The vibration is periodic if it is continuously repeated after a certain period of time. A periodic vibration can be graphically presented as a super-imposition of several sine or cosine oscillations, the frequency of which is a multiple of the basic fre-quency.

A stationary vibration is a vibration with tempo-rally constant characteristic functions. Temporary vibration processes (transient and dying processes) are transient vibrations, which will either dissi-pate in the course of time or change over to a sta-tionary condition.

Deterministic vibrations are vibrations that do not occur by chance; their momentary vibration magni-tude can be mathematically exactly described on the basis of the previous course of time. In con-trast to this, random or stochastic vibration pro-cesses showing irregular variations of time, can only be described with the help of statistic or proba-bilistic parameters.

Fig. 2 shows a sinusoidal oscillation process as time function of the vibration displacement a‘ = f(t). The sequence of movement of this vibration type is generally characterised by the following definition and mathematical derivations:

f Frequency, reciprocal value of the vibration period T (duration of period) f = 1 [Hz = s-1]

ω Radian frequency, number of vibrations in 2 π seconds ω = 2 π . f = 2π

a Amplitude [mm]

a‘ Vibration displacement: a‘ = a . sin (2 π . f . t)

Compactor

Soil

M suspendet machine massm1 exciter massm2 resonant vibrating soil massr1 machine dampingr2 soil dampingk1 resilience value of machinek2 resilience value of soilFo exciter force

T

T

Fundamental principles of vibratory compactionPart 1

Compactor - soil - substitution model Fig. 1

T

8

the natural frequency f multiplied by 2 π is called natural radian frequency ω0.If a vibration system possesses several natural fre-quencies (e.g. compaction machine and dynam-ically coupled soil mass), each of these natural frequencies also has its own type of vibration. When exciting such a system with a frequency which is more or less identical with one of the natural fre-quencies, resonance frequencies with high ampli-tudes will occur.

According to the resonance theory (Hertwig 1933, Lit. 1) the optimal compaction effect is obtained in the range of the natural frequency of the system machine - substrate (resonance frequency). Under this condition the substrate responds elastically, similar to a spring, whereby the natural radian fre-quency ω0

2 depends in a linear relation on the spring stiffness C and the total vibrating mass m of the system:

ω02 = c . m

Depending on substrate and machine parameters, the natural frequencies are located in the range between 13 and 27 Hz (800 - 1.600 vibrations/minute). Investigations reveal that the natural fre-quency of the system drops with increasing nomi-nal amplitude (Lit. 3).

T

Vibration path a‘

Amplitude a

Time t

T

Fig. 2Sinosoidal vibration process:Path-time-diagram

Vibration speed v and vibration acceleration b are temporal derivations from the vibration displace-ments a‘:

Vibration speed: v = da‘ = a (2 π . f) . cos (2 π . f . t) v = v sin (2 π . f . t + π )) v = a . 2 π . f

Vibration acceleration: b = dv = a (2 π . f)2 . sin (2 π . f . t) b = b . sin (2 π . f . t + π) b = v . 2 π . f = a (2 π . f)2

Parameters of vibration generation for the system types, Fig. 16.

1.2 Natural and resonance vibrations

Natural vibrations characterise system inherent vibrations, which solely depend on the properties of the system (e.g. the properties of the compaction machine: dimensions, material parameters, contact as well as marginal conditions) and adjust them-selves after a short excitation period independently from the excitation magnitude.As far as these natural vibrations are characterised by harmonic vibration features, basic terms as in part 1, section 1.1 are used: Each vibration mag-nitude reappears after the system inherent period duration T (duration of natural vibration). The recip-rocal value of the system inherent period duration T0 is the natural frequency f0 = 1/T0. The value of

dt

2

dt

Part 1

Fig. 3Change of frequency in connection with amplitude eccentric mass (Machet 1976)

9

Fundamental principles of vibratory compaction

1.3 Harmonic and subharmonic vibrations

Vibration exciters and oscillating masses of the sub-strate to be compacted form a coupled vibration system. During the compaction process the basic vibration of the machine’s exciter system is changed or disturbed by the stiffness of the dynamically cou-pled mass. These changes in the periodic sequence of movement result in harmonic vibrations, which are a multiple of the basic vibration generated by the exciter. The magnitude of these harmonic vibrations increases with progressing compaction or with the stiffness of the substrate and is therefore an indirect measure for the dynamic change in stiffness. This process reaches a limit condition when the machine lifts off the substrate or “jumps” at a very high stiff-ness. In this jump condition so-called subharmonic vibrations, half the size of the basic vibration, occur besides the basic vibrations generated by the exciter.For example, on vibratory rollers used in earthwork with a normal vibration frequency of approx. 30 Hz, the harmonic vibrations reach 60 Hz and the subhar-monic vibrations 15 Hz.

1.4 Propagation of vibrations

In the dynamically coupled strata the introduced vibra-tion energy spreads in form of space waves (com-pression and shearing waves) and surface waves or even as a combination of both wave types (Fig. 4). The magnitude of these wave types depends on the type of vibration exciter and the introduction of the energy. Since the source of excitation for the vibratory compaction of layers described hereunder is located near the surface, the vibrations mainly spread in form of surface waves. Depending on the distance from the source of excitation, these surface waves have higher vibration amplitudes than the space waves.

The transferred vibrations dissipate with increasing distance from the source of excitation. This is caused by the geometric decrease of the amplitudes as a result of the reduction in energy density and by the material damping caused by the frequency depend-ent absorption of vibration energy. Vibrations with higher frequencies are thereby dampened more than vibrations with low frequencies (Lit. 9).

Locally the propagation of vibrations may be consid-erably disturbed or obstructed, e.g. by extreme divi-sion of layers, building density, clefts in the terrain and the interaction of several vibration sources. In case of distinct layer borders with high density differ-ences, existence of groundwater or loads not applied to the ground the propagation of vibration concen-trates along the surface.

Compared with vibrations originating from blasting activities the propagation of waves from vibration exci-tation introduced by vibratory equipment on the sur-face is only of minor significance. However, during the compaction process the fact must be taken into con-sideration that both surface waves as well as space waves have an effect on buildings (pipes, wall and shaft constructions); example Fig. 5.

Fig. 4Wave propagation of the vibration energy

10

1.5 Dynamic forces and resilient stiffness of the subsoil

Forces, which are variable with respect to their effective duration and direction, are known as dynamic forces. If the effective duration of the force is short in relation to the periodic duration of the natural vibration of the system, the force acts as a blow and depends on the size of the impulse.

Vibration magnitudes (speed, acceleration, ampli-tude) are measured as function of time by acceler-ation measurements on the compaction machine. From the measured accelerations a force-way-func-tion can be derived by mathematical evaluation of the soil contact force and the integration of the accelerations and presented as a so-called indica-tor diagram. The released energy or power is an

indirect measure for the dynamic stiffness of the subsoil. The increase of the contact force in rela-tion to the respective assigned vibration displace-ment corresponds with the momentarily achieved dynamic stiffness of the subsoil achieved by com-paction; see T 1, para. 2.5 and Fig. 21.

Vibration speed at a foundation[mm/sec]

4

3

2

1

5

200kg-700kg 2t 6t 9t 17t 18t 19t Vibratory plates Tandem-vibratory rollers Single drum rollers Compaction equipment

10m distance 5 m distance 2 m distance

Fig. 5Effects of vibrations generated by vibratory compaction equipment on a hall building

Part 1

11

2 Vibration and movement performance of the system types

Overview of the system types (matrix) as in Fig. 6

2.1 Vibration exciter systems for vibratory rollers

The vibration and movement performance of vibra-tory rollers change with increasing stiffness of the soil layers which develops in the course of com-paction. This interaction between the reactive per-formance of the roller and the stiffness of the soil depends on soil specific and machine character-istic influence magnitudes. When weighting these influencing parameters a distinction must be made as to their effect on the compaction process. T 1, para. 2 describes the substantial vibration and equipment parameters which interact in an accu-mulated way, depending on the type of machine.

Vibratory rollers work with various types of vibration exciters which, depending on design and system produce non-directed or directed rotational vibra-tions by eccentric masses.

2.1.1 Vibrator (circular vibrator)

The exciter system consists of a central drive and exciter shaft with an attached unbalanced mass. The fast rotation of the exciter shaft generates cen-trifugal forces rotating 360° with undirected rota-tion vibrations. This type of vibration exciter is also known under the name single shaft rotation vibrator (Fig. 7).

2.1.2 Oscillator

The exciter system consists of a central drive shaft and two rotating exciter shafts with the same sense of rotation. The unbalanced masses of these toothed belt driven exciter shafts are 180° offset to each other, thereby generating a varying moment around the central axis. This exciter system gen-erates an oscillating, i.e. rotary movement of the drum, whereby the drum is permanently in contact with the soil, without any blows and impact (Fig. 8).

Circular vibrator Directed vibrator

Circular vibrator Oscillator

Directed vibrator(Variomatic 1)

Directed vibrator(Variocontrol)

Fig. 6Vibration exciter systems

Fig. 7Circular vibrator


12

With the oscillation principle, which has previously only been developed for and used in special com-pactors, it is assumed that the oscillatory move-ment of the drum together with the support of the effective axle load introduces a compaction effec-tive shear stress to the surface of the substrate.

2.1.3 Comparative compaction effect of vibrator and oscillator

Figures 9 and 10 show the results of measurements obtained from pressure and acceleration transduc-ers to compare the different performances of vibra-tor and oscillator with respect to vertical pressures as well as vertical and horizontal accelerations.

Figure 9 clearly shows that the maximum vertical pressures achieved by the vibrator are several times higher than with the oscillator and that the oscillator works statically without losing ground contact. The comparison in Fig. 10 reveals that, due to its princi-ple, the oscillator can only introduce minor vertical accelerations compared with the vibrator. From Fig. 10 the conclusion can be made, that the horizontal accelerations of the oscillator are also of minor sig-nificance in comparison with the vibrator.

Fig. 8Oscillator system

Toot

h be

lt

Fig. 9Vibrator, vertical pressure distribution

Oscillator, vertical pressure distribution

Part 1

13

Fig. 10Vibrator, horizontal acceleration

Vibrator, vertical acceleration

Oscillator, vertical acceleration

Oscillator, horizontal acceleration

The differences shown in the illustrations, which quantitatively only apply for the examined silty gravel, but qualitatively reveal the different compac-tion effects of both systems, can be explained by the fact that the vibrator has the effect of a combi-nation of directed vibrator and oscillator. Since the vibrator applies a higher pressure force the vibrator not only introduces a higher vertical compression, but also a higher shear stress than the oscillator.

2.1.4 BOMAG directed vibration systems

The directed vibration systems from BOMAG unify the advantages of rotary and oscillatory vibrators. With the newly developed directed vibration sys-tems VARIO for vibratory rollers a long striven goal of development and an important technological leap was achieved. These new self-controlling systems automatically detect and adjust the energy required for compaction. These systems are based on the analysis of the interaction between the drum and the stiffness of the material to be compacted. The compaction energy is automatically optimised by using the acceleration signals. This adaptation has the effect that the maximum possible compaction energy is transferred at any time, without the drum changing over to a unfavourable jump operation or causing any overcompaction.

For the compaction of asphalt a directed vibrator, the VARIOMATIC system (Fig. 11), was developed. This system consists of two counter-rotating eccen-tric shafts and generates directed vibrations. The direction of the resulting force can be automatically changed between vertical and horizontal (oscilla-tion), depending on the stiffness of the substrate, by simply offsetting one shaft in relation to the other. Both shafts are synchronised by a pair of gears. The control of the force direction is accommodated by a control circuit. The adjustment of the eccen-trics is accomplished by a hydraulically controlled adjustment cylinder with integrated way measuring system.


14

Two acceleration transducers pick up the stiffness data of the substrate and transmit these to a pro-grammable logic control (PLC), which then sends signals to the control unit. The exchange of signals is accomplished by a new, high-speed valve tech-nology.

The vertical component of the amplitude (effective amplitude), which is of major importance for the compaction, is automatically reduced before the machine changes to jump operation because of a too high stiffness of the soil or a too high effec-tive amplitude. This not only optimises the energy requirement, but also leads to a material preserving and uniform compaction.

Besides the automatic mode, in which the system controls itself, it is also possible to pre-select a cer-tain direction of vibration. In this case he can select from a choice of 6 vibrating directions between hori-zontal and vertical (Fig. 12).

The higher amplitudes needed for the large vibra-tory rollers used in earthwork led to the develop-ment of the VARIOCONTROL system (Fig. 13). This new exciter system with its vibrating mass of 9000 kg

generates vibration amplitudes of up to 2.5 mm and centrifugal forces of up to 500 kN. Two concen-trically arranged vibrator shafts carry three eccen-tric weights, the two smaller weights near the ends and the large eccentric weight in the middle of the exciter shaft (Fig. 14). The middle eccentric weight rotates in the opposite direction of the outer weights. The resulting centrifugal forces add up to a directed vibration. The effective direction of this directed vibration can be adjusted by turning the complete vibrator unit. Any desired angle position between horizontal and vertical direction of vibra-tion is possible. The control technology is based on the same concept as for the VARIOMATIC system.

With increasing compaction the directed vibrator changes automatically from the vertical direction of vibration with high vertical acceleration towards the horizontal direction of vibration with a reduced effective amplitude. The amplitude is continually adapted so that areas with low stiffness are com-pacted with a high effective amplitude and areas with an already high stiffness with an appropriately lower effective amplitude. The offered compaction energy is thereby automatically reduced when the stiffness of the soil becomes too high. This method ensures that high amplitude generated by the vibra-tion system achieves a favourable depth effect already during the first passes and that a premature lid or plate effect can be avoided.

Fig. 11

VARIOMATIC 2 Vibratory roller with self-regulating direction of force and effective amplitude

Fig. 12VARIOMATIC Control unit

Part 1

15

250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5

Bodenkontaktkraft [kN]

250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5

Bodenkontaktkraft [kN]250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


250200150100500

[mm]-4 -3 -2 -1 0 1 2 3 4 5


130

120

110

100

90

80

70

60

50

40

30

20

10

05 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 [m]

6th pass

3th pass

1th pass

EV

IB [

MN

/m2 ]

Fig. 15

Dynamic stiffness EVIB determined with the VARIOCONTROL system on silty gravel

Fig. 14VARIOCONTROL, design of exciter system

Fig. 13

VARIOCONTROL single drum roller with automatic or selectable amplitude and stiffness control

FB

FZ

m . aAcceleration measurementand recording of values

Rolling track

Processor

FB

S

EVIB

FB = Ground contact forces = Vibration path


16

The angular position of the directed vibrator of the

Axle load, drum (Fstat) = static weight of drum and [kg] drum frame

Axle load, drum (kg) Static linear load = [kg/cm] Drum width (cm)

Vibrating mass (M0) = Drum mass under vibratory motion [kg]

Number of revolutions of eccentric Frequency (f) = , f = 1/T . n [Hz] Unit of time Angular velocity (ω) = 2πf [1/sec]

Unbalanced mass (me) = eccentric mass [kg] Eccentricity (e) = distance between gravity centre of eccentric and rotation axis [mm]

Eccentric moment (Me) = eccentric mass, Me = me . e [kg . mm]

Centrifugal force (FC) = Fc = me. e ω2 = me

. e (2πf)2 [N] Unbalanced moment(Me) Theoretical amplitude (a) = [mm] Vibrating mass (M0)

Total weightstatic linear load vibrating

massamplitude frequency

Amplitude

Vibration pathTime for revolution of eccentric

Mov

emen

t

Vibrating mass

Eccentric massCentre of gravity ofeccentric mass

Eccentricity

Fig. 16Parameters of vibration generation

Part 1

17

VARIOCONTROL system can be used for a direct and surface covering determination of the dynamic stiffness of the soil (T 1, para. 2.5 and Fig. 15). For this purpose the ground contact force is determined on the basis of the accelerations measured on the vibrating part of the drum and a force-path-diagram is developed by integration of the acceleration. The ratio of the contact force to the related path of com-pression corresponds with the dynamic stiffness of the soil. The dynamic stiffness provides a physical magnitude as a measure for the compaction status. It can be directly measured and, in comparison with the previously used non-dimensional magnitudes, it is considerably less influenced by machine related parameters (amplitude, frequency, travel speed).

2.2 Parameters of vibration generation

On vibratory rollers the generation of vibrations is characterised by the machine related parameters listed in Fig. 16. In T 1, para. 1 these fundamental values are described in more detail (Lit 7, 8, 10).

2.3 Static axle load and vibrating mass

The statically effective mass consists of the drum axle load (kg). The static linear load is mathemati-cally determined by the static axle load Fstat, divided by the drum width (kg/cm). The drum diameter influ-ences the static linear load in as far as a high drum axle load requires an appropriately large diameter. When increasing the static axle load while leaving other influential parameters unchanged, the static and dynamic pressure strain applied to the soil by

the drum increase almost proportionally with the axle load. The penetration depth of this stress or the effective compaction depth increases accordingly.

The vibrating mass M0 contains all vibrating parts of the machine, such as drum, hydraulics, mass of eccentric and others. The ratio of this vibrating mass to the mass of the suspended and statically effec-tive drum frame influences any compaction effect or the compaction depth. The compaction effect rises with increasing vibrating mass, while other parameters remain comparably constant, because the vibrating mass is dynamically coupled to the sympathetic mass of the soil layers (Lorenz 1934, Lit. 2). The vibrating mass changes with the vibra-tion amplitude generated by the centrifugal force. The increasing vibration amplitude mobilises also less sympathetic mass particles in the soil layers so that the natural frequency of the vibration system drops.

2.4 Centrifugal force, frequency, amplitude

Centrifugal force, frequency and amplitude are fun-damental machine related magnitudes which con-trol the energy transfer during compaction. However, depending on the type and stiffness of the soil their individual influence has different effects and they must therefore be weighted in a differentiated manner.

The centrifugal force FC is generated by the eccen-tric mass me rotating with a rotary or angular veloc-ity e (revolutions per minute). The gravity centre of the eccentric mass is centred at a distance e from the centre of the rotation axis.

Abb. 17Position of eccentric in connection with the vibration path of the drum

Verticalamplitude


18

v

The diagram in Fig. 18, Lit. 3, confirms that the influ-ence of the frequency is limited and that there is no interrelationship between the mathematical vibra-tion force and the centrifugal force. Strong irregular impacts, as occurring during jump operation of the drum, may cause overcompaction or result in a decrease of density. During such jumping of the drum excessive vibrations are generated in the drum frame and the rubber damping elements between drum and fame are highly stressed.

The variations in frequency only have a limited effect on the vibration force. The energy transferred into the base rises with a comparably constant vibration force and an increasing frequency. For this case the compaction energy VE per volumetric unit can be calculated by approximation (Yoo and Selig, 1980, Lit. 4).

VE = f1 (FIstat) + f2 (

a . f)

f1, f2 = values of function, FI

stat = static linear load (kg/cm),a = amplitudef = frequencyv = rolling speed

The centrifugal force increases quadratic with the angular velocity or the frequency f. The rotation velocity of the eccentric determines the number of revolutions n or the frequency of vibrations f = 1/T . n (frequency in Hz or vibrations per unit of time; see T 1, para. 1.1). The nominal vibration amplitude a (mm) depends on the magnitude of the eccentric moment Me (kg . mm)

The drum moves while the eccentric mass is rotat-ing. This movement is 180° out of phase (Fig. 17).

The magnitude of the vibration force effecting the substrate is the result of a complicated interaction between drum and substrate. On the one hand, the centrifugal force is a fundamental unit for the calcu-lation of the vibration force, but on the other hand there is no interrelationship between the two mag-nitudes.

The effective vibration force is mainly activated by the vibration amplitude which, however, is not determined by the centrifugal force. However, the centrifugal force controls the vibration intensity (acceleration) of the drum. The centrifugal force can only be used for a direct comparison between var-ious types of rollers if both static mass and fre-quency are identical, because in this case they reveal the relative differences in amplitudes.

Fig. 18Interrelation between vibration force and frequency (calculation example by Machet 1976)

Ko=5.107 M0=1600C0=2.105 M1- M0=3400K1=5.106 M2=1000C1=9.103 me=1.0

M1-M0

M0

M2

K0

K1

C0

C1

M0 = vibrating mass of machine (exciter mass)M1 = machine massM1-M0 = suspended machine massM2 = resonant vibrating soil mass

Me = unbalanced momentK1 = resilient value of machineK0 = resilient value of soilC1 = damping of machineC0 = damping of soil

Part 1

19

Raising the vibration force up into the range of res-onant frequency has not gained practical signifi-cance, since the vibration level of the entire single drum roller increases extremely in such a case, placing extreme stress on roller and operator. Oper-ation with frequencies in a relatively stable fre-quency range slightly above the resonant frequency is generally of advantage for soil and rockfill com-paction, whereby the resonance effect is also uti-lised to a certain extent.

Fig. 19Influence of the frequency on the compaction amplitude

The optimal effect of vibratory rollers is normally achieved in the frequency range between 25 and 50 Hz (1.500 - 3.000 vibrations per minute). Through-out this entire frequency range both compaction and depth effect are not achieved to such a great extent by the frequency, but mainly by the size of the amplitude and the axle load of the drum (Fig. 19). This influence is apparent with all types of material, however, in dependence on their compo-sition very coarse particle or stony materials as well as cohesive-plastic materials require a high roller mass for an efficient compaction, as far as this is permitted by the shearing strength of these materials. High amplitudes transfer more compac-tion energy deep into the layer to be compacted, but achieve only a minor compaction effect in the upper zone of the layer. Low amplitudes produce only a slight compaction deep inside the layer, but transfer more compaction energy into the zone near the surface.The material specific properties of the substrate thereby cause different reactions to the compac-

tion energy introduced by the vibratory roller. From practical experience the following exemplary values can be used:

• Compaction of soil layers with a relatively high lift height or a large soil volume as well as stony mate-rial: optimal amplitudes ranging from 1.5 to 2.0 mm and optimal frequencies ranging from 25 to 30 Hz (1.500 - 1.800 vibrations / minute). Compare with inherent natural frequencies of soil types acc. to table 1 (Lit. 1, 2).

Soil type Natural frequency Hz Upm

Fine sand ~24 * ~ 1440Non-uniform sand ~27 * ~ 1620Medium sand, uniform ~24 * ~ 1440Medium sand, uniform ~33 ** ~ 1980Sand, moist ~24 ** ~ 1440Sand, dry ~22 ** ~ 1320Sand/gravel ~24-29 ** ~ 1440-1740Loam, solid ~25-29 ** ~ 1500-1740Loam, lose ~21-23 ** ~ 1260-1380Clay, moist ~22 * ~ 1320Clay, dry ~28 * ~ 1620Lime, banked ~30 * ~ 1800Mottled sandstone ~34 * ~ 2040

*H. Lorenz / **F. Fischer

Tabelle 1: Charakteristische Werte für bodenspezifi-sche Eigenfrequenzen (Lorenz, Fischer)

• Compaction of unbonded base courses: favour-ably in the above mentioned frequency and ampli-tude range, because of the high required degree of compaction.

• Compaction of asphalt layers as well as bonded and stabilised base courses, optimal amplitudes ranging from 0.2 - 0.9 mm and favourable frequen-cies ranging from 35 - 60 Hz (2.100 - 3.600 vibra-tions / minute).


20

The rolling speed of the vibratory roller, the increase of which results in a higher area output, has a sig-nificant influence on the compaction effect.

The number of vibration impacts decreases with increasing rolling speed, so that more passes are required to achieve the same compaction effect. Within the normal rolling speed range and with a constant lift height the transferred energy is almost proportional to the ratio between the number of passes and the rolling speed.

When doubling the rolling speed, the number of roller passes should also be approximately dou-bled accordingly. Generally recommended rolling speeds are 1 to 2.5 km/h on rockfill material and clayey soils and 2 to 4 km/h on non-cohesive soils. For asphalt compaction rolling speeds of 2 to 4 km/h have proved most favourable for thick layers or stiff mixtures and 2 to 6 km/h for thin layers or soft mixtures.

2.5 Energy transfer

Energy transfer in the contact area of the vibrating drum as well as vibration and movement perform-ance of the rollers are substantially influenced by the reaction force and the dynamic stiffness of the layers to be compacted.

During the vertical movement of the drums the static weight forces, the spring and damping forces of the rubber buffers, the centrifugal forces, the inertial forces and the contact force are effective, as shown in Fig. 20.

Fig. 20

Vertically directed equilibrium of forcesof the vibrating drum

The contact force contains the dynamic reaction forces of the base. Entering the contact force over the vibration path results in a force-path-diagram as shown in Fig. 21, in which the movement phases of compaction become apparent (example, Lit. 7, 8).

Part 1

21

The indicator diagram shows the ground contact force during compaction. The roller temporarily loses ground contact. During this phase of compac-tion the amplitude increases from 1.6 mm to almost 2.5 mm and the soil contact force to almost three times the static drum axle load. Due to the low soil stiffness and the low resonance influence of the static drum axle load both ground contact force and amplitude comply with the theoretical values at the beginning of the compaction process.

The indicator diagram enables an examination of energy transfer and soil stiffness. The hysteresis area between compression and expansion cycle shows the measurement for the energy transfer into the substrate. The area below the expansion curve reflects reactions to the drum. The inclination of the

compression curve ∆FB / ∆x is used to determine the resilient stiffness of the base.

Fig. 22 shows measured indicator diagrams for amplitudes of various sizes (Lit. 7, 8). If the roller is used with various amplitudes, the energy trans-fer changes in accordance with the diagram. As shown in the diagram, the maximum reaction force increases in a degressive way with increasing amplitude. It clearly shows that a most favourable nominal amplitude exists for any drum axle load and that a higher static linear load in combination with a given amplitude also increases the reaction force of the base. The vibrating mass can only fully transfer the vibration intensity to the substrate, if the static axle load is fully applied to the substrate as a pre-load.

On base layers with a low stiffness the vibratory roller will not lose ground contact when vibrating with a low nominal amplitude and if the maximum contact force does not exceed two times the axle load (Fig. 22).

When continuing to increase the amplitude or the stiffness of the substrate, the roller can no longer fully transfer its movement. Its dynamic resting posi-tion moves up, so that it jumps up with each revo-lution of the exciter shaft when certain limit values are exceeded. In this jumping condition a frequency proportion is generated, which is half or an integer

Fig. 21

Exchange of energy between roller/soil and dynamic resilient stiffness of the soil

Compression and expansion phaseduring the compaction process

Presentation of the soil contact force in dependence of the vibration path of the roller drum (vertical compo-nent) in the indicator diagram (Kröber 1988)

Fig. 22

Indicator diagram for increasing compaction and different amplitudes (example)


22

multiple of the originally shown vibration frequency. This operating condition remains stable and repro-ducible under steady conditions.

With a further increase of the vibration amplitude or the stiffness of the substrate the roller becomes unstable and starts to tumble. Under this operating condition non-periodic vibration movements develop around the longitudinal axis of the drum with fre-quencies depending on the natural frequency of the vibration system (frame / vibrating mass).

Part 1

23

3 Design types and applications for BOMAG compaction technology (Lit. 24 to 28)

3.1 Vibratory tamper

Vibratory tampers cause an impact compaction. The engine of the vibratory tamper drives a crank drive with conrod, which is clamped between two pressure springs. The vertical movement of the drive shaft results in a movement against the spring force. After a revolution the tamper plate lifts off the base and hits back after a 180 rotation of the crank drive. (Fig. 23 and 24)

Typical weights from 50 to approx. 100 kg. Fre-quency range approx. between 9 and 11 Hz (540 to 660 blows per minute).

An optimal compaction is normally achieved at fre-quencies around 10 Hz (600 blows per minute) with an amplitude range from 60 to 80 mm. Vibratory tampers are most suitable for applications in con-fined and difficult to access work areas, where only light compaction equipment can be used or rela-tively high and non-uniform layer thicknesses are required. Vibratory tampers are used for compac-tion of cohesive soils, mixed soils and gravely soils.

For applications in narrow trenches, e.g. pipeline or cable trenches, vibratory tampers can be fitted with special small tamper plates.

Fig. 24Design and equipment of the vibratory tamper

3.2 Vibratory plates/hydraulic plates

Vibratory plates normally work with frequencies between 55 and 90 Hz (3300 to 4500 revolutions per minute). The generated centrifugal forces are in the range between 25 and 86 KN (2.5 to 8.6 t). Machines are available up to weight of 700 kg.

In comparison with vibratory tampers the compac-tion performance of the plates widens their appli-cational versatility. Depending on the soil type the depth effect of a vibratory plate may be as favoura-ble as the depth effect of large vibratory rollers. The dimensions of the plates and especially the work-ing width can be adapted to various applications. Due to the development of quiet machines and a more efficient vibration insulation of the guide han-dles the latest vibratory plates are much easier to manoeuvre than older types.Vibratory plates are self-propelled or self moving (Fig. 25). A differentiation is made between plates which move only to one direction (Fig. 26) and plates with special controls to reverse the travel direction (Fig. 27).

Fig. 23Movement sequence of vibratory tampers


24

Fig. 25Movement sequence of vibratory plates

One-directional plates are equipped with only one exciter shaft. The amplitude depends on the mag-nitude of the unbalanced mass, the mass ratio between eccentric and vibrating parts as well as their centre of gravity. The maximum working speed, a design parameter for the development of such a machine, depends on the position of the exciter shaft and the position of the centre of gravity of the entire plate as well as on the ration of weight and centrifugal force. This enables also the working speed in forward direction. This working principle is applied to narrow plates with low weight.

Fig. 27

Design and equipment of the vibratory plate(controllable in forward and reverse)

BOMAG plates with reversible working direction use two exciter shafts with double directed vibration. The two exciter shafts with their eccentric masses work in opposed position, whereby the direction of the forces generated by the centrifugal force also change. This enables reversing of the travel direc-tion from forward to the opposite direction during compaction. Furthermore, this allows for a control-led change of the working speed and therefore also of the intensity of compaction per pass. Heavy vibra-tory plates work with an operating weight of more than 120 kg according to this principle. The reversal of the working direction enhances the guidance of the machine and eases work. Heavier plates are equipped with electric starters for easier starting of the diesel engines.

Another rationalisation of compaction work is achieved by coupling hand guided BOMAG vibra-tory plates with a high total weight. This coupling enables forward and backward movement as well as turning on the spot. This application enhances power and mobility during compaction, e.g. in foun-dation excavations and backfills around buildings as well as adjacent foundation objects. Heavy revers-ible plates are also used for compaction work in trenches. For these applications the ventilation and filter systems must be specially adapted, the drive system must be well protected and sufficient lateral space for work is required. For this type of work the

Fig. 26

Design and equipment of the vibratory plate (controllable in forward direction)

Part 1

25

machines are additionally equipped with dirt deflec-tors and fixed installations for lifting.

A new development is the steerable hydraulic plate with a vibrator system similar to the reversible mechanical vibratory plates. Similar to the reversible mechanical plates the steerable hydraulic plates are equipped with two counter rotating exciter shafts which are both fitted with an eccentric weight.

The main differences of the steerable hydraulic plate are the hydraulically driven exciter unit and the rear exciter shaft. This shaft is designed in a way that the parts of the split eccentric weight can be offset to each other. This generates a torque that enables the operator to control the machine with-out a steering handle, i.e. without direct contact to the machine, via a remote control. With this working principle the machine does not only move forward and backward, but can also be steered to right and left.

Fig. 28

Working principle of the hydrostatically controlledvibratory plate

Besides their possible use for standard applica-tions, hydrostatic vibratory plates with remote con-trol (Fig. 28) are available for difficult work areas, such as deep trenches. These systems with cable, infrared or radio remote control relieve the machine operator and contribute to safe work in unsupported trenches.

3.3 Hand guided vibratory rollers

Hand guided vibratory rollers are available in single drum version or as tandem rollers (Fig. 29 and 30). Both types are self-propelled with reversible travel direction.

The operator controls and steers the machines by means of a steering rod. Compared with plates and tampers the mobility of these rollers enhances the compaction work. These rollers are used for soil as well as asphalt compaction and most frequently for small area repair and patch work.


26

Design and equipment of the hand-guidedsingle drum vibratory roller Fig. 29

Design and equipment of the hand-guideddouble drum vibratory roller Fig. 30

Single drum rollers work with weights of 160 to 460 kg, high frequencies of 70 to 77 Hz (4200 to 4630 revolutions per minute) and amplitudes between 0.4 and 0.5 mm.

Hand guided tandem rollers have two drums of identical size with relatively small diameter. Each

drum is fitted with its own eccentric shaft. Both drums are driven, are connected by a rigid frame and are mechanically controlled by pulling or press-ing the steering handle. Tandem rollers are also available with hydraulic controls, which reduces the controlling effort.

Depending on the state of technology hand guided tandem rollers are available with mechanical travel and vibration systems as well as with hydraulic drive and hydrostatic vibration systems. The hydro-statically driven system offers smoother response when changing the travel direction, which is of spe-cial advantage when compacting asphalt.

The machines work to their optimum when used on small work areas, for the compaction of soil and, if equipped with a water sprinkler system, on asphalt. The rollers have a very favourable centre of gravity and therefore develop high traction force on uneven ground. Special designs are available for use on trenches and on slopes.

3.4 Tandem rollers

Tandem rollers have two drums of identical diam-eter, each equipped with a exciter shaft. These machines are powered by an air cooled diesel engine. Travel and vibration systems are hydrauli-cally driven. Single lever control and infinite speed regulation enable jerk-free acceleration and decel-eration.

Tandem rollers are available with hydrostatic artic-ulated steering, heavier versions alternatively with hydrostatic pivot steering. A differentiation is made between light and heavy tandem rollers.

Light tandem rollers

The use of light tandem rollers enhances the area output of the compaction process, because these rollers are have a higher mobility, are faster and more manoeuvrable than hand guided rollers. These roller types were developed for the compaction of asphalt and are therefore equipped with water sprinkler systems. They can, however, also be used for soil compaction.

Part 1

27

Light tandem rollers vary in the range between 1.5 and 4.5 t with working widths from 800 to 1380 mm (Fig. 31).

The most suitable working width can be chosen to match the site conditions. The static linear loads span from 8 to 15 kg/cm.

Theses machines are generally designed with double drum vibration and double drum drive and normally work with one frequency. By experience the machines in the range from 3 to 4.5 t have sufficient power to be used behind a paver with an output of 500 to 800 m2

222 per hour on surface courses or 300 to 400 m2

2 per hour on base courses, depending on the asphalt mixture. They are there-fore specially recommended for this type of appli-cation. Apart from this there is another type of application for these small self-propelled tandem rollers, which are available in different designs and successfully used.

Heavy tandem rollers

Heavy tandem rollers with operating weights between 6 and 12 t are used for the compaction of asphalt surface courses, asphalt binder courses, asphalt base courses and unbound base courses. They normally work with two amplitudes or two fre-quencies for an optimal compaction of different lift heights.

VARIOMATIC tandem rollers with the new directed vibration system described in T 1, para. 2.1.4 allow for an automatic adaptation of the effective ampli-tude to the material to be compacted.

Heavy tandem rollers are equipped with vibration automatic, a system which switches the vibration off when stopping the machine or when changing the travel direction, thereby avoiding transverse depres-sion and unevenness in the asphalt course.

Heavy tandem rollers are available with spit and non-split drums. Split drums reduce the risk of shov-ing and cracking when compacting in tight curves. Depending on the design one must differentiate between tandem rollers with articulated steering and pivot steering, which enable different modes of steering (Fig. 32).

Design and equipment of a light,articulated tandem roller Fig. 31


28

Heavy, pivot-steered tandem rollerwith split drums Fig. 32

Combination rollers

The combination roller is a combination of pneu-matic-tired roller and vibratory roller (Fig. 33).

The combination combines the advantages of the vibrating drum with the benefits of rubber tires, which have a kneading effect and seal the asphalt surface.

One axle of the combination rollers consists of a smooth drum, the other axle carries smooth rubber tires.

These rollers are also powered by air cooled diesel engines which drive the hydrostatic travel and vibra-tion systems. The rubber tires are driven in pairs by two hydraulic motors, ensuring adaptation of the left and right hand wheel pairs to the rolling speed differential when driving around curves.

Single lever control, hydrostatic power steering as well as vibration automatic ensure simple and safe operation of the large combination rollers.

Articulated combination roller with smooth drumand four rubber tires Fig. 33

3.5 Single drum rollers with smooth drum

Single drum rollers are self-propelled compactors with a front drum and rear tires (Fig. 34). These roller types are specially designed for soil compac-tion, where high tractive power and gradability is required besides excellent compaction work.

Front frame with drum and rear frame are con-nected by a central oscillating articulated joint. The rear frame carries diesel engine, drive elements and operator’s stand. The infinitely controllable travel systems works hydrostatically via the rear wheels. Single drum rollers are normally equipped with drum drive. The vibration drive also works hydro-statically. Single lever control and hydrostatic power steering enable simple operation. Depending on the tire tread the single drum rollers achieve a grad-ability of up to 45%. For even higher gradability the single drum rollers can be equipped with a stronger drum drive and an anti-spin-control (ASC). With these features the rollers can be used for gradients of up to 55%. Depending on soil or rock material the single drum rollers are used with smooth drums or with padfoot drum.

Part 1

29

Smooth drums can be used on most soil types, from rockfill to cohesive soils. The single drum roll-ers are generally equipped with all-weather tires, which ensure favourable traction and gradability under most soil conditions. The operating weights stretch from 2 to 25 t. The heavy single drum roll-ers are normally available with 2 amplitudes and 2 frequencies for thick and thin layers (Fig. 34).

In order to withstand extreme loads, e.g. during the compaction of rockfill, the drum must be of high strength and durability.

A long striven goal of research and development and a remarkable leap in technology was achieved especially with the newly developed VARIO vibra-tor exciters. These innovative self-controlling sys-tems detect the energy requirement and regulate the system automatically;see T 1, para. 2.1.4.

Design and equipment of a single drum rollerwith one vibrating drum Abb. 34

Attachment of vibratory plates:

The attachment of hydraulically driven vibratory plates to the single drum vibratory roller extents the range of applications and rationalises compaction work. The depth effect of the single drum roller is thereby combined with the favourable surface effect of the plate, thereby achieving a higher compaction output with less passes.With this combination the single drum roller com-pacts with the front drum and the vibratory plates attached to the rear at the same time (Fig. 35). The vibratory plates are driven by an additional hydrau-

lic pump on the single drum roller and work with an adjustable frequency of 32 to 50 Hz and a centrifu-gal force of max. 50 kN.

Single drum vibratory roller with hydrostaticallydriven vibratory plates attached Fig. 35

Another possible application is the efficient soil compaction in highway and transportation engineer-ing, urban foundation and civil engineering projects or such projects under confined spatial conditions. This work requires compact and extremely manoeu-vrable single drum rollers in the 7 t - class, which can be optimally adapted to the permanently chang-ing filling material while considerably reducing the vibration stress for nearby buildings at the same time. The use of the VARIOCONTROL system is therefore also recommended for these compact single drum rollers.


30

3.6 Single drum rollers with padfoot drum

Padfoot drums are designed for the compaction of cohesive soils and mixed particle soils with a rela-tively high water content. The imprints of the pad-feet contribute to a reduction of the water content. They are also used for the compaction of rockfill, in order to reduce the air void content and to crush large particles. As an adaptation to very moist, slip-pery soil conditions single drum rollers with padfoot drums are equipped with extremely profiled tires, similar to tractors, as a measure to enhance the traction power. These single drum rollers need a highly durable drive system. From the present point of view separate drives of drum and wheels should be standard.

BOMAG padfoot rollers are equipped with special teeth (Fig. 36). With their shape and in combination with vibration they should achieve a kneading and impact or crushing effect together with a favourable depth effect:

- Pyramid teeth (high studs, small contact areas, extremely steep flanks) for intensive kneading and compaction of cohesive soils,- Triangular teeth for crushing of hard rock by means of high tip pressure and splitting forces,- Triangular teeth with cutters in between for the splitting and crushing of brittle rock, whereby the cutters in between also prevent jamming of parti cles between the teeth (Fig. 37).

Single drum vibratory rollers withwith special teeth

Fig. 36

BW 225 with 120 triangular teeth and additional wear resistant tips, H = 200 mm

BW 225 with 100 pyramid teeth, H = 150 mm

BW 225 with 150 standard teeth, H = 100 mm

BW 225 with 100 triangular teeth and cuttersin between, H = 200 mm

Part 1

31

Crushing of claystone by special padfoot roller drum with triangular teeth and cutters in between

Fig. 37

The latest BOMAG class of heavy single drum vibratory rollers (BW 225, 18 t drum axle load, 80 kg / cm static linear load) is a special development for the compaction of rockfill material, extremely stony cohesive soils as well as high lift heights.

After compaction the teeth leave a structured sur-face (Fig. 38). In these impressions water can col-lect, which increases the water content of the soil when a new layer is placed. On the other hand the structure enlarges the surface of the soil, so that it can dry out more quickly during dry periods or by wind. In most cases it may be necessary to follow the padfoot roller with a smooth drum roller after a short period of time, in order to seal the open tex-ture

Compaction work with a single drum rollerequipped with a padfoot drum Fig. 38

Especially suitable are single drum rollers with an anti-spin-control to achieve the favourable tractive power in a controlled manner. These systems are of highest significance for an economical compaction when a high gradability of the machine is required (Fig. 39). Furthermore, this system enables safe operation on inclined areas.

High gradability during compaction workdue to the anti-slip system Fig. 39


32

3.7 Towed vibratory rollers

Towed rollers are characterised by a single drum with a powerful vibrator. The entire operating weight of the drum is used for compaction without any losses, because no tractive power is required. The operating weight may therefore be considerably lower than the operating weight of a self-propelled single drum roller (Fig. 40). However, the costs per hours for the necessary tractor unit are significantly higher than the costs for a self-propelled single drum roller.

Compaction work with a towed vibratory roller Fig. 40

Fundamental principles of vibratory compactionPart 1

33

Compaction of soil and rock in earthwork

1. Soil

1.1 Soil groups under engineering aspects (DIN 18196/4022)

Classification attributes:

For the description of engineering properties and their suitability according to DIN 18196 all soil types are classified in groups of almost identical material structure and similar characteristics.

The attributes of these groups are purely of mate-rial nature: Particle size fractions according to DIN 4022 (Tab. 2), mass proportions of particle size fractions, plastic characteristics, organic and cal-careous components.

The groups are identified by two identification char-acters each. The first character identifies the main soil types and the second character the properties of highest importance for engineering purposes. In case of fine particle soil types this is the degree of plasticity, for mixed particle soils the type of fine particle additives (silt, clay) and for coarse particle soil types the curve of the particle size distribution determined by the uniformity coefficient U and the curvature coefficient C.

The properties of the soil types within the corre-sponding group change due to various parameters, such as water content level of density.

Soils are classified by application of visual and manual testing methods, identical with those described in DIN 4022. Laboratory tests are sup-plementary used if visual and manual evaluations are not sufficient, and additionally particle size distribution (DIN 18123), consistency limits (DIN 18122), ignition loss and lime content.

Range/ Designation Symbol Particle size range mm Blocks Y 200 Stones X > 63 to 200 Gravel particles G > 2 to 63 Coarse gravel gG > 20 to 63 Coarse particle range Medium grav. mG > 6.3 to 20 (sieve particles) Fine gravel fG > 2.0 to 6.3 Sand particles S > 0.6 to 63 Coarse sand gS > 0.6 to 2,0 Medium sand mS > 0,2 to 0,6 Fine sand fS > 0,06 to 0,2 Silt particles U > 0,0002 to 0,06 Coarse silt gU > 0,02 to 0,06 Fine particle range Medium silt mU > 0,006 to 0,02 (Sediment particles) Fine silt fU > 0,002 to 0,006 Clay part. (finest) T < 0,002 Table 2: Particle size ranges acc. to DIN 4022

Part 2

34

Coarse particle soils:

Coarse particle soils are classified according to their fine particle fraction passing 0.06 mm sieve (less than 5%), the sand or gravel fraction and the particle size distribution (Fig. 41).

The particle size distribution is assessed on the basis of the cumulative proportions of the particle fractions and by means of the uniformity coefficient U and the curvature coefficient C. The prerequisites for a wide graded particle size distribution are met if U > 6 und 1 < Cc < 3

In all other cases the particle size distribution is a close or intermittently graded distribution.

Main group d in mm Group Symbol < 0,06 > 2,0 coarse particle < 5% > 40% Gravel, gravel-sand mixture GE GI GW soils < 40% Sand, sand-gravel mixture SE SI SW Particle <0,06mm: 5-40% > 40% Gravel-silt mixture 5-15% GU 15-40% GU mixed particle Gravel-clay mixture 5-15% GT soils 15-40% GT < 40% Sand-silt mixture 5-15% SU 15-40% SU Gravel-clay mixture 5-15% ST 15-40% ST > 40% Silt Ip < 4%1): light plastic WL < 35% UL medium plastic > 35-50% UM distinct plastic > 50% UA fine particle Clay Ip > 7%2): light plastic WL < 35% TL soils medium plastic > 35-50% TM distinct plastic > 50% TA organogenic soils > 40% Silt Ip > 7%3) WL = 35-50% OU soils with Clay Ip > 7%3) WL = 50% OT organic < 40% coarse, mixed particle soils with humus, OH OK admixtures calcarous, siliceous admixtures Peat, not to slightly decomposed Z = 1-54) HN organic soils Peat, decomposed Z = 6-10 HZ Mud F Filling Soil [...] Foreign substances A 1) or below A-line 2) and above A-line 3) and below A-line 4) Z Degree of decomposition

Table 3: Engineering soil groups acc. to DIN 18196 (main groups)

Part 2

35

Plasticity diagram (DIN 18196) Fig. 42

Examples of particle size distribution curves Fig. 41


36

Fine particle soils:

Fine particle soils are classified by the plastic prop-erties of the fines passing sieve 0.06 mm; the sub-stantial criterion is the plasticity, weighted on the basis of the water content at the liquid limit wL and the plasticity index IP = wL - wPPP. Basis for the clas-sification is the plasticity chart in Fig. 42.

The higher the water content of a fine particle soil, the less dimensionally stable is its mass or the easier it can be deformed. In this respect the soil is differentiated according to various states (of con-sistency):

Consistency Characteristic

solid breaks brittlesemi-solid crumbles when rolled stiff kneadablesoft easily kneadablepasty swells out between the fingersliquid not dimensionally stable

The states are by standard defined by means of test specific limiting water contents and classified with the help of identification numbers IC and IL (Fig. 43 and table 4).

Mixed particle soils:

Mixed particle soils (mixed soils) contain propor-tions of fine particle material, sand and gravel. The fine particle component is differentiated in silt and

clay with proportions of 5 to 15% passing sieve 0.06 mm and from more than 15 to 40%.

In dependence on the proportional composition and plasticity of the fine particle component the properties of mixed particle soils are classified between a cohe-sive and a non-cohesive soil mechanical performance.

The limiting value of 15% approximately marks the transition. Below this value the coarse particle frac-tions form a supporting granular skeleton, which has a substantial effect on the properties of the soil. This is actually a fluid transition within a range of 10 to 40% particles passing sieve 0.06 mm. The 40%-proportion separates the mixed particle from the fine particle soil types.

Organogenic and organic soils:

Organogenic soils and soils with organic admix-tures are classified according to the plasticity chart, as far as they are silts or clays; according to Fig. 42 they are located below the A-curve. In case of coarse and mixed particle soils a differentiation is made on the basis of the type of admixtures (humus, calcareous, siliceous).

Conditions Fig. 43

Conditions in the Liquidity index IL Consistency index IC

plastic range w – wP wL – w liquid below 0 pasty from 1.01) to > 0.25 from 01) to < 0.5 soft from 0.5 to > 0.25 from 0.5 to < 0.75 stiff from 0.25 to 02) from 0.75 to 1.02) semi-solid below 0 > 1.0 (to wS) 1) Liquid limit wL 2) Rolling limit wP

Table 4: Definition and classification of conditions

wL- wP

IL = = 1 - ICIP

IC = IP

wL – w=

Part 2

37

Characteristics (solely of fractions > 76.2 mm) Group Typical symbol designations Pure gravels Non-uniform particle GW „Well“ graded gravels and less than structure, „well“ graded gravel-sand mixtures 5% One particle size pre- GP „Poor“ graded gravels Gravels more <0,074 mm dominant, „poor“ graded and gravel-sand than 50% of mixtures coarse fract. Contaminated Silty gravel: >4.8 mm gravels The fine particle fraction GM „poor“ graded gravel- more than is silty sand-silt mixtures Coarse soils 12% The fine particle fraction GC Clayey gravel: „poor“ more than <0.074 mm is clayey graded gravel-sand-clay 50% of soil mixtures >0.074 mm Pure sands Non-uniform particle SW „Well“ graded sands and less than structure, „well“ graded sand-gravel mixtures 5% One particle size pre- SP „Poor“ graded sands Sands more <0.074 mm dominant, „poor“ graded and sand-gravel than 50% of mixtures coarse fract. Contaminated The fine particle fraction SM Silty sands: <4.8 mm sands is silty „poor“ graded sand- more than silt mixtures 12% Clayey sands: „poor“ <0.074 mm The fine particle fraction SC graded sand-clay is clayey mixtures Silts and very fine sands, rock flour, silty or clayey The fine particle fraction ML fine sands with low is silt plasticity Weak plastic silts Clays with low to medium and clays plasticity Liquid limit <50% The fine particle fraction CL gravelly or sandy clays, Fine soils is clay silty clays, more than light clays 50% of soil Organic silts and <0.074 mm OL organic silt-clays with low plasticity Silts and silty soils The fine particle fraction MH with medium to high Plastic and highly plastic is silt plasticity silts and clays The fine particle fraction CH Clays with very high Liquid limit >50% is clay plasticity OH Organic clays with medium to high plasticity Highly organic soils Dark color, odour, Pt Peat and other strongly spongy feel, fibrous organic soils texture Table 5: Soil classification „Unified Soil Classification System“ (USA)


38

USC-System:

The engineering soil groups in DIN 18196 comply to a great extent with the internationally used Uni-fied Soil Classification (USC-System) of the US Bureau of Reclamation (Tab. 5) and the AASHO-classification (Tab. 6). See also T 2, para. 1.4.3.3.

Table 6: Soil classification AASHO* (USA))

1.2 Earth engineering classification (DIN 18300)

Purpose of classification:

The classification is used for uniform tenders and accounting of quantities as well as for the planning and cost calculation for work and the use of machines. Soil and rock types are classified accord-ing to their level of difficulty during work. The term „work“ includes the work processes: loosening, loading, conveying, placing and compacting.

Classification characteristics:

The classification is based on soil and rock mechan-ical characteristics, independent from equipment technological performance values. For the level of difficulty for work the following essential criteria are used:

*American Association of State Highway Officials

AASHO A-1-b A-1-a Classification A-2-7 A-2-6 A-2-5 A-2-4 A3 A4 A5 A6 A-7-6 A-7-5

Unified Soil Classification GW OH CH GM-u GM-d MH OL GC CL SW ML SM-d SC SM-u GP SP Classification Broken by sight cohesive soils Sand Gravel material Shrinkage cracks large medium missing Vegetation rich strong medium light poor to non existent Condition if saturated with water very soft soft changing solid Condition dry solid changing rolling

Part 2

39

a) granulometric sizes: Fines passing sieve 0.06 mm, stones retained on sieve 63 mm, rocks > 0,01 and 0,1 m³b) plastic properties of the fines (plasticity index IP, consistency index IC, tenacity)c) water retaining properties and flow characteristicsd) mineral-chemical coherence (cementation)e) Strength of rock material acc. to qualitative characteristics

Classification:

Soil and rock are classified into 7 classes with respect to their condition during loosening. Topsoil is listed as an own class with respect to its special treatment, irrespective of its condition during loos-ening.

Class 1: Topsoil

Uppermost layer in the soil profile containing also humus and soil inhabiting life forms, besides e.g. mixtures of gravel, sand, silt and clay.

Class 2: Flowing soil types

Soil types of liquid or pasty consistency and difficult to drain.Class 3: Light to loosen soil types

Non-cohesive to slightly cohesive sands, gravel and sand-gravel mixtures containing up to 15% admix-tures of silt and clay (particle sizes passing sieve 0.06 mm) and maximum 30% rocks retained on sieve 63 mm up to a volume of 0,01 m³.Organic soil types with a low water content. e.g. solid peat.

Class 4: Moderately difficult to loosen soil types

Mixtures of sand, gravel, silt and clay with more than 15% of particles passing sieve 0.06 mm.Cohesive soils of light to moderate plasticity, which are soft to semi-solid, depending on water content,

and contain maximum 30% rocks retained on sieve 63 mmup to a volume of 0.01 m³.

Class 5: Difficult to loosen soil types

Soil types of classes 3 and 4, however, with more than 30% rocks retained on sieve 63 mm up to a volume of 0.01 m³.Non-cohesive and cohesive soils with maximum 30% rocks of more than 0,01 m³ to 0,1 m³ in volume.Distinct plastic clays of soft or semi-solid consist-ency, depending on the water content.

Class 6: Easy to loosen rock and comparable soil types

Rock types with an inherent mineral bonded coher-ence which are, however, excessively jointed, brit-tle, crumbly, slaty, soft or weathered, as well as comparable solid or stabilised cohesive or non-cohesive soils resulting from e.g. desiccation, freez-ing, chemical bonding.Non-cohesive and cohesive soils with more than 30% of rocks bigger than 0.01 m³ to 0.1 m³ in volume.

Class 7: Difficult to loosen rock

Rock types with an inherent mineral bonded coher-ence and a high structural strength and which are hardly jointed or weathered.Firmly bedded, non-weathered clay shale, gompho-lite shale, slag piles from steel works and similar.Rocks with a volume of more than 0,1 m³.


40

1.3 Geotechnical suitability of the soil types (Lit. 23)

1.3.1 Material and engineering properties

For soil groups with almost identical soil mechani-cal characteristics DIN 18196 contains information about the assessment of their engineering suitabil-ity.

In connection with the engineering assignment in Tab. 7, Fig. 44 shows the general assignment of the substantial soil mechanical properties.

Compactibility(V)Compaction level DPr

Packing density DOpt. water content

Plastic propertiesPlasticity,

mineral-chemicalcomposition,

water content, consistency

Granulometric propertiesParticle size range

Particle shapeParticle roughness

Soil / rock

Coarse Fine or mixed particle particle

Compressibility (Z)Deformation modulus EV

Stiffness index ES, swelling indexPorosity (D) Shearing resistance (S)

friction angle, cohesion

Erosionsusceptibility (E)

Frostsusceptibility (F)

Watersusceptibiloity (W)

Interrelationship between material and engineering properties Fig. 44

Slopes (cut, embankment, excavation pit) S-V-D-E-W-F Road subgrade Z-S-V-W-E-F Road embankment (foundation) Z-S-V-W-F Embankment subgrade (to a depth of 1.0 m) Z-S-V-W Foundation for embankments and bridges Z-S-V-D Back filling (bridges, constructions, pipelines and cables) S-V-D Earthroads and construction roads, base courses S-V-W-E-F Table 7: Engineering assignment of soil character-istics

Part 2

41

In contrast to the purely organic soils of groups HN, HZ and F, the soils of groups OU, OT, OH and OK (organogenic soils and mineral soils with organic admixtures) can only be used to a limited extent as material for earthworks, if their suitability has been exactly verified in an object and purpose related manner.

In general the soil parameters must be determined and applied on the basis of laboratory and field tests. For these investigations the state of the respective soil type and its possible change must be duly considered.

The standard or informative experience values in E DIN 1054 can be applied for the determination of characteristic soil parameters for non-cohesive and cohesive soils, if an exact assignment to the soil types of DIN 18196 is available and the condi-tions or limitations for the use of table 8a/8b and 9a/9b according to E DIN 1054 has been taken into account.

Soil type Symbol Packing Unit weight acc. to soil moist saturated under buoyancy DIN 18196 γk γk γ‘k [kN/m3] [kN/m3] [kN/m3] Gravel, gravel sand, sand GE, SE lose 16.0 18.5 8.5 tightly graded with U<6 med. dense 17.0 19.5 9.5 dense 18.0 20.5 10.5 Gravel, gravel sand, sand GW, GI, SW, SI lose 16.5 19.0 9.0 widely or intermittendly with 6<U<15 med. dense 18.0 20.5 10.5 graded dense 19.5 22.0 12.0 Gravel, gravel sand, sand GW, GI, SW, SI lose 17.0 19.5 9.5 widely or intermittendly with U>15 med. dense 19.0 21.5 11.5 graded dense 21.0 23.5 13.5

Table 8a: Experience values for the unit weight of non-cohesive soils (normative)

Soil type Symbol Packing Friction angle acc. to φk DIN 18196 [°] Gravel, gravel sand, sand GE, SE, GI lose 30.0 - 32.5 tightly, widely or intermittendly SE, SW, SI medium dense 32.5 - 37.5 graded dense 35.0 - 40.0 Table 8b: Experience values for the shearing strength (informative)


42

Soil type Symbol Condition Unit weight under acc. to soil moist saturated buoyancy DIN 18196 γk γk γ‘k Silt soils Anorganic cohesive soils with UL soft 17.5 19.0 9.0 lightly plastic properties stiff 18.5 20.0 10.0 (wL<35%) semi-solid 19.5 21.0 11.0 Anorganic cohesive soils with UM soft 16.5 18.5 8.5 medium-plastic properties stiff 18.0 19.5 9.5 (50%>WL>35%) semi-solid 19.5 20.5 10.5 Clay soils Anorganic cohesive soils with TL soft 19.0 19.0 9.0 lightly plastic properties stiff 20.0 20.0 10.0 (wL<35%) semi-solid 21.0 21.0 11.0 Anorganic cohesive soils with TM soft 18.5 18.5 8.5 medium-plastic properties stiff 19.5 19.5 9.5 (50%>WL>35%) semi-solid 20.5 20.5 10.5 Anorganic cohesive soils with TA soft 17.5 17.5 7.5 highly plastic properties stiff 18.5 18.5 8.5 (wL>50%) semi-solid 19.5 19.5 9.5 organic soils Organic silt OU a. OT pasty 14.0 14.0 4.0 Organic clay soft 15.5 15.5 5.5 stiff 17.0 17.0 7.0

Table 9a: Experience values of unit weight for cohesive and organic soils (normative)

Soil type Symbol Condition Shearing strength acc. to Friction Cohesion DIN 18196 φk Cl

k Cluk

[°] [kN/m2] [kN/m2] Silt soils Anorganic cohesive soils with soft 0 5 - 60 lightly plastic properties UL stiff 27.5 - 32.5 2 - 5 20 - 150 (wL<35%) semi-solid 5 - 10 50 - 300 Anorganic cohesive soils with soft 0 5 - 60 medium-plastic properties UM stiff 22.5 - 30.0 5 - 10 20 - 150 (50%>WL>35%) semi-solid 10 - 15 50 - 300 Clay soils Anorganic cohesive soils with soft 0 - 5 5 - 60 lightly plastic properties TL stiff 22.5 - 30.0 5 - 10 20 - 150 (wL<35%) semi-solid 10 - 15 50 - 300 Anorganic cohesive soils with soft 5 - 10 5 - 60 medium-plastic properties TM stiff 17.5 - 27.5 10 - 15 20 - 150 (50%>WL>35%) semi-solid 15 - 20 50 - 300 Anorganic cohesive soils with soft 5 - 10 5 - 60 highly plastic properties TA stiff 18.5 10 - 20 20 - 150 (wL>50%) semi-solid 19.5 50 - 300 Organic soils Organic silt OU a. OT pasty 0 2 - 20 Organic clay soft 17.5 - 22.5 2 - 5 5 - 40 stiff 5 - 10 20 - 150

Table 9b: Experience values for the shearing strength (informative)

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43

1.3.2 Geotechnical suitability for earthwork

1.3.2.1 Clays and silts

The suitability of fine particle soils for embankments depends on the load applied by the earth moving operations, the stability of the embankment slopes and the applied earth loads as well as the magni-tude of the inherent settlement of the embankment. The permissible placement water content resulting from these various conditions, must ensure opti-mal compaction; otherwise improvement measures including soil exchange or soil redistribution to lower dams and landfills, stabilisation with lime or cement, or a sandwich construction method with coarse par-ticle materials may be necessary (Fig. 45).

Soil stabilising with lime to enhance the compaction properties Fig. 45

Clays and silts form the main groups of cohesive soils. They differ strongly in particle fineness, min-eral constituents and the plasticity resulting from this. Their soil mechanical suitability for earthwork and embankments is decisively limited sensitivity against water and weather during loosening, load-ing, transport, placement and compaction. The plas-ticity dependent water absorbing capacity of these soils causes solid to pasty-liquid conditions (con-sistencies) This results in a extremely sensitively changing deformation and strength performance.

Silts and clays of low plasticity (wf < 50%, lP < 15%), the consistency of which drops strongly immedi-ately when absorbing stratum water, percolating water, precipitation water or the accumulated water

from frost and thawing periods, show a particularly critical sensibility and may soften and erode down to a considerable depth.

Due to their “toughness” (adhesive strength) the distinct plastic soil types are very difficult to process and compact. On the one hand they are less sen-sitive to water and erosion, but on the other hand they swell when absorbing water or when relieving the load if they contain clay materials with a swell-ing capacity (e.g. opaline and ornoite clays). During this process these materials develop moderate to high swelling pressures when the free deformability is inhibited.

The use of silts and clays with gypsiferous con-stituents shall be avoided because of the extreme swelling properties of the gypsum. If this cannot be avoided because of economical reasons, the place-ment shall be performed under the following condi-tions:

- the gypsiferous constituents in the filling material shall not exceed 10% by volume,- the gypsiferous material shall be evenly distributed in the filling material and compacted under dry weather conditions.

Solid clays may destrengthen similar to mudstone, especially as a result of repetitive dry/wet-cycles or frost/thawing-cycles. The resulting cracky or crum-bly structures increase the depth of water infiltration and softening.

Due to the above mentioned soil mechanical char-acteristics silts and clays are only suitable for earth-work if they are applied in dry weather with the optimum water content for compaction and without subsequent softening. Because of their general deformation sensitive properties and their potential inelastic deformation under permanent load, espe-cially in case of a distinct plasticity, the placement of these materials shall be restricted to such areas in earth or dam constructions which are less stressed by own weight or external forces.


44

In subgrade areas under carriageways down to a depth of 0.6 m these materials shall only be used if the demands for optimum placement water con-tent and plasticity characteristics of w<50% and/or l<15% and CBR>10% (after two days of immer-sion at a degree of compaction of at least 95% of the standard density) are met. With these criteria it is intended to permit only such soils in areas sub-jected to traffic loads, the settlement of which sub-sides relatively quickly and which have at least a short-term stability in case of precipitation.

Rules of thumb for the limiting values of the place-ment water content w in dependence on the water content wPp at the plastic limit, e.g.: w ≅ wP + 2 in % or w ≅ 1,2 bis 1,3 · wPp depending on soil type.

As far as permitted by the water contents, silts and clays may also be used by application of the sand-wich method using suitable gravel sand mixtures or rock materials or mixtures with such materials in form of well graded and well compressible mixed soils. However, these improvement and placement measures must also be combined with dry weather periods. With an appropriate optimum compaction the inherent settlements of such dams will be lower than the settlements in embankments without improved soils.

During the placement of silts and clays the following reactions must also be taken into consideration:

- With especially sensitive soil structures disturbances and collapses of these structures with the related strength losses may result from overcom paction when placing the filling material in layers. The limit criteria for such a performance must be examined within the scope of the suitability test.

- Under static or dynamic load action low permeability and a relatively high degree of saturation cause the development of strength reducing excessive pore water pressures which may lead to disjoining deformation or at least to long-term consolidation settlements. Such excessive pore water pressures also develop under construction site traffic.

1.3.2.2 Sands and gravel

The mechanical properties of sand and gravel mix-tures are similar to those of particulate media consisting of individual particles of more or less dis-similar size, loosely joined to a granular stratifica-tion structure with large pore spaces or with pore filling constituents forming a dense-graded stratum structure. With grain rearrangements this structure can adopt either a loose or a dense stratum (distur-bance or compaction). Particle mixtures consisting of individual particles of more or less similar size form highly porous granular structures, whereas mixtures with widely graded particle sizes form dense-graded structures.

Dense structures provide a considerably higher number of contact faces for friction and interlock-ing than loose structures. Their arrangement there-fore has a higher stability or self support; they are less deformable. Their resistance against shearing stress (shearing resistance, shearing strength) is mainly based on the friction and interlocking resist-ance of the individual particles. Their resistance against pressure and shearing strains and their inherent stiffness (modulus of deformation) there-fore rises with increasing level of compaction.

Apart from this, the friction and interlocking resist-ances are substantially influenced by the roughness and the shape of the individual particles, whereby rough surfaces and angular particle shapes enhance these resistances, in comparison to smooth and rounded particles.

Sands and gravel are generally suitable for earth-work and embankments (Fig. 46), with essential gradual differences in the mechanical strength and deformation properties caused by the described properties of the particulate media. The more non-uniform the composition and grading of the granular mixtures, the denser and mechanically stable they can be compacted. Their mechanical properties are indeed less dependent on the water content, but a favourable compaction water content (w = wPr) eases the particle rearrangement to stable mixtures during compaction.

Part 2

45

The particle rearrangement to a more dense struc-ture can be most effectively achieved by vibration energy if frequency, amplitude and vibrating mass are adjusted to the particulate media, lift height and stiffness of the base in such a way, that machine and ground do not vibrate in resonance, see T 1, para. 1.2

On the free surface, where the inherent tension is relatively low because of the missing applied load and interlocking of particles, loosening of the soil caused by the shearing stress of the machine and the drying of the mixture cannot be avoided during compaction. These effects can be reduced when compacting the next lift or by adding low quantities of fine particle soil.

During the compaction of very uniformly graded sands a substantial particle rearrangement can hardly be achieved without a refinement of the par-ticles at the same time. Theire compaction char-acteristics does therefore not indicate an essential influence of the water content. Nevertheless, due to the temporarily occurring “apparent cohesion”, these size fractions can be compacted to a more self-supporting and stable structure than in dry con-dition. In dependence on the proportion of fine sand and silt these sands respond very sensitively to water and wind erosion.

The hardness of the individual particles (particle strength) is particularly determined by the mineral constituent. Particle refinement caused by particle

destruction and abrasion as a result of mechanical impact during placement and compaction occurs especially in case of low hardness. These particle refinements change the soil mechanical properties of the mixture, such as permeability, frost suscepti-bility, compaction characteristics.

The non-cohesive sand and gravel mixtures gener-ally, and especially in wet condition, show a trend towards segregation, e.g. during excavation, when picking up and tipping these mixes, during haulage and distribution. Since the segregation may lead to inhomogeneous compositions and changed soil mechanical properties, this must be counteracted by wetting and, during placement, by controlled mechanically assisted remixing.

1.3.2.3 Mixed particle soils

The large group of mixed particle soils covers all mixture variants of sand, gravel, silt and clay within the limits of the fine particle fraction between 5 and 40 M-% passing sieve 0.06 mm according to DIN 18196.

Their suitability depends mainly on the main constit-uent effective for placement and compaction (Fig. 47). If the coarse particle components form the supporting grain skeleton, compacted mixtures of excellent stability can be achieved. However, due to the fine particle components these mixtures show a weather dependent performance with regard to earthwork and site traffic.

Compacting a tightly graded sand with a combination of single drum roller and vibratory plates Fig. 46

Compacting a gravel-silt mixture in 40 cm-layers using 19 t single drum rollers Fig. 47


46

If the fine particle components form the main matrix of the mixture, the suitability is also subject to sim-ilar restrictions as described under para. 1.3.2.1. With the exception of the uppermost embankment area down to a depth of 0.6 m below the formation, individual rocks with a size of 0.01 to 0.1 m³ can be embedded in the fine particle matrix, depending on the thickness of the lift to be compacted, as long as this does not obstruct the compaction.

Mixed particle soils also very often occur during the excavation of weathered top stratum. Depending on weathering and composition of mixture these soils normally have strong water absorbing, weathering and erosion sensitive properties; this is especially apparent with silt and/or clay containing sand mixtures. In earth-moist condition and well com-pacted they posses a favourable short-term stability with medium shearing strength, but remain highly deformable under load application. Water absorp-tion normally causes a quick, strength reducing transition to a soft or pasty consistency. Compressi-bility and shearing strength improve with increasing gravel fraction in the mixtures with at least medium-dense bedding.

1.4 Compaction characteristics of soils (Lit. 13, 23)

1.4.1 Compaction parameters

The state of compaction of soils is determined using the density values ρ, the void content n or the void ratio e. Fig. 48 shows the interrelations of these values schematically for the soil element and the unit cube.

Schematic presentation of compaction parameters of a soil element Fig. 48

Bodenelement

Unit cube

V

Vp

Vs

Air

Water

Solid mass

Air

Water

Solid mass

1

1

e

n

ρa = 0

ma

Va

ρd =

md

V

ρw =

mw

Vw

ρs =

md

Vs

The individual parameters are defined in the appen-dix and can be converted according to appendix A 2.

Particle density ρs, water content w and saturation index Sr are needed as auxiliary values for the calculation. The specific gravity values identify the mass forces per volumetric unit which are used to determine applied soil loads and earth thrusts for earth static calculations.

The values ρ, n and e are referred to limiting values as reference values in order to be able to define and categorise the compaction state of the soil numeri-cally. The following values serve this purpose:

ρd DPr Compaction level DPr = . 100 in % ρPr

max n – n ρd – min ρ l + min e D Packing density D = = = . ID max n – min n max ρ – min ρ l + e

max e – e max ρd ID referred ID = = . D packing density max e – min e ρd

va

vw

ea

ew

ma

mw

md

ρa

ρw

ρs

na

nw

Part 2

Soil element

47

Engineering requirements for compaction in earth-work and highway and transportation engineering are generally specified with the degree of compac-tion DPr Pr. These parameters define the ratio of dry density ρdd to Proctor density Pr numerically ρPr.

The Proctor density is the maximum dry density max. ρPr (Fig. 49) that can be achieved by the lab-oratory test described in DIN 18127. The volume related compaction work is A = 0,6 MNm/m³. The modified Proctor density mod ρPr Pr is used for special investigations and is determined by a bigger volume related compaction work of A = 2,75 MNm/m³ using the method described in DIN 18127.

Proctor test to determine the compaction characteristics of a soil Fig. 49


48

With these reference values from international earthwork practice the compaction effect that can be achieved on a certain soil is simulated in a labo-ratory test; for functional interrelationship and soil physical significance see T 2, para 1.4.2.

Besides the degree of compaction DPr the compress-ibility of coarse particle soils can also be character-ized by the limit values of loosest and the densest level of compaction. Since the bedding orientations illustrated for balls of identical shape can only be applied to natural grain-type material deposits con-sisting of particles with irregular sizes and shapes in an idealised manner, the limit values for the den-sity must be determined by standard laboratory tests (DIN 18126). The parameters D and ID can be converted to one another using the following equa-tions:

1 + min e D = ID .

1 + e 1 – min n ID = D .

1 – n The level of compaction IDD is subdivided into

0.00............................... loosest density 0.00 – 0.35.................... loose 0.35 – 0.50.................... medium dense 0.50 – 0.70.................... dense 0.70 – 1.00.................... very dense 1.00............................... densest density

The parameters DPrPr and ID can be approximately assigned as follows

DPr = 1 ........................... 0.50 < ID < 0.85 DPr = 0.97...................... 0.40 < ID < 0.65 DPr = 0.95...................... 0.30 < ID < 0.55

The lower limiting values apply for gravelly, the top limits for sandy mixtures.

1.4.2 Compaction characteristics

1.4.2.1 Functional interrelationship

The compaction characteristics are specified as interrelationship between compaction work A, dry density ρd and water content w, schematically pre-sented in Fig. 50.

b) Interrelationship between dry density ρd, water content w and saturation level Sr air void proportion na Fig. 50

a) Interrelationship between dry density ρd, water content w and compaction work A

Dry

den

sity

ρd

w1w01 w02

wl wll

max ρd2

max ρd1

Water content w

Sr = 1,0

A 2 >

A 1

Sr = 1,0 n

a = 0

ρd

ρd

na =0,8

Sr =0,2

A 1

Part 2

49

With progressing compaction work A2 > A1 the characteristic curve shifts in such a way that ρd increases while w decreases; the increase of ρd thereby drops with progressing compaction work in accordance with a logarithmic function. A certain density ρd < max. ρd is possible within 2 limiting water contents w‘ und w‘‘. With w < w‘ compaction is possible when increasing work A, however, this is no longer possible with w > w‘‘.

For certain soil groups the peaks of the compaction curves determined for compaction work of various size are approximately located on a specific satu-ration line of hyperbolic shape (example see Fig. 52). This line thereby characterises an optimal satu-ration of the pores opt Sr r as a value independent from compaction work A. With saturation below the optimum the compactibility becomes moderate and above the optimum it becomes impossible, if the pores are saturated.

The compaction of soils in the respective optimum range of water content has an essential soil physi-cal effect on the soil properties relevant for engi-neering purposes; this applies especially for the fine and mixed particle soil types (T 2, para. 1.4.2.3 and 1.4.2.4) such as

- minimum permeability at wPrPr (+ 1%), increased permeability on the dry side of up to 2 powers of ten, on the wet side up to five times in comparison to the minimum possible,

- minimum compressibility of the soil; on the dry side subsidence (settling collapse) during heavy precipitation possible. Strong com pression for w > wPr due to the low consistency and excessive pore water pressures,

- maximum shearing strength of the soils as (wPr – 2%); decrease of shearing strength on the dry side because of the low density, on the wet side because of a too high saturation and excessive pore water pressures.

The properties of the fine and mixed particle soil types are therefore highly influenced by the propor-tion of air voids naa. If these soils are too dry during

placement, lumpy conglomerates with a high air void content will form. These can then not be suf-ficiently and evenly compacted. If these soils with their high proportion of air voids are subsequently softened by the infiltration of water, e.g. because of precipitation, their shearing strength will drop. The load bearing capacity drops leading to settlements or subsidence. If the fine particle and mixed particle soils are compacted at a too high water content, a rubbery deformable performance will occur. The soil subsides after compaction. On the other hand, if compaction takes place at a too dry water content, large air voids will remain between the crumbs, so that subsequent wetting will also result in extreme deformations.

1.4.2.2 Coarse particle soils

Fig. 51 shows characteristic compaction curves from Proctor tests on coarse particle soils. Both the density and the influence of the water content rise with increasing non-uniformity of the mixtures; the curves take an increasingly steeper course and limit the narrowing optimal ranges. In these cases the maximum values and the curve sections w > wPrPr can no longer be uniquely defined in tests. The opti-mal saturation index opt Sr can then be used as an auxiliary criterion for the establishment of the maxi-mum dry density ρPrPr and the related optimal water content wPrPrPr.

The intersecting points of the saturation line opt Sr with the compaction curves identify these values with sufficient proximity. According to a statistical evaluation of test results the optimal saturation index for gravel-sand-mixtures opt Sr = 65%; Lit. 15.

Fig. 51 also shows very flat curves for uniformly graded sands. From this it can be assumed that their compactibility is low and hardly influenced by the water content.


50

Proctor curves for various gravels and sands(Compaction work A = 0,6 MNm/m3) Fig. 51

Depending on the degree of compaction DPr Pr the air void content n has approximately the following size:

1.4.2.3 Fine particle soils

Compaction of fine particle soils is only possible if a proportion of compressible air voids exists. Due to the incompressibility of water, soils saturated with water cannot be compacted, as long as they are not drained at the same time.

The compaction characteristics depend on water content, air content, plasticity and particle size dis-tribution. Fig. 52 shows characteristic compaction curves from Proctor tests: these reveal

- the density decreases with increasing plasticity; it is normally lower than for coarse particle soils

- the water binding ability of fine particle soils depends on their plasticity. During compaction their sensitivity to changes in the water content increases with decreasing plasticity.

The optimal water content rises with increasing plasticity and the range widens, in which a certain density can be achieved (limit water contents). Silts therefore have a narrower range of optimal water content and are more sensitive to weather influ-ences than clays.For various degrees of compaction DPr the air void contents n have approximately the following size:

The optimal water content can be estimated with the help of the plastic limit wp. For lightly plastic soils it can be specified with 2-4 % and for distinct plas-tic clays with 3-6 % below the water content at the plastic limit.

DPr = DPr = DPr = 100 % 97 % 92 % Gravel-sand mixtures, silty 14 – 20 17 – 22 18 – 24 Gravel-sand mixtures 20 – 28 22 – 30 24 – 32 Sands 28 – 36 30 – 38 32 – 39

Tab. 10: Estimation of the void proportion n for variousdegrees of compaction

Dry

den

sity

ρd

in t/

m3

sr = 1,0 (ρ

s = 2,65 t/m 3

DPr = DPr = DPr = 100 % 97 % 92 % Silts, sandy, gravely 23 – 27 25 – 29 27 – 31 Silts and clays low plastic 27 – 36 29 – 38 31 – 39 Clays, medium to distinct plastic 36 – 42 38 – 44 39 – 45

Tab. 11: Estimation of the void proportion n for variousdegrees of compaction

Proctor curves of various fine and mixed particle soils(Compaction work A = 0,6 MNm/m3) Fig. 52

sr = 1,0 (ρ

s = 2,70 t/m 3

Dry

den

sity

ρd

in t/

m3

Part 2

51

Fig. 52 shows that the air content na is approximately 5 % in the range of the curve maximum.

With increasing water content the fine particle soils change from solid via semi-solid, stiff and soft to the pasty consistency (condition). The strength decreases in the same sequence.

Tab. 12 shows that, at a degree of compaction of DPrPr = 100 %, distinct plastic clays have a semi-solid to solid consistency (lc > 1), but that soils with medium and low plasticity can already change to a stiff-plastic consistency (0,75 < lc < 1). At compaction degrees of DPr < 100 % the Ic-values corresponding with the top limit water content may already be very low; e.g. at DPr = 97% a soil can already reach the soft-plastic state and at DPr = 92 % it may even reach the transition to the pasty consistency.

1.4.2.4 Mixed particle soils

The compaction of mixed particle soils is substan-tially influenced by the mixing ratio of the fine and coarse particles, the water and air void content of the fine particle constituent as well as by the parti-cle size distribution and the plasticity of the fines.The Proctor density ρPrPr increases almost directly proportional with the coarse particle fraction and reaches peak values at 5 to 30 % fines. The more uniform the grading of the coarse particles, the higher this optimal fines proportion (fundamentals Lit. 14).

1.4.3 Relations between compaction and deformation parameters

1.4.3.1 Test dependent deformation parameters

The load bearing and deformation characteristics of soils are described by test, load and stress depend-ent deformation moduli, modulus of subgrade reac-tion or strength magnitudes.

Besides the actual compaction parameters (DPr, ρ, n, e) these deformation parameters are also used for the identification of the required compaction quality and the achieved level of compaction. Some of these deformation parameters are also most suitable as auxiliary dimensioning values for the design of pavements. This includes quasi-elastic deformation moduli from loading and relieve cycles under static or dynamic load as well as various empirical deformation resistances from penetrom-eter and punch tests (e.g. California Bearing Ratio CBR).

The statistic and dynamic deformation moduli of soils are determined as tension dependent values on the basis of the pressure deflection lines from load tests, the empirical deflection resistances are values depending on special test conditions.

Since the deformation parameters are very often correlated with compaction parameters in the prac-tice of soil compaction, here a brief description of the definition of less common values:

(1) Deformation modulus Ev

During plate bearing tests with static loads accord-ing to DIN 18134 the deflection of the soil surface under a rigid circular load plate with a diameter of 300 mm is determined. The load plate is centrally and vertically loaded in load stages and normally subsequently relieved step by step; further identical supplementary load and relieve cycles may follow (Fig. 53).

Soil type Consistency index lc DPr = 100 % DPr = 97 % DPr = 92 % Clays with distinct plasticity 1,3 – 1,0 1,2 – 0,9 1,1 – 0,8 Clays with medium plasticity 1,9 – 0,9 1,4 – 0,7 1,0 – 0,5 Silts, clays with low plasticity 2,1 – 0,9 1,8 – 0,7 1,0 – 0,5 Tab.12: Consistency indices for clay and silt soils with compaction levels DPr < 100 %


52

Principle of a static plate bearing testwith pressure-settling curve Fig. 53

During this plate bearing test the deformation mod-ulus Evv (resilient modulus) is normatively calculated on the basis of the pressure deflection line for the first and the repetitive load cycles as incline of the secant between points 0.3 σmax und 0.7 σmax accord-ing to

Ev = 1.5 r ∆σ/∆s [MN/m²]

This formula is based on the theory of the surface deflection of an elastic isotropic half-space under a centrally and vertically loaded, rigid circular plate.

(2) Modulus of subgrade reaction ks

For the calculation of the modulus of subgrade reaction ks used for the design of concrete pave-ments of highways and airports the compression stress σο#,, which complies with a mean deflection of s = 1.25 mm, is measured with a load plate of 762 mm in diameter. The modulus of subgrade reaction is calculated as follows:

ks = σο /s [MN/m²]

(3) Dynamic deformation modulus Evdv (resilient modulus)

In comparison to the static plate bearing test the dynamic plate bearing test is an accelerated test method. The test is applied for an indirect or com-parative verification of the load bearing capacity and compaction of test areas in a simple way. The dynamic deflection modulus Evd is determined on the basis of a defined impact load applied to the soil by a light falling weight. Its value is calculated on the basis of the maximum force F measured at the impact of the falling weight on the plate and the set-tlement amplitude s of the plate using the equation

Evd = 0,75 . d .

Set

tling

in m

m

Part 2

max σmax s

53

σ = Test pressureσs = standardised pressure at penetration depth: 0,25 mm σs = 7,03 MN/m² 0,50 mm σs = 10,55 MN/m²

(4) California Bearing Ratio CBR

In the CBR-test the pressure generated by a cylin-drical pressure punch pressed into the soil with uni-form speed down to penetration depths of 0.25 to 0.5 cm is determined:

CBR = . 100 in %

Principle of the dynamic plate bearing test (light falling weight unit) with force-path diagrams

Fig. . 54


Principle of the CBR-test with with punch pressure penetration curve Fig. 55

σσs

54

1.4.3.2 Soil specific interrelationships

Between the compaction parameters (DPr, ρn, e, D, ID) and the deformation parameters described in T 3, para. 1.4.3.1 extremely scattering soil physical interrelationships do exist. These are, on the one hand, caused by load and tension dependent elas-toplastic deformation characteristics, and on the other hand, by a series of soil and test specific influ-ence factors.

1) Coarse particle soils (sands, gravel), which are characterized by non-cohesive properties, always show a close dependence Ev = f(DPr) for only one specific particle mixture. The deformation modulus Evv, of a single sized sand, for example, is considerably lower than for a sand-gravel-mixture graded according to the square parabola, at an identical degree of compaction. If the pore content n is used as a parameter, this interrelationship can be transferred to a general closer form, as shown in Fig. 57; (Lit. 15). Calculating the quotient of the deformation moduli Ev2/Ev1 on the basis of the two compensa- tion curves shown in the illustration, results in the interrelationship presented in Fig. 57. The size of this quotient enables a conclusion on the remaining plastic deformability after compaction; besides others, this value indicates whether or not the Ev2-modulus results substantially from the compaction caused by the initial load.

Interrelationship between EV1-or EV2-modulus andair void proportion for sands and gravel sands Fig. 56

Dependence of the ratio value of the des deformation moduli EV2/EV1 on the air void proportion for sands and gravel sands Fig. 57

The water content has hardly any influence on the deformation resistance of non-cohesive soils. In Fig. 58 this is illustrated for the CBR-index in the function CBR = f(n, Sr) for saturation coefficients 35<Sr<65%. This illustration also shows that non-uniform gravel-sands can have a higher deforma-tion resistance than uniform mixtures, even with an identical pore content; this applies for parabolic or skip graded gravel-sands with non-uniformities in the medium particle size range; (Lit. 15).

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55

Relation between deformation resistance CBR and air void proportion n in dependence on the saturation index Sr 1 intermittent, 2 continuous Fig. 58

2) The deformation modulus Evv for fine particle soils, which is characterized by cohesive properties, is mainly influenced by the consistency or the water content. The Ev-modulus may also be very high with a low water content, if the density is low; vice versa it can be considerably reduced at high density by subsequent water absorption of the soil. This means that Ev on its own does not provide sufficiently reliable information about the quality of compaction.

The effect of the water content on the Ev-modulus can be detected e.g. via the consistency index Icc; the following is an approximate assignment

Der Einfluß des Wassergehalts auf den Ev-Modul läßt sich z.B. über die Konsistenzzahl Ic erfassen; näherungsweise besteht folgende Zuordnung

Tab. 13: Approximate assignment of Ev-modulus and consistency index IC

Tab. 14 contains experimentally evaluated limiting values of different deformation values for various degrees of compaction DPrPr. These values overlap considerably because of the variable water con-tents and conditions that plastic soils may have at compaction degrees DPrPr of identical value. This again demonstrates that the Ev-modulus (or any other deformation parameter) on its own is no qual-ity criterion for the compaction, but that, vice versa,

DPrPr on its own can not be a characteristic feature for the deformation performance. The proposition of these values can only be improved when including the water saturation Srr or the air content na in the evaluation.

3) According to T 2, para. 1.4.2.4 the main characteristic of mixed particle soils is the fact that their deformation properties are substantially based on the water content of the fines and the proportions of the coarse and fine particle fractions.

Tab. 15 shows a qualitative classification of the deformation performance of compacted mixed particle soils. Here the evaluation depends on the condition of the fine particle fraction and on the proportion of fine particles passing sieve 0.06 mm and coarse particles retained on sieve 2 mm.

Group 1 covers all sands and gravel with low pro portions of fines < 0.06 mm. Group 2 includes more or less uniformly graded sands with more than 15% < 0.06 mm, which have deformation moduli similar to sandy clays, at higher water contents. Besides the fine particle silt and clay soils group 5 also includes mixed soils with sand and gravel proportions of up to 40 %, which perform like cohesive soils. Groups 3 and 4 cover the range in between. Their deformation performance depends on the condition of the fines. In dried condition mixed soils of groups 2 to 5 may have very high deformation moduli.

Ev2 > 15 MN/m² Ic > 0,8 > 20 MN/m² > 0,9 > 80 MN/m² > 1,0 > 45 MN/m² > 1,2

Compaction level DPr 100 % 97 % 95 % 92 % Deformation modulus Ev1 MN/m² 6-56 5-38 4-11 1,5-19 Ev2 MN/m² 15-69 14-66 8-28 3.0-32 CBR-value % 6-30 4-22 2-18 0-12 Stiffness modulu E1 N/mm² 8-18 15-20 7-27 7-24 Load 0.2-0.4 N/mm² Pressure strength σB N/mm² 0,3-1,0 0,3-1,1 0,3-0,7 0,1-0,3 Shearing strength Level 11-28 11-27 10-30 8-29 N/mm² 0-0,45 0-0,35 0-0,33 0-0,26

Tab. 14: Deformation parameters for compacted fine particle soils(Degree of comp. DPr < 100 %, air content na < 12 %)


56

1.4.3.3 Relationships to international soil classifications

Fig. 59 shows relationships between various test empirically evaluated soil parameters in correlation with internationally used soil classifications.

Due to the inclusion of the soil classification accord-ing to DIN 18196 it is possible to bring the parame-ters almost to a soil specific compliance with foreign classification system. However, in-situ tests for the direct evaluation of these parameters cannot be replaced by these assignments.

Soil classification (USC*/DIN)and load bearing values Fig. 59

*Unified Soil Classification

MN/m2

Group Paricle prop. [%] Consistency Ic of the fines (silt, clay) d<0,063 mm d > 2 mm Ic > 1 0,75 < Ic < 1 Ic < 0,75 1 a < 15 a > ³ 0 ¡ ¡ ¡ 2 15 < a < 60 a < 30 ¨1) 3 15 < a < 40 a < 30 ¡1) ¨ 4 40 < a < 60 a > 30 ¨1) 5 a > 60 a < 40 1)

1) additional requirement: air void content na < 12% Deformation performance: O as with non-cohesive, coarse particle soils (sands, gravel, blocks) as with cohesive, fine particle soils (silt, clay) ¨in appropriately compacted condition between O and

Tab. 15: Evaluation criteria for the classification of the deformation performance of mixed particle soils

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57

2. Rock (Basic Lit. 12, 16)

2.1 Classification of rock (overview)

Rock types are differentiated according to genetic-stratigraphical and petrographical proper-ties. According to their origin they are classified as

2.1.1 Congealed rock (magmatic rock)

- Volcanic igneous rock, e.g. trachyte, andesite, basalt, porphyry, dolerite- Dyke rock, e.g. pegmatite- Plutonic rock, e.g. granite, syenite, diorite, gabbro

As extrusive igneous rock the volcanic igneous rock originates from the flow of magma that has been forced by gas and tectonic folding pressure to the surface of the earth where it finally solidified. Dyke rock was formed by the flow of rock that solidified under the surface of the earth in open crevices, chimneys and joints. Plutonic rock solidified in very deep depths under high pressure.

2.1.2 Sedimentary rock

- Clastic sediments, e.g. sandstone, greywacke, mudstone, slate, tuff- Chemical sediments, e.g. limestone, dolomite, salt, anhydrite, gypsum, chalk- Organogenic sediments, e.g. coal, peat

Sedimentary rock originates from weathered rock material that has been displaced by water, wind or glacier and deposited in the sea or at land. Solid-ification was caused by chemical or organogenic bonding or by pressure.

Some sedimentary rock was formed under special formation conditions:

Calcareous sinterIn the area of the springs emerging from the cal-cerous terraces and over high raised ground water calcarous crusts are formed by the dissolved lime in the water; these are known as alm, travertine or

tufa.Salt and gypsumSalt and gypsum have formed under hot and dry cli-matic conditions in sea arms. They are embedded in various types of rock (e.g. Raibler layers, lower triassic). Their presence is identified e.g. by sink-holes and dolines.

Limestone and dolomiteIn the warm sea fine slurries have initially been formed from calcareous spar, algae and plankton. Their alteration to limestone occurred chemically with a distinct stratification and enclosed shell res-idues from ammonites, snails, oysters and coral stocks.

The dolomites are of similar origin. Besides calcium carbonate they also contain magnesium, are mostly more brittle than limestone and change to grush under weathering.

Biogenetic or organogenic sedimentsAbsorption of substances dissolved in water by organisms and deposition in their skeleton and shells. After dying they form biogenetic or organo-genic sediments.

Peat, coalPlant residues in moors and moor forests which are deposited under the absence of air and cannot decompose to water and gas. These form fibrous peat which then changes to limnic peat, lignite, brown coal, bituminous coal and anthracite.

2.1.3 Metamorphic rock

e.g. quartzite, marble, lime silicate, slate, phyllite, mica schist, gneissic rock

Metamorphic rock consists of original extrusive igneous or sedimentary rock which were pressed down to deeper depths by tectonic processes, where they were changed to crystalline rock by high overlying strata pressure or by melting.


58

2.2 Description of rock

During the investigation for engineering or mining purposes in rock the following points must be recorded and uniformly described according to DIN 4022, part 2: the drilling engineering data and prop-erties as well as the results of the drill cuttings (drill-ing core, sample core, core piece), the drilled rock by type and colour, the divisional planes by number and formation as well as the depth and position of the encountered water conditions.

Type and condition of the drilled cores and rock material must be described in detail; this includes type of rock, granularity, space factor (dense, porous, cavernous), strength and grain binding, hardness, variability in water, colour, indications to bonding agents, angularity, condition of surfaces and cutting planes.

2.3 Parting plane structure of rock

Apart from its stratigraphical and petrographical characteristic the rock mechanical properties of rock, especially its deformation performance under tension and its permeability, are primarily influenced by its parting plane structure.

The parting plane structure comprises the entity of all discontinuity surfaces of a mountain, these are - the cutting planes resulting from sedimentary processes- the secondary foliation planes caused by tectonic effects- the joint planes resulting from tectonic processes as well as stress differences caused by pressure and temperature, whereby dislocations (para- clases offset to each other) are generated.

The parting planes are described and evaluated by their distance and spatial orientation (direction of strike and dip). Furthermore, the parting planes must be assessed by their condition and the degree of separation (Tab. 16).

Mean distance Designation (in cm) Jointing bedding / foliation Toleranz ± 20% < 1 foliated/schistose 1 – 5 excessively jointed thin-shaly 5 – 10 strongly jointed thick-shaly 10 – 30 jointed thin bedded 30 – 60 slightly jointed thick bedded > 60 compact massive

Tab. 16: Classification of parting plane distances with designation

The joints are described and evaluated by the mini-mum and maximum size of the rock fragments, the joint system (total number of joint planes), the joint width and their extent (direction, length). Shape and size of the rock fragments are determined by the distance of the parting planes: see classification in Fig. 60 (Lit. 12) and Tab. 16 acc. to the code of practice for rock description for road construc-tion (FGSV = German Road And Transportation Research Association).

Classification of rock fragments by L. Müller Fig. 60

In areas close to the surface the structure of the parting planes may be loosened by weathering or construction related stress effects (Tab. 17). This loosening appears e.g. in form of cracks, crevices, widening, rifting. The attributes of loosening can be characterised by distance, degree of separation and gap width of the parting planes.

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59

2.4 Strength and deformation properties of rocks

Fracture strength, tensile strength, bending tensile strength and shearing strength are some of the most important strength values. Parameters for these strength values and some further properties can be found in the appendix A 3.

The single and multi-axis fracture or compressive strength σD increases with the proportion of the par-ticle size and the structural stability of the pressure resistant and non-cleavable minerals. Pore spaces, micro-cracks, weathered mineral aggregates and cleavable minerals reduce the structural stability and the compressive strength accordingly.

The tensile strength σZ characterises the adhesive and cohesive bonding strength between the min-eral aggregates of the rock. It decreases with the coarseness of grains and the above mentioned dis-continuities. ZσZ is approximately 1/10 to 1/20 of the compressive strength σDD.

The shearing strength fτf characterises the frictional and interlocking resistance of the mineral aggre-gates in the rock under shearing stress. It decreases with the proportion of cleavable materials, clay and water. τf is approximately 1/2 to 1/20 . σDD.

The deformation properties of rock depend on its strength and anisotropy: Hard rock with a dense structure behaves like an elastic solid body. A jointed, but massive rock responds mainly plasti-cally under initial loading, but becomes increasingly elastic when repeating the load process several times. Soft rock deforms plastically up to fracture.

The sensitivity to weathering and frost can be inves-tigated on the rock aggregates by water immersion, dry-wet cycles and frost-thawing cycles.

Heaving and swelling performance can be deter-mined by special mineralogical investigations as well as heaving tests, measurements of the heaving and swelling pressure, investigations of the water absorption capacity and the shrink measurement, the extraction and alteration of minerals by water immersion tests.

Designation Characteristic of rock Characteristic of mountain range Non- non-weathered, fresh, no apparent no loosening on separating planes weathered effect of weathering caused by weathering starting of on fresh break plane single partial loosening at the separating planes weathering mineral particles show signs of weathering (magnifying lense), start of mineral transformation and doiscoloration desolidified mineral structure loosened by completely loosened at the parting planes weathering processes, but still interlocked, mostly in connection with mineral transformation, especially with an on parting planes decomposed rock changed by mineral transformation Rock fragments without solid rock properties without the properties of a solid rock material, but still in the rock structure e.g. transformation of feldspar materials to clay materials, from clay shale to clay)

Tab. 17: Weathering level of rock acc. to leaflet (FGSV = German Road And Transportation Research Association)


60

2.5 Suitability of rock (Lit. 11, 23)

2.5.1 Exploitation of rock as filling material

Ripping of rock

The working method (ripping equipment, planning of exploitation, heading direction) depend on the strength and the parting plane structure of the rock to be loosened. As far as possible, the rock shall be ripped fragmentary to a wide graded mixture with favourably shaped stones, to obtain a well compactible filling material; If necessary it must be additionally crushed. Prerequisite for these quality requirements is a narrow parting plane structure with blocky, cubic components.

Pretests are therefore required to determine the optimal direction of ripping, the depth effect of the ripper tooth as well as other conditions, by which the best graded mixture is achieved. The loosening is accomplished by optional equipment on hydraulic excavators, such as ripper teeth, scarifiers, single and multi-tooth rippers, chisels.

The speed of seismic waves is a criterion for the rip-pability of rock. Fig. 61 shows approximate limits of the rippability.

Ripping ability CAT D 9/D 10N in dependence on the seismic wave speed in soil / rock

Fig. 61

Blasting of rock

The blasting of rock requires pretests in order to optimise the line of least resistance and the lateral distance of the boreholes as well as the length of the stemming zone and the ignition sequence in

dependence on the borehole depth. The following blasting methods may be used to obtain almost cubic, fragmentary rock as filling material:

Method I

This method requires the use of highly explosive materials with millisecond igniters or with short-delay detonators (ignition sequence 0.5 or 1.0 s), to break the rock mainly by the detonation pres-sure. Big distances or overcharging of the bore-holes cause shaking of the surrounding area and disturbance to the slope areas.

Method II

The same effect, but with less shaking of the sur-rounding area and less disturbance of the rock for-mation, can be achieved by multi-row blasting using millisecond or short-delay detonators with a small distance between boreholes and medium to low explosive materials.

With this method the small distance between the boreholes results in a good breaking effect despite the buffered detonation waves, because the blast-ing energy is evenly distributed and the rock is uni-formly loosened and broken down.

2.5.2 Rock classes

Classification of rock classes 6 and 7 according to DIN 18300 see T 2, para. 1.2The classification of rock of classes 6 and 7 com-plies with a simple classification into the following two main groups frequently used in practice:

- Soft, weather-sensitive rock of low strength, breaking under mechanical load or crumbling to water- sensitive soil types under the influence of frost, water, air or other weathering processes. These types of rock include most slates, and also carbonate rock such as marl and limestone as well as clastic rock such as sandstone, siltstone and mudstone.- Hard rock, less or non-sensitive to weather influences, the grain size and grain shape of which remains almost unchanged under mechanical

Part 2

61

loads. This type includes most intrusive and extrusive igneous rock and dyke rock, and also meta morphic rocks such as gneiss and mica schist as well as siliceous rock such as quartzite.

Although the soft rock types frequently belong to class 6 and the hard rock types to class 7, the char-acteristics “hard” and “soft” on their own are not suf-ficient for a clear classification of rock with respect to its workability. Petrographic, tectonic and weath-ering dependent characteristics must be addition-ally used as evaluation criteria. These are

- the weathering condition,- the parting plane structure according to type, orientation in space (dip, strike), distance of the parting planes as well as to size and shape of the separated volume parts.

2.5.3 Placement and compaction

Solid rock:

When classifying rock with respect to its suitability and use as embankment material, loading, haul-age, placement and compaction are of importance, besides the loosening which is normally accom-plished by blasting, milling or charring (borrow, precut, tunnel). During this process and when esti-mating the cubatures one must make sure that, after loosening, the rock material is available for placement in a similar condition as the loose soil deposits. Reliable evaluations can, in most cases, only be made during mining in form of an accompa-nying classification.

Solid rocks are rock materials which do not change their properties by weather influences. They are most suitable for rockfill embankments and, with well graded fragmentary components, they may also be used for the filling of higher embankment zones. The conditions are particularly favourable if the rock mixtures consist of well graded fractions with a fines content of less than 15% and a maxi-mum stone size of 150 mm. The stone size of such mixtures shall normally not exceed two third of the lift height that is permitted for compaction (example Fig. 62).

Compacting blasted dolomite using a 19 t single drum roller in layers of 150 cm Fig. 62

Rock material which is too coarse after loosening can be placed by applying the following methods.

- Placement of the rock material in alternating layers with 20 to 30 cm regulating layers consisting of coarse particle material so that the filling is pass- able and compactible without any problems.- Sorting out of blocks with a volume of more than 0.1 m³ (corresponds with a ball diameter of 60 cm) and placement in the toe areas. If such blocks are placed in the inner zones of a dam, cavities may remain which will later cause settlements resulting from the dislocation of these boulders.

If the proportion of rock blocks is so high that sort-ing out is uneconomical, the material may either be broken down at the source of mining by means of auger drills or in a simple mobile crushing plant. During loading, haulage, unloading and distribution


62

of the rock mixture segregation must be avoided or the material must be remixed in special work proc-esses.

Rock with variable strength

Rock with variable strength includes a variety of facies and are characterised by origination related significant differences with respect to their strength and deformation properties, on the one hand with transition to the clay and on the other hand to solid rocks.

Generally valid rules for the placement and com-paction of such rock materials are only possible to a limited extent. Their suitability as embankment material must be examined on the basis of either regionally available experiences or the results of material specific trial compaction.

In Germany the rocks with variable strength are mainly represented by siltstones and mudstones, slates as well as diverse types of sandstone:

Siltstones and mudstones

In the structure of rock mass they are normally characterised by distinct stratification and joint planes, by changes from non-weathered to weath-ered strata with different stratum and bank thick-nesses and by partly regular, partly irregular joint plane structures. Depending on the parting plane structure the weathering horizons may locally differ considerably and reach down to various depths. The filling of the joints consists mainly of water-bearing, highly plastic weathered clays, which, in case of the dip of the layers, form prescored sliding planes.

The more distinct the parting plane structure, the narrower the parting plane distances and the more sand and silt enriched the mudstones become in the transition to the siltstones, the easier the loos-ening in ripping operation will become when using appropriately heavy caterpillars and auger drills. If appropriate ripping equipment is used and the working direction is adapted to the changing dip and strike of the stratum and joint planes, a frag-mented size of the material can be achieved which

is directly suitable for placement. A great differ-ence in the fragment sizes must also be considered because of the substantial differences or changes in parting joint structure, degree of weathering and stratum or bank thickness. In less jointed, non-weathered bedded areas or as a result of loosen-ing up blasting loosened bedrocks of more than 0.1 m³ in volume occur, which require special crush-ing, whereas in extremely jointed areas well graded and well compactible broken material down to the gravel fraction may be found. During excavation in friable weathered areas extreme decay and abra-sion may occur and lead to high proportions of sand and fines. In case of a segregationj of these grain fractions gap graded fractions can be expected.

In loosened condition for both the still non-weath-ered as well as the already weathered siltstone and mudstone it must be considered that a permanent degradation of durability will occur. The strengths of the quarry-stones will extremely drop by the disso-lution of the original structure of rock mass and the resulting destressing of the rock as well as by the increase of possible weather influences caused by water, swelling, frost and drying. By experience the highest loss of strength occurs after several drying/wetting cycles and during frost/thawing cycles, even in rock initially showing only slight changes during immersion in water.

Due to the properties described hereunder it must be considered that the placement and compaction of mudstone and siltstone remains very sensitive to weather and frost. The placement should therefore take place under dry weather conditions, whereby the material should be directly transported to the placement location without intermediate stockpiling and that it should be compacted in lifts as thin as possible. In most cases placement and compaction work cannot be continued during frost and longer precipitation periods. If the rock material arrives at the placement location not completely dry no water should be added, since the admission of too much water may considerably impair the compac-tion properties and the surfaces will become slip-pery and soaked, so that passing of vehicles may be impossible. After resuming work it may first be necessary to remove the top, softest layer or to reduce the water content by application of special

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measures, in order to achieve a particularly good interlocking effect with the subsequently following lift. On the other hand the dry placement holds the risk of an extremely increasing compaction resist-ance and that the compacted layer contains too many and large air voids. The drier the mudstone used for filling, the higher the required compaction effort; i.e. heaviest compaction equipment, low lift heights and a high number of compaction passes are required.

Due to the highly weather dependent placement and compaction properties and because of the high compaction effort the variably solid siltstone and mudstone materials are only to a limited extent suit-able for embankment construction. Normally long-term subsequent settlements must be expected which, however, can be minimised by intensive compaction to remaining pore porportions of less then 10%.

Slates

In the structure of rock mass the various slates possess a more or less distinct platy foliation with mostly slight, but occasional bigger distances between the foliation planes. They are highly varia-ble solid rocks which can weather, soak and decay. These processes may also continue even in com-pacted condition.

With an optimum water content during placement and with a protection against seepage water slates are mostly suitable for embankment construction, but must be compacted to a very low air void con-tent, i.e. with high energy, which is particularly dif-ficult because of the platy lumpiness.

Sandstone and calcareous sandstone

These rocks can be found alternately fine or coarse in their structure, but also dense to highly porous. Even though they are solid rocks they still have a relatively low compressive strength, so that exces-sive particle crushing and accumulation of fines will occur during placement and compaction. As far as these contain argillo-marlaceous components, they possess weather sensitive properties and perform very sensitive to water and weather during place-ment and compaction in rain periods and also to frost during frost periods. They are generally suit-able as embankment material; under consideration of the required lumpiness and gradation they can be used in all embankment areas if they are com-pacted to a low air void content (example Fig. 63).

Compacting and subsequent crushing of sandstoneusing a 25 t single drum roller with special drumon 60 cm layers Fig. 63


64

- construction site conditions (confined or spa- cious working areas, accessibility, obstructions caused by site operations).

For the variety of applications table 18 and figures 64 and 65 provide initial decision aids in form of an overview.

3. Application and performance of the BOMAG-compaction technology (Application and performance Lit. 23, 24 to 28, quality assurance Lit. 17 to 23)

3.1 Applications

The productive capacity of the vast variety of BOMAG compaction machines ranging from hand-guided light equipment up to heavy self-propelled single drum rollers and heavy-weight towed rollers covers a wide range of applications with all types of use.

When deciding on the suitable compaction machine the following factors must be taken into considera-tion:

- soil and rock specific properties- quality requirements for the execution (degree of compaction, uniformity, evenness),- economical performance,- machine costs

Machine type/ Vibratory Vibratory Single wheel Double Tandem Combin. Single Towed application tamper plates vibratory vibratory rollers rollers drum rollers (soil compaction) rollers rollers rollers Road construction O X O O X X Railway construction O X X Airport construction X X Hydr. engineering/ landfill site constr. O O X X Side and cycle paths Entrances to yards and garages X X X O O O Parking lots and industrial yards O X O O X Playgrounds and sports facilities X O X O O X Trenches O X O X X O nar. trenches <50 cm X O x = well suitable, O = suitable

Tab. 18: Fields of application for vibratory compaction equipment

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Application of soil compaction equipment Fig. 64

Typical applications for light equipment Fig. 65


66

In order to optimise the compaction work it is nec-essary to observe a number of soil specific and equipment related factors as well as factors deter-mined by site conditions when choosing the com-paction machines for a certain application. Table 19 shows an overview.

3.2 Calculation of compaction output

For the economical use of equipment it is important to know the compaction capacity of the machine.

The following formula is used to calculate the area capacity of a compactor:

b . v . 1000 QA = f . [ m 2 /h ] z

Where: actual outputf = Efficiency factor = basic output

b = Working width of compactor in mv = Rolling speed of compactor in km/hz = Number of passes

In order to calculate the actual output, the theoreti-cal basic output must be adjusted by the efficiency factor f. The efficiency factor takes into account all significant influences on machine performance resulting from the condition of the machine, oper-ation and site conditions, site management and weather conditions. In earthwork an efficiency factor of f = 0.75 is normally applied.

The volumetric output of a compactor is calculated for m³/h in earthwork or in t/h for mixtures.

b . v . h . 1000 QV = f . [ m 3 /h ] z

or

b . v . h . 1000 QV = f . ρ [ t /h ] z

Soil material Machine Placem. conditions

Coarse particle soils Type of roller Condition of

• Shape and rough- • static roller subgrade

ness of particles • pneumatic tired roller • high stiffness

• Particle compo- • vibratory roller • low stiffness

sition and grading

• Water content Design features Layer thickness

• weight • thick layer

Fine particle soils • weight distribution • thin layer

• Particle compo- • vibrating mass

sition

• Plasticity • Geometry and Number of passes

• Water content number of drums

or tires Water situation

Mixed particle soils • water content too

• Particle compo- Application values high

sition • frequency • water content too

• Mixing ratio of • amplitude low

fine and coarse • tire inflation pressure

particles • rolling speed Weather conditions

• Plasticity of the

fine particle fraction Rolling technique

• Water content of the

fine particle fraction

Rock

• Strength of rock

• Particle size and

particle roughness

• Particle composition

and grading

Tab. 19: Factors influencing compaction

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η1 = Repair and maintenance ( 0.95 - 0.75 )η2 = Operational disturbances such as breaks, site traffic ( 0.85 - 0.70 )η3 = Organisational influences on the construction site ( 0.95 - 0.80 )

Compaction operations are generally performed in two alternative exemplary ways (Fig. 66 and 67):

a) Strip-by-strip operation Each strip is compacted as specified before the compactor changes to the next strip. The strips are either overlapped by half the drum width, or successively compacted with a working distance of 10 to 30 cm. This operation enables the operator to count the number of passes, to monitor his work without leaving any areas uncompacted.


Completion of compaction work by tracks Fig. 66

Where:

h = Lift height of the compacted material in m

ρ = Density of the compacted soil or rock mixture in t/m3

For the calculation of output in earthwork the lift height is of particular importance. The optimal and permissible lift height depends substantially on the soil type. Under normal conditions the compaction requirements are met after four to eight passes; see also Tab. 20 to 23.

Example

Construction task: Compaction of a gravel-sand lift, lift height ( compacted ) h = 0.50m

Compactor: 12t single drum roller BW 213 D-3 - Working width b = 2.13m - Rolling speed v = 3.0 km/h

Calculation of output: Efficiency factor f = 0.75 Number of passes z = 6

Areal output

2.13 . 3.0 . 1000QA = 0.75 . = 799 m2/h 6

Volumetric output

2.13 . 3.0 . 0.50 . 1000QV = 0.75 . = 399 m3/h 6

A site specific consideration of the performance reducing factors is also possible by using a total influence factor φges instead of the efficiency factor f:

ηges = η1 • η2 • η3

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b) Overlapping changing operation After each first or second pass the compactor changes over to the next strip. This procedure of strip changing is continued, until the entire area is sufficiently compacted. This operation holds the risk that the outer strips are not sufficiently covered and the required number of passes is not correctly met, especially after breaks and long working times.

3.3 Trial compaction

Trial compactions are executed if no sufficient expe-riences are available before the start of construction work. They are used for various purposes, such as:

- Investigation of the placement and compaction water content of soil, rock and special construction materials- Optimisation of working processes and the use of equipment- Examination of the inherent deformation of fillings and subsoil deformation under applied earth loads.

Depending on the purpose a differentiation must therefore be made of whether the trial compaction is part of the specified execution of work or an inde-pendent specific work used as help for planning, design and tender or as an assurance for construc-tion method chosen by the contractor. In case of the suitability investigation for specific earthwork materi-als it is a suitability test in accordance with the regu-lations for earth construction. If they are performed as a measure to optimise work, they are quality con-trol tests of the contractor. If used as planning aid

Trial field with three successive test units and different lift heights and a specified number of passes Fig. 68

Top view

Cross section

Longitudinal section

LR LALP LA LR LR

LA LP LA LALP LA

LR

Bges

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Areal processing with offsetting of tracksafter two passes Fig. 67

69

they are part of the ground and soil exploration and, as an early measure, should be performed in due time before invitation to the tender.

Trial compactions also become necessary for research and development activities, if new con-struction materials or methods are to be tested.

The trial compactions, which become necessary at the start of compaction work or when changing the compaction method, are part of the contractually required works. This applies also for placement work necessary for trial compaction. The trial compaction, that can be executed either on a filling or on the base plane of a cut, is primarily used for the verification of the work method chosen by the contractor with respect to the quality criteria required by the contract (e.g. degree of compaction, deformation modulus), or for comparative calibration of these criteria with the results obtained by other testing and measuring meth-ods. These trial compactions enable the contactor to

optimise his execution of work. Fig. 68 and 69 in con-nection with the following recommendations for the minimum dimensions of the test units show examples for the preparation of test fields for trial compaction:

Length

Lges = 2 LR + LA +LP

= Overall length > 15m

LR = 10 D = ramp length (m) (not needed when preparing inside the construction field)LA = Start and run-out section = Length of compactor (m)

LP = 4a + 3p = Length of trial section (m) D = Thickness of compacted lift (m) a = Distance to and between trial sections (m) p = Length of trial section (m)

Trial field with one test unit and one lift height and a specified number of passes Fig. 69

Cross section

Top view

Longitudinal section

Trial section

Trial field

Trial locations

LRLA LP

Lges

LA LR

a p a p a p a

Bges

b BG BPBG

b

bBG

BP

BG

b


70

Width

Bges = 3 BG - 2 Ü + 2 b = 2 BG + BP + 2 b = Overall width (m) > 5m

BG = Width of compactor (m)

Ü = 0,1 BG = Overlapping of strips (m)

BP = BG - 2 Ü = Width of trial section (m)

D = Thickness of compacted lift (m)

b = D (m) = Safety distance

In order to be able to evaluate the achieved com-paction, the degree of compaction DPr or the den-sity pd shall be detected over the entire thickness of the lift. Apart from density tests other suitable tests should also be comparatively be performed to enable a determination and evaluation of the inter-relationship between the respective results already at the time of the trial compaction.

3.4 Placement and compaction water content

s. information in T 2, para 1.3.2 and 2.5.3Compaction of the fine, coarse and mixed particle soils shall take place at the optimum water content wPr, approximately within the limits from + 1% to - 2%, if this is possible.

The lower the water content, the more difficult the processing of soils which are too dry for com-paction. In most cases theses soils need to be moistened, although this is time consuming and expensive. The following measures are possible:- artificial sprinkling during loosening at the source,- addition of water in the transport vehicles by means of pressure sprinkler systems,- addition of water at the placement location by means of sprinkler truck, if necessary with water pump.

The addition of water only makes sense if it is applied in a controlled manner and the soil is uni-formly moistened. In case of clayey soils a uniform moistening cannot be achieved without additional milling and mixing processes.

Soils with a too high water content must not be placed and layers subsequently soaked to deeper depths must not simply be covered. A too high water content reduces the achievable dry densities and does not allow for an optimal compaction. Under certain soil conditions vibratory compaction has the effect of “pumping” free, excessive water to the sur-face, thereby soaking the zone close to the surface even more.

The water content can be reduced by aeration, drying, milling or adding of water-binding sub-stances (Fig. 70).

Drying of a soil layer by sunshine and wind may take quite a long time (several days up to weeks) until compaction can be continued. Difficulties caused by rainy weather can be minimized by auxiliary con-struction measures:

- Installation of drainage gutters or ring trenches around the placement location to catch water flowing in from outside,

Compaction recommendation for soils withhigh water content Fig. 70

Pumpeffekt

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- Arrangement of the surface slope at the placement location in such a way, that water is dis charged to the outside.- Application of milling machines and graders to aerate the soil layer, to level vehicle tracks and to remove water deposits,- Placement of thin, uniform lifts which are immediately compacted with sufficient results,- Before longer breaks temporary overfilling of the placed layer with extreme slopes to both sides,- Mixing in of quicklime as a measure to reduce the water content in the soil (Fig. 71).

The placement of thin layers in combination with the use of padfoot rollers for compaction in case of a high water content in the soil layer or under unfavourable weather conditions may be suitable for a continuation of compaction work over a longer period of time. However, this requires that the earthwork operation can be changed to the place-ment of thin layers and that the soil is suitable for compaction with padfoot rollers. This placement method requires more time, especially since addi-tional passes with heavy smooth drum rollers are required to seal the surface.

Another counteracting measure in case of a too high water content is the change to the “sandwich” method, .i.e. placement of alternating layers of gravel, sand or rock.

For special placement situations, e.g. sealing layers consisting of plastic clay, a relatively high water

Improving the compaction properties of a fine particle soil by mixing in lime Fig. 71

content is required to achieve a water tightness as high as possible. In such cases a static compaction of a highly reduced lift height with smooth drum roll-ers without vibration may lead to the best results.

When compacting solid rock material an addition of water is normally not required. In most cases water sensitive rock material of variable strength acquires unfavourable placement and compaction properties when water is added or absorbed. With very dry rock material slight wetting of the surface may have a positive effect on the compactibility (e.g. mud-stone).


72

3.5 General equipment and soil specific recommendations

As described in T 1 „Basic principle of vibratory compaction“, certain machine parameters have a substantial influence on the optimisation of compac-tion. These important parameters of the vibratory

Recommendations for vibratory rollers for average lift heights Fig. 72

Data on output per hour and average compaction depth or compaction lift height can be estimated on the basis of the reference values in tables 20 to 23. By general experience, self-propelled compac-tors have a higher mobility and are more flexible in

compactors include the static linear load, ampli-tude, vibrating mass, frequency and rolling speed. The following data can generally be valid as guide-lines for commonly used lift heights:

operation than hand-guided machines. They there-fore have a higher efficiency and cause less stress for the machine operator.

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Lift height compacted in (m) Machine Operating weight Rock Gravel, sand Mixed soil Silt, clay

kg kg 50 - 60 - • 0.30 - 0.40 • 0.20 - 0.25 0.15 - 0.20 70 - 80 - • 0.30 - 0.40 • 0.25 - 0.30 0.20 - 0.25

40 - 100 - • 0.10 - 0.20 • 0.10 - 0.20 - 120 - 250 - • 0.20 - 0.30 • 0.20 - 0.30 0.10 - 0.15 300 - 450 - • 0.30 - 0.40 • 0.25 - 0.35 0.15 - 0.20 600 - 800 0.30 - 0.50 • 0.50 - 0.70 • 0.40 - 0.50 0.20 - 0.25

600 - 800 - • 0.20 - 0.25 • 0.20 - 0.25 0.10 - 0.15 900 - 1200 - • 0.20 - 0.30 • 0.20 - 0.25 0.10 - 0.15

1500 - 1600 - 0,25 - 0,30 • 0,25 - 0,30 • 0,20 - 0,25

• Machine particularly suitable for this type of soil Tab. 20: Reference values for compactible lift heights

Lift height compacted in (m) Machine Operating weight Rock Gravel, sand Mixed soil Silt, clay

t kg 1.5 - 2.5 - • 0.20 - 0.30 • 0.20 - 0.25 0.10 - 0.15 3.0 - 4.5 - • 0.25 - 0.30 • 0.20 - 0.25 0.15 - 0.20 7 - 9 - • 0.30 - 0.40 • 0.20 - 0.30 0.15 - 0.20 10 - 12 - • 0.30 - 0.50 • 0.25 - 0.40 0.15 - 0.20

2 - 3 - • 0.20 - 0.35 • 0.20 - 0.35 0.15 - 0.20 6 - 8 0.30 - 0.50 • 0.30 - 0.50 • 0.25 - 0.35 • 0.15 - 0.20 9 - 12 0.50 - 0.80 • 0.50 - 0.60 • 0.30 - 0.45 • 0.20 - 0.25 13 - 16 • 0.80 - 1.20 • 0.50 - 0.80 • 0.40 - 0.60 • 0.20 - 0.35 19 - 25 • 1.00 - 2.00 • 0.80 - 1.50 • 0.60 - 1.00 • 0.30 - 0.50

6 - 7 • 0.50 - 0.80 • 0.40 - 0.60 • 0.30 - 0.45 • 0.20 - 0.30

• Machine particularly suitable for this type of soil Tab. 21: Reference values for compactible lift heights


74

Compaction output (m3/h) Machine Operating weight Rock Gravel, sand Mixed soil Silt, clay

kg kg 50 - 60 - 8 -15 6 - 12 5 - 10 70 - 80 - 8 - 17 6 - 14 6 - 12

40 - 100 - 5 - 15 5 - 15 - 120 - 250 - 15 - 25 15 - 25 8 - 14 300 - 450 - 25 - 60 20 - 50 10 - 25 600 - 800 60 - 100 90 - 120 60 - 100 25 - 50

600 - 800 - 30 - 40 30 - 50 15 - 25 900 - 1200 - 40 - 60 40 - 50 20 - 30

1500 - 1600 - 40 - 60 40 - 60 30 - 50

Tab. 22: Practical output of hand guided compaction equipment in earthwork

Compaction output (m3/h) Machine Operating weight Rock Gravel, sand Mixed soil Silt, clay

t kg 1,5 - 2,5 - 50 - 150 50 - 120 30 - 70 3,0 - 4,5 - 70 - 200 60 - 150 40 - 90 7 - 9 - 120 - 350 100 - 250 80 - 150 10 - 12 - 200 - 500 150 - 400 100 - 200

2 - 3 - 60 - 180 60 - 180 40 - 100 6 - 8 200 - 500 150 - 400 100 - 350 70 - 200 9 - 12 400 - 900 250 - 600 250 - 500 150 - 300 13 - 16 500 - 1400 350 - 1000 300 - 800 200 - 500 19 - 25 900 - 2200 600 - 1600 500 - 1200 250 - 800

6 - 7 300 - 600 200 - 400 150 - 250 100 - 200

Tab. 23: Practical output of compaction equipment in earthwork

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If a high compaction is to be achieved in the short-est possible time, the main object will be to start the work with high compaction energy or maximum amplitude until jumping or beating occurs, then to perform the following passes with a lower energy transfer or low amplitude, finally, if the machine shows a repercussion reaction, followed by an solely static compaction without vibration. With this method the intention is to compact the deep area of the layer first and subsequently the area near the surface with a lower energy.

Vice-versa, if a machine works with a low compac-tion energy and a high number of passes first, it may happen that near the surface the layer is ini-tially compacted very intensively, but is loosened or even damaged when high energy is subsequently applied.

In this case the directed vibrator system VARIO-CONTROL with controlled amplitude developed by BOMAG is a great help (see T 1, para. 2.1.4), because the single drum rollers with VARIOCON-TROL transfer the maximum possible compaction energy at any time, without the drum changing to the unfavourable jump operation or causing over-compaction.

The compaction of rockfill material requires heavy machines with a static linear load of at least 30 kg/cm. Oversize lift heights and cohesive soils, especially those with highly plastic properties, also call for heavy machines, as far as this is permitted by the passability and load bearing capacity. With normal soil conditions and lift heights all other soil tasks can be accomplished with less heavy equip-ment.

Overcompaction of a soil layer occurs when a dense bedding is already reached and the introduction of compaction energy is still continued. In this case loosening, segregation, particle destruction and an increase of the fine particle fraction may especially occur in the layer areas near the surface.

The reactive forces effecting the machine in case of overcompaction cause damage and expensive repairs. If the overcompaction causes jumping and repercussion of a roller, the vibrator system will experience a hard impact during one revolution of the eccentric mass and lose ground contact during the next revolution.

This continuously changing vibration with impact and loss of ground contact is extremely stressful for the machine.

Even compactors with impact vibration, such as tampers, may be damaged when working on an overcompacted soil layer, because the normally dimensioned impact vibration changes from a har-monically controlled to a non-uniform operation.

If there is a risk that a soil layer may be overcom-pacted, the compaction energy must be reduced as exemplary shown in Fig. 73:

3.6 Special machine specific compaction effects

3.6.1 Static smooth drum rollers

The compaction effect of these rollers improves with increasing static load. The required number of passes drops with increasing linear load. At a cer-tain linear load the compaction effect and the depth effect rises with the increase of the water content, but only within the optimal range. With a high linear load and a small lift height a good compaction effect can even be achieved with a water content below the optimal level. On mixtures of gravel and sand as well as gravel-sand-silt mixtures the depth effect is higher than on soils consisting of silt and clay.

Avoidance of overcompaction Fig. 73


76

3.6.2 Pneumatic-tired rollers

The compaction effect of pneumatic-tired rollers improves with increasing wheel load or tire contact pressure. The required number of passes drops with increasing contact pressure, whereby this influ-ence is reduced as the water content increases. The compaction depth also rises with the contact pressure or the wheel load, the contact pressure is mainly effective in the upper zone and the wheel load in the lower zone. The influence of the load has a greater effect on cohesive soils than on non-cohesive soils, because the coarse granular soils are loosened at the surface by the shearing stress applied by the rolling tires.

3.6.3 Smooth drum vibratory rollers

On all types of soil the compaction effect of vibratory rollers is substantially influenced by the dynamic characteristics of the vibrator system, the linear load of the respective roller type and the soil spe-cific properties. Due to the combined effect of vibra-tion and linear load a considerably lower number of passes is required to achieve a certain compaction effect than with the statically working smooth drum rollers. The influence of the linear load on the com-paction depth becomes apparent by the fact that heavy rollers generally have a deeper effect on any soil than light rollers, but that the depth effect achieved with any roller is best within the range of the optimal water content. The depth effect of compaction increases with the number of passes. On gravel-sand-silt-mixtures the compaction nor-mally reaches deeper than on cohesive fine particle soils.

Apart from this it is generally found that the light small rollers become ineffective when compacting fine particle soils with an increasing proportion of clay and a distinct plasticity, even with a very high number of passes.

An increasing rolling speed requires a higher number of passes, similar to the smooth drum roller without vibration, whereby also here this is influ-enced by lift height, operating weight of roller and water content

The water content of the soil has a tremendous influence on the compaction effect of vibratory roll-ers, however, with differences depending on the linear load: The light rollers require more water for an optimal compaction, whereas the water require-ments drops with increasing linear load when using heavy rollers (over 10 kg / cm). The influence of the linear load reduces with increasing water content of the soil.

The size of the vibrator’s centrifugal force has a comparatively minor effect. The vibration frequency influences the compaction effect differently, depend-ing on soil type and initial bedding density.

During the compaction of coarse and mixed parti-cle soils favourable compaction effects arise in the frequency range between 25 and 35 Hz, whereby the required number of passes drops with increas-ing frequency. For fine particle plastic soils no clear statement on the influence of the frequency can be made.

3.6.4 Padfoot rollers with and without vibration

Conventional single drum rollers with padfoot drum in the weight range from 6 to 25 t are used for the compaction of cohesive soils, stony mixed soils and solid rock of variable strength.

They have proved worthwhile because of their appli-cational versatility and their compaction perform-ance. The drums are normally fitted with 100 mm trapezoidal padfoot elements (studs) with flat side faces and scrapers for cleaning. In connection with the vibration these studs produce a kneading and pushing effect, which leads to the reduction of the air void volume and to a pulverisation of lumps and rock fragments. Due to the shape of the padfeet the contact surface increases with the penetration depth. The compaction effect adapts to the stiff-ness of the soil to be compacted via the penetration depth of the studs.

The compaction effect depends substantially on the areal pressure of the ground contact area. Foot shape and covering rate of the studs on the drum shell have a tremendous effect. This effect is

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enforced by the increase of padfoot pressure, the increase of the clay proportion and the reduction of the water content in the soil.

On clayey soils these padfoot rollers compact most effectively at water contents below the optimum, whereby this influence of the water content dimin-ishes with increasing silt and sand fractions in the soil. The compaction effect increases strongly with the number of passes, but also in this case this influence is reduced by a rising water content.

The number of required passes is also influenced by the degree of coverage of the padfoot elements. The more clayey and less moist the soil, the higher the compaction that can be achieved with increas-ing padfoot pressure. Compaction is even possible at a high water content, as long as the padfoot ele-ments have a kneading effect and do not sink in completely.

The surface structure that forms under the roller passes changes strongly with the water content. The thickness of the loose soil ripped up by the profile of the drum is reduced with dropping water content, whereby small or tapered padfeet gener-ally have a higher loosening effect than large area padfeet. Raising the rolling speed results in a sub-linear increase in the number of rolled passes.

3.6.5 Single drum rollers with special padfoot drums

Extensive investigations of BOMAG about the effect of padfoot rollers aimed at higher compaction per-formance on cohesive and stony soils as well as high impact and crushing effects when used on rockfill. This resulted in three special padfoot drums which are already successfully used (T 1 para. 3.6 and Fig. 36).

(1) Rollers with pyramid teeth

Compared with conventional padfoot drums, drums with pyramid teeth are characterised by higher teeth, considerably smaller tip areas and steeper tooth flanks (Fig. 74). Due to their high specific pressure pyramid teeth penetrate deeper into the ground and achieve a more intensive kneading

and compaction of the soil. An additional benefit is the better self-cleaning effect between the teeth on cohesive soils. Clogging of the drums, which is disadvantageous for the compaction effect, is avoided.

(2) Rollers with triangular teeth

For the crushing of hard and brittle pieces of rock BOMAG equipped a 25 t single drum vibratory roller with triangular teeth (Fig. 75). When using single drum rollers with vibration on coarse, solid rockfill the tips of the triangles produce such high pressure and splitting forces, that the desired crushing and edge fracturing of the coarse particles and therefore intensive com-paction of the packing bed is achieved with a consid-erable reduction of air voids. In order to withstand the excessive loads acting on the triangular teeth, their tips are made of a wear resistant material.

Improving the compaction output on boulder clay using a 25 t single drum roller with pyramid teeth Fig. 74

Enhancing the crushing effect of a vibratory roller on quartzite sandstone using a specialpadfoot drum (triangular teeth) Fig. 75


78

(3) Rollers with triangular teeth and cutters in between

For a further improvement of the crushing effect a 25 t roller was developed with triangular teeth and cutters in between (Fig. 76). Stones and blocks are split by the triangular teeth and subsequently crushed by the cutters. At the same time, the cut-ters prevent jamming of crushed material between the teeth.

With the use of special padfoot rollers the highly expensive crushing, screening and manual sorting of large blocks is no longer necessary. The rollers are able to crush and effectively compact lami-nated fragments of mudstone and siltstone as well as lumps of quartzitic sandstone of up to 500mm in size.

3.7 Compaction of marginal zones (slopes, embankment shoulder)

Thorough compaction of slopes, embankment shoulders and other marginal zones is essential for the avoidance of erosion damage as well as damage to slopes and carriageways; Fig. 77.

For compaction of marginal zones of bank fillings light and medium-weight compactors are most suit-able. For method d) in Fig. 77 special slope rollers with the engine at the rear should be used.

Method b) in Fig. 77 is suitable for embankments if the temporarily existing surplus profile is permis-sible and the required surplus masses are included in the balanced cut and fill without additional costs.

Improving the crushing effect of a vibratory roller on quartzite sandstone usinga special padfoot drum (triangular teeth) Fig. 76

Various methods for thorough compaction of slopes and embankment areas Fig. 77

+ 2m-

1

a) Low lift heigt in the embankment area

b) Temporary excessive profile without a change in lift heigt

c) Variation to b)

d) Compaction on the slope

Bild: Verschiedene Verfahren zur sorgfältigenVerdichtung von Böschungsbereichen

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3.8 Compaction of layers on an elastic base

The compaction of multi-layer systems consisting of relatively thin layers on an elastic base, depends on the stiffness condition of the adjacent layers. Prob-lems of this kind are e.g. bearing, filter and sealing layers. The energy introduced during compaction causes a reaction on the particle skeleton from the base, which increases with the stiffness of the base (bearing effect, rigid fixing). In the opposite case the energy is discharged into the base without any compaction effect.

As far as such multi-layer systems are compacted with vibration energy, the resonance range of the entire system as well as the optimal amplitude of the vibratory compactor must be determined by means of trial compactions; general recommenda-tions are:

- machines with low amplitude and high frequency, if the base is of sufficient stiffness and shall not be compacted- machines with high amplitude and medium frequency, if the base shall first also be compacted - VARIOCONTROL machine with self controlling amplitude

In practice an optimal compaction can very often be achieved by combining static and dynamic passes: the first passes with vibration, the final pass without vibration, if necessary an intermediate pass with a pneumatic-tired roller.


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81

1. Asphalt pavements in highway and transportation engineering

Asphalt technology is used for pavements of high-ways and urban roads, for junctions and inter-changes, for bus and rail tracks, for multi-purpose traffic lanes, hard shoulders and median strips, cycle paths and footways, for traffic lanes in service areas, etc.

Pavements of traffic areas are built in form of asphalt surface courses, binder courses and base courses, to ensure high durability against stresses caused by traffic and weathering. The typical structure of asphalt pavements and their functional properties are shown in Fig.78. The design and execution of highway and transportation areas is based on engineering requirements concerning load bearing capacity, stiff-ness against permanent deformation, frost resistance and eveness and the required profile of the pave-ment. Besides the pavement the highway construc-tion also comprises the subgrade and the subbase influenced by static and dynamic traffic loads. This multi-layer system is stressed by load, time and tem-perature dependent shearing and bending forces and deformed in dependence of the stiffness of effective layers.

The carriageway pavement must be designed and built for safe riding traffic under any load condition, whereby its stability shall not be at risk at any time. This design goal demands a constructive interaction of all effective layers and a low and uniform level of defor-mation. According to this principle the layers must - have load distributing properties complying with the different possible types of loads- be able to mutually compensate overloads.

These performance requirements depend on the stiff-ness of the system, which in turn is depending on the strength and deformation characteristics of the layers as well as the layer thicknesses including the thick-ness ratio of successive layers. The principle of the constructive interaction is met when the stiffness pro-perties of the individual layers are adpated to each other in a way that the system stiffness increases from the bottom upwards according to the course of stres-ses.

The stiffness of the system changes because of the permanent mechanical load applied by traffic in com-bination with the local conditions or the seasonal cli-matic cycle. Particularly critical conditions may arise - during winter, when frost related non-uniform heaves occur or the stiffness of the sub-layers drops during thawing intervals.- during summer, when warping stresses develop and the stiffness of the visco-elastoplastic deformable ashalt layers is reduced by high temperatures.

The task of design arises primarily as a deformation problem and is based on technical criteria, which can be derived from the rideability of the pavement; these are- the permissible deformation and - the required stability (load bearing capacity) of all layers contributing to the load distribution and influenced by local conditions.

Pavements shall therefore be designed and built accor-ding to the following two examples: a) Construction in accordance with the required stiffness or the permissible deformation of the layers with the objective, to maintain such deformations at the lowest possible and most uniform level b) Construction of the required load bearing capacity of the layers including the subbase with the goal of maintaining any compression, shearing and bending stresses at such a low level, that deformation caused by tension and shearing will not cause cracking.

This design is accomplished by application of theoreti-cal methods of elasticity or plasticity, the applicational limits of which are described in Lit. 30. Some of the soil parameters, which form the foundation of this method, are mentioned in Lit. 23.

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In the practice of highway engineering the described principles are simplified to a great extent, by stan-dardising both structure and layer thickness of widely approved construction methods, in dependence on simple assumptions concerning the magnitude of traf-fic loads (Fig. 79). The German regulations for the standardisation of pavements for traffic areas (RSTO-86/89) differentiate the pavements for the various types of roads and highways according to traf-fic load dependent classes (Fig. 79). The traffic load index (VB) is mathematically determined on the basis of the average daily heavy vehicle traffic and factors for the forecasted increase in traffic, the number and width of the traffic lanes as well as factors for the gra-dients and higher axle loads.

The types of asphalt pavements are designated accor-ding to the type of asphalt surfacing and differentiated according to table 24. Asphalt surf. Type of asphalt (normal types) Asphalt concrete (hot mix) Stone mastic asphalt Gussasphalt Asphalt mastic Combined surface-base-course Asphalt concrete (w. cutback bit.) Asphalt veneer coats (special types) Cold thin surface courses Hot thin surface courses Porous asphalt Rolled gussasphalt

Tab. 24 Types of asphalt surfacings

Examples for asphalt pavements in highway engineering acc. to RSTO-86/89 Fig. 79

Structure and functional properties of asphalt pavements Fig. 78

Construction class SV I II III IV V VI Traftic load index (VB) > 3200 1800 - 3200 900 - 1800 300 - 900 60 - 300 10 - 60 < 10 Thickn. of frost res. pavement 60 70 80 90 50 60 70 80 50 60 70 80 50 60 70 80 50 60 70 80 40 50 60 70 40 50 60 70 Asphalt base course on frost blanket layer surface course Binder course Asphalt base course Frost blanket layer

Thickn. of frost blanket layer 26 36 46 56 - 30 40 50 - 34 44 54 28 38 48 58 32 42 52 62 26 36 46 56 30 40 50 60

subgrade

pavement

subbase/subsoil

even, grip, denseAsphalt surface course wear resistantAsphalt binder course

Frost blanket layer

shear. res.

stable

Asphalt base course

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Asphalt surfacings normally consist of an asphalt surface course and an asphalt binder course. Asphalt surface courses require special traffic related properties, such as grip, evenness, resistance against polishing, abrasion, moisture, de-icing salt and it must also provide sufficient sealing for the lower courses against surface water. The binder courses are located between the asphalt surface course and the base course. They enhance the stability and durability of the asphalt surface course and of the complete asphalt pavement. Pavements which are only subjected to low traffic loads do not require a binder course or the asphalt surface course can be replaced by a so-called surface protection layer (T 3, para. 3.4).

Asphalt surface courses are normally applied with a thickness of at least 4 cm. The standard thicknesses of binder and base courses vary strongly in dependence on construction class, overall type of construction of the pavement and the composition of the mixture: Standard thicknesses of binder courses at least 4-8 cm, of base courses 8-22 cm. For further information on layer thickness see T 3, para. 3.3.

With exception of gussasphalts and the surface treat-ments, all other types of asphalt are so-called rolled asphalts, the application of which requires compaction by static and/or vibratory compaction energy (see T 3, para.3 to 5). For the air void content in compacted con-dition minimum values in Vol.% of 6-7 apply for asphalt surface courses, 3-7 for binder courses and 4-14 for base courses. The degree of compaction (see T 3, para. 4.1) is at least 96 and 97% respectively.

Traffic load (type and amount of traffic) as well as the climatic and local conditions must be taken into consideration when selecting the components and the cdesigning of the mixture. The mixture must be pro-portioned in such a way, that it possesses the quality required for the intended use. The substantial values for the execution of the work must be specified by the contractor on the basis of the mix design. The appli-caple limit values and tolerances for the execution of the work contain work related deviations as well as tolerances in sampling and testing.

The requirements on the characteristics of the various types and grades of mixtures as well as for the construction of asphalt pavements are specified in German General and Additional Technical Con-tractual Conditions and Guidelines (ATV / ZTV-Stb). Important regulations see appendix A4.

2. Bitumen and bituminous binders (Lit. 32)

2.1 Types and manufacturing

Bituminous binders as used for highway and trans-portation engineering mainly origin from the crude oil refining. The materials are classified according to the following groups:(1)bitumens as mixtures of high-molecular hydrocarbons, characterised as dark substances with highly viscous to semi-hard adhesive properties under normal temperatures,(2) the additive modified bitumens, suitable for hot, warm or coliquid processing after adding oil (light, liquid hydrocarbons),(3) bitumen containing binders in form of bitumen solutions, bitumen emulsions and polymer modified bitumes.

Further terminological differentiations relate to the dif-ferent manufacturing methods and areas of applica-tion (Fig. 80).

Zur Herstellung der Bitumen werden die in den Erdölen enthaltenen Bitumenanteile von den leichte-ren Bestandteilen getrennt, wofür verschiedene Trenn-prozeduren zur Verfügung stehen:

For the manufacturing of bitumen the bitumen compo-nents contained in the crude oil are separated from the lighter components. This is accomplished by one of several possible separating procedures:

(1) distillation with the help of steam and vacuum as well as in connection with oxidation, (2) precipitation using special precipitants (e.g. liquified propane), (3)extraction using special extraction agents (e.g. phe- nolic and propanoic mixtures).

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84

Besides the type and origin of the crude oils these manufacturing methods have a significant influence on the properties of the bitumen. One very important differentiation characteristic of the bitumen grade is the hardness. During the distillation process the hard-ness of the bitumen grades can be controlled by the selection of the distillation conditions: The higher the distillation temperature and the lower the throughput rate of crude oil per unit of time, the more heavy oils are separated by distillation and the harder the recovered bitumen. Very hard bitumen (vacuum bitu-men) can be recovered using a higher vacuum. Bitu-men grades of medium hardness can be produced by intended mixing of hard and soft straight run bitumen.

The precipitation and extraction methods produce hard bitumen grades by special temperature dependent air-blowing procedures.

2.2 Chemical-physical properties

Bitumen grades are clearly distinguished by their chemical-material composition and the molecular-physical structure. They form colloidal systems, in

which high-molecular hydrocarbons and low-mole-cular constituents are present fine distributed in form of multiple and complex combined groups of substances.

Structurally the groups of substances form a two-phase system consisting of a coherent outer phase and an inner phase dispersed therein. The bitumen constituents of the coherent phase mainly consist of low-molecular high-boiling oils, known as malthe-nes. The dispersed phase is mainly a combination of high-molecular asphaltenes, which are highly polymerised and precipitate if the soluble petroleum resins are diluted when dissolving the bitumen in a solvent.

The characteristic physical-chemical properties of the bitumen depend on the chemical-material composi-tion, the quantitative ratio of the participating groups of substances and the temperature dependent stabi-lity of the molecular structure. The orientational struc-ture of the molecules is subject to the influences of the intermolecular effective forces and the temperature. The orientational stability decreases with increasing temperature, the asphaltenes become mobile and the bitumen becomes softer. This high dependence on temperature determines the plastic behaviour of the

Bitumen and bituminous binders (acc. to Lit.4) Fig. 80

Bitumen Bituminousbinders

Straightrun

bitumen

Straightrun

bitumen

Precipita-tion

bitumen

Pavingbitumen

Industrialbitumen

Bitumensolutions

Bitumenemulsions

Polymermodified bitumen

Vacuum bitumen

Hard-bitumen

Bitumen antistripping

agent

Fluxedbitumen

Cut-backbitumen

Bitumen paint

bymanufacturing method

byfields of application

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85

bitumen grades. This is why bitumen grades with a low proportion of asphaltenes are highly fluid at high tem-peratures, but turn brittle and hard at low temperatu-res. In contrast to this, bitumen with high proportions of asphaltenes and oil as well as a low proportion of petroleum resin reveals a highly plastic behaviour. The more stable the structure of the asphaltenes, the more plastic the behaviour of the bitumen.

The characteristic influence of temperature also deter-mines the rheological properties of the bitumen grades, the behaviour of which stretches via the visco-elastic range all the way to a plastic behaviour, similar to a Newton‘s fluid (Lit. 38). The rheological behaviour of elasto and visco-plastic substances is generally cha-racterised by the rudimentary interrelationships (mass laws) between shearing stress, viscosity and of defor-

2.3 Tests

Chemical and physical methods are applied to examine the characteristics of bitumen. In accordance with the purpose these are testing methods for the iden-tification and determination of the chemical-material composition, for the reason of safety when handling bitumen and for the determination of material specific

mation rate. For the rheological behaviour of bitumen these mass laws are schematically presented in Fig. 81. Ageing of bitumen is expressed through solidification and a loss of bonding strength. It is caused by che-mical and / or physical processes, whereby time, heat, atmospheric oxygen and light with its ultraviolet rays are significant contributing factors. The temporal ageing of bitumen under the condition of rest causes solidification as a result of physical changes in the structure, which may be reversible under the influence of heat and / or mechanical loads. Temporal ageing depends e.g. on the loss of volatile oils, polymerisation of reactive bitumen constituents, oxidation by absorp-tion of atmospheric oxygen and liberation of hydro-gen.

or engineering related behaviour. The material specific tests aim at the evaluation of the time and tempera-ture dependent mechanical and rheological behaviour, including the resistance against ageing. The general principles of the testing methods are based on empiri-cal knowledge, from which practically applicable sim-

Schematic presentation of the flow behaviour of bitumen acc. to E.J.Barth (Lit. 32) Fig. 81

A= Viscous flow: shearing rate proportional to shearing stress.B= Pseudo-plastic or visco-elastic flow: shearing rate increasing overlinearly with shearing stress. The viscosity decreases with dropping shearing rate and increasing shearing stress.C= Dilatent flow: no proportionality between shearing rate and shearing stress, however, the viscosity

may reach a constant value at high shearing rates.D= Plastic flow: characteristic yield value for the shearing rate, at which a flowing process starts.E= Thixotrope flow: yield value as under D, however, additionally a reversible decrese in viscosity after a shearing stress.


86

plified normative methods and requirements based thereon have developed (T 3, para. 2.4 and 3.3). Some important test methods are listed in table 25; regulati-ons on testing technology see appendix A 4.

Tab. 25: Test methods for bitumen (acc. to Lit. 32)

Explanations to Tab. 25:The test methods listed under points A, B, D and F do not produce any physical magnitudes, but relative parameters.

To A:The flash point identifies the temperature limit at which bitiumen is not yet inflammable. The permissible heating when handling bitumen (storage, pumping) as well as the temperature sensitive foaming reactions of bitumen are strongly influenced by the water content.

To B:These test methods are used to identify the bitumen grades (Fig. 82 and Tab. 26, 27). The penetration speci-fies the degree of hardness of the bitumen. The breaking point indicates the temperature at which the bitumen changes to brittle-hard. The softening point (test with ring and ball) is a temperature limit providing information on the deformability of bitumen in case of softening.

To C:These test methods supplement the identification of the chemical-material composition and provide infor-mation on the origin of the grades of bitumen.

To D:The rheological characteristics of the bitumen grades are detected by the empirical test methods listed under point B as well as by viscometer tests. The tem-perature dependent ductility marks the yield point of the bitumen.

To E:These test methods enable conclusions on the che-mical-material composition of the bitumen grades and on specific substance groups, whereby simple chemi-cal characteristic tests as well as physical measuring methods (infrared spectral analysis, mass spectro-graph, magnetic resonance analysis) are applied.

A. Safety Flash point o.T. °C Water content % by weight

B. Grade designation Penetration 100g/5s/25°C Ring-and-ball softening point °C Fraass breaking point °C

C. Marking (origin) Density at 25°C Sulphur content % by weight Paraffin wax content % by weight Asphaltene content % by weight

D. Rheological test method Viscosity 100, 135, 150°C mm2/s (cSt) Penetration 100g/5s/0°C Penetration 200g/60s/0°C Penetration 50g/5s/46,1, 1°C Ductility 5cm/min, 0-25°C cm Temperature sensitivity Glass transition temperature °C

E. Chemical-material composition Substance group classification % by weight UV analysis Ash content % by weight Insoluble by benzene % by weight Insoluble by cyclohexane % by weight Oliensis spot test Saponifiable proportions % by weight Neutralisation index mg/g Salinity mg/kg

F. Performance related tests Loss of weight 163°C/5h % Properties after the loss of weight test: a) Penetration 100g/5s/25°C b) Softening point ring-and-ball °C c) Fraass breaking point °C d) Ductility 5cm/min, 0-25°C cm Stripping after immersion in water % Loss of compressive strength % Abrasion loss % by weight Foam height cm

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To F:The so-called performance related tests enable addi-tional conclusions on the behaviour of bitumen during the material specific processing, e.g. mixing proces-ses resting time and changing of properties (strength, drive, antistripping and bonding properties).

Penetration in 1/10 mm, by which a standardised needle loaded with 100 g penetrates into bitumen with a temperature of 25°C within 5 seconds.

The temperature at which an evenly warmed up bitu-men layer inside a brass ring deforms under the weight of a steel ball.

2.4 Material specific requirements *

2.4.1 Paving bitumen

Paving bitumens are distillation products from the refi-ning of crude oil. For their requirements the regulations DIN EN 12591 (as replacement for the previous regu-lations DIN 1995) developed in the course of Euro-pean standardisation with a new ordering of the binder grades is valid; overviews see Tab. 26 and 27.

DIN 1995 DIN EN 12591 Grade SP RaB Penetration Grade SP RaB Penetration B 200 37-44 160-210 160/220 35-43 160-220 B 80 44-49 70-100 70/100 43-51 70-100 B65 49-54 50-70 50/70 46-54 50-70 B45 54-59 35-50 30/45 52-60 30-45 B 25 59-97 20-30 20/30 55-63 20-30 Tab. 26 Binder grades and characterising require-ments according to DIN 1995 (old) and DIN EN 12591 (new)

* The tables in T 3, para. 2.4 origin from the currently valid technical regulations (appendix A 4)

Determination of needle penetration Fig. 82a

Determination of the softening point RaB(Ring and Ball) Fig. 82b


88

2.4.2 Special bitumens and bituminous binders

Requirements acc. to DIN 1995 (s. appendix A 4 and Lit. 39)

Fluxed bitumenFlux bitumen is manufactured by adding heavy-liquid flux oils to paving bitumen. These oils reduce the vis-cosity, enabling warm laying of fluxed bitumen.

Bitumen emulsionsBitumen emulsions consist of colloidal solutions of medium hard straight-run bitumen in water, whereby the fine distribution (emulsification) of the binding agent is achieved by adding emulsifying agents and lyes. The alkaline or acidy emulsification reduces the interfacial tension between the bitumen particles and water. Addition of stabilising agents (fine particle clays, betonites) causes the formation of film-like protective sheaths around the bitumen particles, which reduces the interfacial tension even further.

Emulsions are graded according to their viscosity and breaking time (stability up to the desintegration into bitumen and aqueous phase). Bitumen emulsions are processed in cold liquid condition.

Cold bitumenCold bitumen (petroleum cut-back bitumen) is manuf-actured as bitumen solutions using soft to medium hard paving bitumen and adding volatile solvents. Since this reduces the viscosity of the bitumen, these materials can be processed in cold liquid condition.

Polymer modified bitumenThe properties of bitumen can be modified by adding synthetic polymeric materials (elastomeres, thermo-setting plastics and thermoplasts acc. to DIN 7724) or by polymeric waste or side products. These materials must be used according to special technical delivery conditions for the hot laying of asphalt layers and for surface treatments; see appendix A 4.

Bitumen grades 20/30 30/45 50/70 70/100 160/220 Penetration at25°C 0,1mm 20-30 30-45 50-70 70-100 160-220 DIN EN 1426 Softening point °C 55-63 52-60 46-54 43-51 35-43 DIN EN 1427 Resistance to hardening at 163°C (DIN EN 12607-1/3) -Change of mass % 0,5 0,8 1,0 maximum + -Remained penetra- % 55 53 50 45 37 tion, minimum -Softening point after °C 57 54 48 45 37 hardening, minimum Flash point minimum °C 240 230 220 (DIN EN 22592) Solubility, minimum % 99,0 (DIN EN 12592) (m/m) Wax paraffin content % 2,2 (DIN EN 12606-1) Fraaß breaking point °C -5 -6 -10 -15 maximum (DIN EN 12593) Increase in softening °C 8 9 11 point after hardening, maximum

Tab. 27: Requirements for paving bitumen acc. to DIN EN 12591

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3. Asphalt*

3.1 Mineral aggregates

The asphalt consists of mineral aggregates and bitu-men or bituminous binders as described in T 3, para. 2. The general requirements for mineral aggregates used in highway and transportation engineering are

specified in technical product specifications (s. appen-dix A 4).

Important aggregate product sizes: a) non-crushed aggre-gates: gravel and natural sand, b) crushed aggregates: crushed rock, chippings, crushed sand, high-grade chip-pings, high-grade crushed sands, stone dust, filler (Tab. 28).

Tab. 28: Product sizes for mineral aggregates

The technical regulations, which apply particularly for asphalt pavements in highway and transportation engineering, differentiate between natural aggregates (crushed rock, crushed and non-crushed gravel, sand) and artificial ggregates (slags from blast furnaces and steel plants as well as metal slags). Industrial side pro-ducts and recycling materials are alternative highway construction materials.

Requirements concerning maximum density, compres-sive strength and impact resistance see Tab. 29

The aggregates used in surface courses and gritting must have an additional polishing resistance. On the single-size aggregate 8/10 mm the polishing resi-stance is evaluated with the PSV-test (Polished Stone Value), representative for all high-grade coarse frac-tions (see T 3, para. 3.3.1); polishing tests acc. to TP-Min-StB (appendix A 4).

* The tables in T 3, para. 3 are taken from the currently effective regulations (appendix A 4) in connection with Lit. 39 and 40.

Natural sand Crushed sands/chippings Stone dust Gravel Crushed rock High-grade crushed sand High-grade chippings - - Stone dust 0/0,09 mm Natural sand 0/2 mm Crushed sand/chippings 0/5 mm High-grade crushed sand 0/2 mm Gravel 2/4 mm - High-grade chippings 2/5 mm Gravel 4/8 mm Chippings 5/11 mm High-grade chippings 5/8 mm - - - - High-grade chippings 8/11 mm Gravel 8/16 mm Chippings 11/22 mm High-grade chippings 11/16 mm Gravel 16/32 mm Chippings 22/32 mm High-grade chippings 16/22 mm Gravel 32/63 mm Crushed rock 32/45 mm - - - - Crushed rock 45/56 mm -


90

Rock/ Max. density Compress. Resistance rock group strength against impact Crushed rock Crush. rock Chipp./gravel ρR βD SD10 SZ 8/12

g/cm³ N/mm² M.-% 1) M.-% 2) 1 2 3 4 5 1 Granite, granodiorite, syenite 2,60 – 2,80 160 – 240 10 – 22 12 – 27 2 Diorite, gabbro 2,70 – 3,00 170 – 300 8 – 18 10 – 20 3 Rhyolite, rhyodacite, trachyte, phonolite, micro-diorite, andesite 2,50 – 2,85 180 - 300 9 – 22 11 – 23 4 Basalt, melaphyre 2,85 – 3,05 250 – 400 7 – 17 9 – 20 5 Basaltic lava 2,40 – 2,85 80 – 150 13 – 20 16 – 22 6 Lava slag Requirements acc. to MLS 3) 7 Diabase 2,75 – 2,95 180 – 250 7 – 17 9 – 20 8 Lime rock, dolomite rock 2,65 – 2,85 80 – 180 16 – 30 17 – 28 9 Graywacke, quartzite, vein quarz, quartz, sandstone 2,60 – 2,75 120 – 300 10 – 22 12 – 27 10 Gneiss, granulite, amphibolite, serpentinite 2,65 – 3,10 160 – 280 10 – 22 12 – 27 11 Gravel, crushed 2,60 – 275 - - 14 – 24 12 Gravel, round 2,55 – 2,75 - - 17 – 34 13 Metal slag MHS-1 3,40 – 4,00 > 150 15 – 24 18 – 25 14 Metal slag MHS-2 2,60 – 3,50 > 80 20 – 33 22 – 34 15 Blast furnace slag HOS-A 2,40 – 2,80 - 15 – 24 18 – 25 16 Blast furnace slag HOS-B 2,10 – 2,60 - 20 – 33 22 – 34 17 Blast furnace slag HOS-C 2,10 – 2,60 No tests and parameters 18 Steel plant slag 3,20 – 3,60 - 12 – 29 10 – 26 19 Ash from incineration of domestic waste - - - ≤ 40 20 Recycling materials - - ≤ 33 ≤ 28

Explanations to Tab 29: 1) SD 10 Resistance of crushed rock against crushing during the impact test (DIN 521156-2) 2) SZ 8/12 Resistance of chipping or gravel ageinst crushing during the impact test (DIN EN 1097-2) 3) MLS Information leaflet on lava slag in highway and transportation engineering

Tab. 29: Requirements for mineral aggregates acc. to German TL Min 2000

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3.2 Asphalt for base courses

In their function of main load bearing elements in high-way pavements the asphalt base courses protected by surface course and binder course have load distribu-ting functions. The mixture consists of aggregates and paving bitumen as binder (T 3, para. 3.1 and 2.4.1).

Mixture types are classified under specific aspects of the intended use: for components and properties refer to Tab. 30.Requirements for the asphalt base course:The thickness of each course or layer must be at least 8 cm, 6 cm for regulating courses and at least 2.5 times the diameter of the largest particle.

Degree of compaction for mix type CS, C, B: > 97%for mixture type A, AO: > 96%Deviation from specified thickness: < + 1,0 cmUnevenness under a 4 m straight edge: < 1,0 cmLaying thickn./weight mean value, undercut: < 10%Laying thickn. single value, undercut: < 2,5 cm

Asphalt base courses are laid down and compacted hot (Fig. 83). Experience values for lowest and highest mix-ture temperatures according to technical regulations:

Binder grades: Temperature °C1)

B 80 120 – 180 B 65 120 – 180 B 45 130 – 190

1) Upper temperature when receiving the mixture at the mixing plant or silo, lower temperature for the time of laying.

Type of Particle Particles Particles Coarsest Oversize Minimum Marshall Marshall Air void mixture size > 2 mm < 0,09 mm particle particle binder stability flow content minimum maximum content at 60°C minimum mm weight % weight % weight % weight % weight % kN mm Vol.-% 1 2 3 4 5 6 7 8 9 10 AO 0/2 bis 0/32 0 bis 80 2 bis 20 10 20 3,3 2,0 1,5 bis 4,0 4,0 bis 20,0 A 0/2 bis 0/32 0 bis 35 4 bis 20 10 20 4,3 3,0 1,5 bis 4,0 4,0 bis 14,0 B 0/22; 0/32 über 35 bis 60 3 bis 12 10 10 3,9 4,0 1,5 bis 4,0 4,0 bis 12,0 C 0/22; 0/32 über 60 bis 80 3 bis 10 10 10 3,6 5,0 1,5 bis 4,0 4,0 bis 10,0 CS 0/22; 0/32 über 60 bis 80 3 bis 10 10 10 3,6 8,0 1,5 bis 5,0 5,0 bis 10,0

Explanations to Tab. 30:1) Mixture type AO only for full depth asphalt pavements 2) Mixture type A only for lower layer of base course3) Mixture type CS for construction class SV and traffic areas subject to special loads: minimum 60% crushed particles bigger than 2 mm, ratio of crushed sand to natural sand at least 1:14) Mixture types B, C, CS for all other pavements or construction classes (B limited)5) For the use of paving bitumen6) Determination on Marshall samples (see T 3, para. 4.1)

Tab. 30: Components and properties of bearing course mixtures

Compaction of the asphalt base coursewith using a 8 t VARIOMATIC roller Fig. 83


92

The permissible laying thickness for the relatively thin surface courses depends mainly on the particle size of the mixture (Tab. 32), independently from the standar-dised thickness specified in T 3, para. 1.

mm cm Asphalt concrete 0/5 1,5 – 3,0 0,8 2,5 – 4,5 0/11 3,0 – 6,0 0/11 S 4,0 – 5,0 0/16 S 4,0 – 7,5 Stone mastic asphalt 0/5 1,0 – 3,5 0/8 S 2,0 – 5,5 0/11 S 2,5 – 7,0Tab. 32: Experience values of mat thicknesses for sur-face courses

The stability of asphalt surfacings (asphalt binder courses and surface courses) made of rolled asphalt can be impro-ved by a favourable adjustment of the proportions of chip-pings and crushed sand as well as the use of high-grade aggregates with a higher proportion of crushed surfaces, whereas the durability can be enhanced by a perfect adap-tation of the binder content to the air void content (Lit. 35). Hard binders or low binder contents, as may be conside-red for high traffic loads, contribute to the potential of crak-king.

The stability and durability of gussasphalt depends to a great extent on the interaction between binder and filler and their homogeneous distribution in the chippings/sand particle skeleton. For the polishing resistance of high-grade chippings in surface courses and for the spreading of chippings certain PSV-values are demanded:

3.3 Asphalt for surfacing

3.3.1 General requirements

The required composition of the asphalt for surface courses and binder courses depends substantially on the type of traffic load and the construction class. The overview in Tab. 31 specifies nominal aggregate sizes for asphalt binder courses and surfaces courses, as well as for various types of mixtures, depending on the traffic load. The mixtures marked S, which are charac-terised by a higher stability and require a sufficiently

designed binder course and base course, are recom-mendet for the use for construction classes SV, I, II, III and St SLW.

Traffic load Constr. class/ Asphalt Asphalt Stone mastic Gussasphalt traffic area binder concrete asphalt normal SV + 1 0/22 S - 0/11 S 0/11 S or special II 0/16 S 0/11 S 0/8 S special III + St SLW 0/16 s 0/11 S 0/11 S, 0/8 S 0/11 S III + IV 0/16 0/11 0/8 1)

normal V +VI - 0/11, 0/8 0/8, 05 1)

St LLW, cycle and - 0/11, 08, 0/8, 0/5 1)

sidewalks - 0/5

Explanations to Tab. 31: Figure1) Use only in exceptional cases for gussasphalt with aggregate sizes of 0/8 or 0/11 mm, for cycle paths and sidewalks 0/5 or 0/8 mm.

Tab. 31: Rock particle fractions for asphalt binders and surface courses in dependence on loads

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- Construction class III – VI with normal traffic load PSV > 43- Construction class SV, I, II as well as for highways of construction class III subject to special loads PSV > 50

The deformation resistance of asphalt surface courses is substantially influenced by the temperature of the mixture and, during laying, by its cooling and rehea-ting (Lit. 36). During mixing and laying certain maxi-mum and minimum temperatures must therefore be complied with, in dependence of binder grade and type of mixture (Tab. 33)

Further information on the effect of temperature see T 3, para. 4.2.2.

Tab. 33: Reference values for permissable mixture temperatures for asphalt binder and asphalt surface courses

Type of Asphalt Asphalt Stone Guss- Asphalt Combined Asphalt binder binder concrete mastic asphalt mastic surface - concrete (hot asphalt base - (warm laying) course laying) B 25 200-250 B 45 130-190 140-190 200-250 180-220 B 65 120-180 130-180 150-180 200-250 180-220 B 80 120-180 130-180 150-180 180-220 120-180 B 200 120-170 120-170 170-210 100-170 FB 500 60-130

Explanations to Tab. 33: 1. The top temperature when receiving the mixture at the mixing plant or silo, the lower temperature for the time of laying. 2. When exceeding the top temperature bitumen may harden and lose its bonding strength. When cooling down below the lower temperature the viscosity of bitumen increases. This may considerably impair the workability and rolling may become in-effective.


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3.3.2 Binder course asphalt

Components and properties as well as course require-ments see Tab. 34.

Tab. 34: Binder course asphalt

The mixture for asphalt binder courses is hot manu-factured and laid by pavers and compacted with rollers (Fig. 84). Experience values for lowest and highest mixture temperatures acc. to the technical regulati-ons:

Binder grade Temperature °C 1)

B 80 120 – 180 B 65 120 – 180 B 45 130 – 190

1) The top temperature when receiving the mixtureat the mixing plant or silo, the lower temperature for the time of laying.

0,22 S 0/16 S 0/16 0/11 Mineral aggregates High-grade chip., high High-grade chip., high-grade crushed grade sand, stone dust sand, natural sand, stone dust Particle size fraction mm 0/22 0/16 0/16 0/11 Part. prop. < 0,09 mm % by weight 4 to 8 4 to 8 3 to 9 3 to 9 Part. prop. > 2 mm % by weight 70 to 80 70 to 75 60 to 75 50 to 70 Part. prop. > 8 mm % by weight - - - > 20 Part. prop. > 11,2 mm % by weight - > 25 > 20 < 10 Part. prop. > 16 mm % by weight > 25 < 10 < 10 - Part. prop. > 22,4 mm % by weight < 10 - - - Crushed sand/natural sand ratio 1:0 1:0 > 1:1 > 1:1 Binder Grade B 45, PmB 45 B 45, PmB 45 B 65, B 80 B 65, B 80 Binder content % by weight 4,0 to 5,0 4,2 to 5,5 4,0 to 6,0 4,5 to 6,5 Mixture Air void content of the Marshall specimen Vol.-% 5,0 to 7,0 5,0 to 7,0 3,0 to 7,0 3,0 to 7,0 Course Course thickness cm 7,0 to 10,0 5,0 to 8,5 4,0 to 8,5 only for profil regu- or lating, not for laying weight kg/m2 170 to 250 125 to 210 95 to 210 classes SV. I to III and highways with special loads Degree of compaction % > 97 > 97 > 97 > 97 for thickn. up to 3 cm

Compaction of an ashalt binder courseusing a 2.5 t vibratory roller Fig. 84

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3.3.3 Asphalt concrete


Tab. 35: Asphalt concrete

1) Construction class III

The mixture is hot manufactured, laid by pavers and compacted with rollers (Fig. 85). Spreading of crushed sand or fine chippings onto the hot surface before or during rolling enhances the initial grip of the surface course. Asphalt concrete can be laid warm in excep-tional cases, e.g. as surface courses for low volume highways and agricultural roads.

0,16 S 0/11 S 0/11 0/8 0/5 Mineral aggregates High-grade chipping, high grade crushed sand, natural sand, stone dust Paricle size fraction mm 0/16 0/11 0/11 0/0 0/5 Part. prop. < 0,09 mm % by weight 6 to 10 6 to 10 7 to 13 7 to 13 30 to 50 Part. prop. > 2 mm % by weight 55 to 65 50 to 60 40 to 60 35 to 60 Part. prop. > 5 mm % by weight - - - > 15 > 10 Part. prop. > 8 mm % by weight 25 to 40 15 to 30 > 15 < 10 - Part. prop. > 11,2 mm % by weight > 25 < 10 < 10 - - Part. prop. > 16 mm % by weight < 10 - - - - Crushed sand/natural sand ratio > 1:1 > 1:1 > 1:11) > 1:11) - Binder Grade B 65 B 65 B 80 B 80 B 80 Binder content Gew.-% 5,2 - 6,5 5,9 - 7,2 6,2 - 7,5 6,4 - 7,7 6,8 - 8,0 Mixture Air void content of the Marshall specimen Vol.-% a class SV, I, II, III S, IV S, u. St SLW 3,0 to 5,0 3,0 to 5,0 b class II u. IV 2,0 to 4,0 2,0 to 4,0 c. class V, VI, rural roads 1,0 to 3,0 1,0 to 3,0 1,0 to 3,0 Course Course thickness cm 5,0 - 6,0 4,0 - 5,0 3,5 - 4,5 3,0 - 4,0 2,0 - 3,0 or laying weight kg/m2 120 - 150 95 - 125 85 - 115 75 - 100 45 - 75 Degree of compaction % > 97 > 97 > 97 > 97 > 96 Air void content Vol.-% < 7,0 < 7,0 < 6,0 < 6,0 < 6,0

Compaction of ashalt concreteusing a 12 t VARIOMATIC roller Fig. 85


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3.3.4 Stone mastic asphalt


Tab. 36: Stone mastic asphalt

High binder contents with stabilising additives are cha-racteristics for this mixture. The hot mixture is laid down by pavers and, due to its composition of high stiffness, it must be intensively compacted with heavy rollers. Crushed sand or chippings spread over the hot surface and rolled in enhances the initial skid resi-stance (Fig. 86).

0,11 S 0/8 S 0/8 0/5 Mineral aggregates High-grade chip., high High-grade chip., high-grade crushed grade sand, stone dust sand, natural sand, stone dust Particle size fraction mm 0/11 0/8 0/8 0/5 Part. prop. < 0,09 mm % by weight 9 to 13 10 to 13 8 to 13 8 to 13 Part. prop. > 2 mm % by weight 75 to 80 75 to 80 70 to 80 60 to 70 Part. prop. > 5 mm % by weight 60 to 70 > 55 45 to 70 < 10 Part. prop. > 8 mm % by weight > 40 < 10 < 10 - Part. prop. > 11,2 mm % by weight < 10 - - - Crushed sand/natural sand ratio 1:0 1:0 > 1:1 > 1:1 Binder Grade B 65 B 65 B 80 B 80 Binder content % by weight > 6,5 > 7,0 > 7,0 > 7,2 Stabilising additives Content in mixture % by weight 0,3 bis 1,5 Mixture Marshall specimen: Compaction temperature °C 135 + 5 135 + 5 135 + 5 135 + 5 Air void content Vol-% 3,0 to 4,0 3,0 to 4,0 2,0 to 4,0 2,0 to 4,0 Course Course thickness cm 3,5 to 4,0 3,0 to 4,0 2,0 to 4,0 1,5 to 3,0 Laying weight kg/m2 85 to 100 70 to 100 45 to 100 35 to 75 Course thickness cm 2,5 to 5,0 2,0 to 4,0 - - Laying weight kg/m2 60 to 125 45 to 100 - - Degree of compaction % > 97 Air void content Vol.-% < 6,0

Compaction and gritting ofstone mastic asphalt Fig. 86

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3.3.5 Gussasphalt


Tab. 37: Gussasphalt

The mixture is hot manufactured, transported to the site in heated transportation tanks with stirring equip-ment and laid down by means of a machine driven screed. In the areas of the traffic lanes the hot sur-face is gritted with chippings, in other areas the grip is enhanced with sand.


0,11 S 0/11 0/8 0/5 Mineral aggregates high-grade chip., high-grade crushed sand, natural sand, stone dust Particle size fraction mm 0/11 0/8 0/5 Part. prop. < 0,09 mm % by weight 20 to 30 22 to 32 8 to 13 Part. prop. > 2 mm % by weight 45 to 55 40 to 50 60 to 70 Part. prop. > 5 mm % by weight - > 15 - Part. prop. > 8 mm % by weight > 15 > 10 < 10 Part. prop. > 11,2 mm % by weight < 10 - - Crushed sand/natural sand ratio > 1:2 - - - Binder Grade B 45 B 45 Binder content % by weight 6,5 to 8,0 6,8 to 8,0 7,0 to 8,5 Softening point RaB after extraktion °C < 70 < 70 < 70 < 70 Mixture Indentation test 5 cm2 at 40°C on sample cube after 30 min. mm 1,0 to 3,5 1,0 to 5,0 1,0 to 5,0 1,0 to 5,0 Increase after another 30 min. mm < 0,4 < 0,6 < 0,6 < 0,6 Course Course thickness (incl. gritting material) cm 3,5 to 4,0 2,5 to 3,5 2,0 to 3,0 or laying weight (incl. gritting material kg/m2 80 to 100 65 to 85 45 to 75 Gritting material/quantity High-grade chippings 2/5 mm 5 to 8 kg/m2

High-grade chippings 2/5 and/or 5/8 mm 15 to 18 kg/m2

High-grade crushed sand or natural sand 2 to 3 kg/m2

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3.3.6 Asphalt mastic


Tab. 38: Asphalt masticThe mixture is hot manufactured, transported in moto-rised boilers with permanent stirring and distributed after pouring. Binder coated high-grade chippings are spread over the hot surface and immediately rolled into the mastic down to the substrate.

3.3.7 Combined surface-base-courses

Components and properties as well as layer require-ments see Tab. 39

Tab. 39: Combined surface-base-coursesCombined surface-base-courses are used as single layer pavements on low volume roads as well as for cycle paths and sidewalks. The mixture is manufactu-red, placed and compacted hot.

3.3.8 Natural asphalt and modified asphalt

(1) Natural asphalt

Natural asphalt is added to gussasphalt, stone mastic asphalt and mortar enriched asphalt concrete among others, e.g. as natural Trinidad-asphalt (épuré, flour). These additives can enhance the stability of the sur-face course or binder course and have a positive effect on processing and compaction.

(2) Elastomere modified asphalt

The mechanical and elastic properties of rolled asphalts can be modified by adding caoutchouc or rubber. This improvement is particularly related to ela-sticity, adhesion strength, ageing resistance against water and weather influences as well as fatigue resi-stance.

(3) Polymer modified asphalt

The use of polymer modified bitumen or the addition of polymeres enhance the adhesive properties, the stability and elasticity and, when increasing the binder content, even the ageing resistance and durability against the influence of water and weather.

3.3.9 Asphalts for special construction methods

(1) Vibro asphalt (rolled poured mastic asphalt)

The mixture consists of approx. 60% chipping, 10% filler, equal proportions of crushed and natural sand as well as approx. 6.4% binder B 45. It is mixed at a temperature of approx. 230°C and transported with insulated special trucks. During laying with a paver the mixture is liquified and compacted by vibration and chippings are subsequently spread over this poured mastic asphalt like surface and rolled in.

(2) Drainage asphalt (porous asphalt)

The mixture for drainage asphalt surface courses is combined of a high quantity of chippings with a highly resistant binder and mortar. It is then applied as a surface course on a dense substrate or an additional

0/2 Mineral aggregates Natural sand or natural sand and high-grade crushed sand, stone dust Particle size fraction mm 0/2 Part. prop. < 0,09 mm % by weight 30 to 60 Part. prop. > 2 mm % by weight < 15 Binder Grade B 65, B 80 Binder content % by weight 13,0 to 18,0 Mixture Softening point Wilhelmi °C suitability test Course Laying weight of asphalt mastic kg/m2 15 to 25

0/2 Mineral aggregate Natural sand or natural sand and high-grade crushed sand, stone dust Particle size fraction mm 0/16 Part. prop. < 0,09 mm % by weight 7 to 12 Part. prop. > 2 mm % by weight 50 to 70 Part. prop. >11,2 mm % by weight 10 to 20 Part. prop. >16 mm % by weight < 10 Binder Grade B 80, B 200 Binder content % by weight > 5,2 Mixture Air void content of Marshall specimen Vol.-% 1,0 to 3,0 Marshall stability kN > 4,0 Marshall flow mm 2,0 to 5,0 Course Coursethickness cm 5,0 to 10,0 or laying weight kg/m2 120 to 250 Degree of compaction % > 96 Air void content Vol.-% < 7,0

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waterproofing layer. This type of asphalt is characte-rised by a higher content of air voids which enhances the drainage between the surface of the carriageway and the vehicle tires. It also changes the thermal con-ductivity and the low temperature performance.

(3) Cold laying in thin layers

Cold mixed asphalt consisting of mineral aggregates 0/3 to 0/8 mm, water, polymer modified cationic bitu-men emulsion and additives is mixed and placed with a laying weight of 10 to 30 kg/m² (dry mass), using special self-propelled mixing and paving equipment. The necessary bonding between the layers requires an absolutely clean substrate.

(4) Hot laying in thin layers

Hot placed thin layers consist of asphalt concrete, stone mastic asphalt or gussasphalt and are applied with a laying weight of 30 to 50 kg/m², depending on load and condition of the substrate.

3.4 Asphalt veneer coats

Asphalt veneer coats are placed on surface courses in order to seal these surfaces or to enhance their grip. They are applied as so-called surface treatment or in form of thin layers by cold laying. This treatment is applied as protection against the influence of weather and traffic loads and against moisture, mainly on low volume traffic areas (construction classes IV to VI), as well as for sidewalks and yards, but not as an indepen-dent surface course.

For surface treatment the substrate or the previously spread chippings are sprayed with a bituminous binder agent and subsequently gritted once or twice with raw or coated chippings.

Cold placed thin layers are mixtures consisting of mineral aggregates (high-grade chippings, high-grade crushed sand and reclaimed filler), polymer modified cationic bitumen emulsions, additives and water; see T 3, para. 3.3.9.


100

leaflet on the compaction of rolled asphalt mixtures is described by an exponential formulation, derived from the bulk densities ρA of Marshall specimen (T 3, para. 4.2) produced by compaction work S of various extent according to DIN 1996, T. 4. This exponential regularity has the following form

ρA(S) = ρA∞-(ρA∞-ρAO) . e [g/cm3].

4. Compaction characteristics of asphalt

4.1 Fundamentals

After laying asphalt layers must be compacted to achieve stability and reduce air voids to a minimum, in order to avoid subsequent compaction or deformation under the influence of traffic loads and climatic condi-tions, which could impair the suitability of traffic areas or reduce their durability. Purpose of the compaction of asphalt layers is therefore the production of a load related high density and a reduction of the air void content in the asphalt mixture that is adapted to the required binder content. Compaction requirements see tables in T 3, para. 3.2 and 3.3 as well as para. 4.4.

The required compaction work depends on the pro-perties and workability of the asphalt mixture, as well as the thickness of the asphalt layer to be compacted. The compaction effect is influenced by the laying con-ditions as well as by the effectiveness of compaction machine and compaction technique.

The compaction characteristics differ considerably in dependence on the composition and the temperature dependent deformation resistance of the asphalt mix-ture. The term compactibility describes the tempera-ture dependent characteristic of increasing the density of an asphalt under the influence of defined com-paction work. In dependence on the deformation resi-stance a differentiation between easy and difficult to compact mixtures can generally be made: a) Easily compactible mixtures show a high increase in density right at the beginning of the compaction process, follo-wed by an early end of this increase. b) Relatively low density increase rates from the beginning right to the end of the compaction process are characteristic for difficult to compact mixtures, whereby a considerably higher number or more powerful compaction passes and a longer work process is required. In both cases the increase in density decreases over the course of the compaction process.

When considering that the bulk density ρA = f (Z, A, T) is a function of mixture composition Z, compaction work A and temperature T, the interrelations can be combined in a formula. According to Lit. 31, 34 and the

Compaction resistance C and bulk density ρA in depen-dence on compaction work for two mixture variants with identical initial and final density Fig. 87

ρA(S) = Bulk density in dependence on the performed compaction work in g/cm3,S = Compaction work [42 Nm], number of compaction blows per side of specimen,ρA∞ = max. mathematically achievable bulk density in g/cm3 (ρA(S = ∞ )).ρAO = math. initial bulk density at the beginning of the compaction process in g/cm3 (ρA(S = 0 )).C = Compaction resistance determined by change in density.

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According to Fig. 87 the compaction resistance C cha-racterises the permanent change in bulk density ρA during the compaction process or the interrelation bet-ween density and compaction work S. The so-called relative compaction potential is defined as a derived magnitude:

P = (ρA ∞ - ρA o ) / ρA∞

By definition the density is mathematically determined as quotient from mass and volume V.

m m ρA (S) = = V (S) F · d (S)

m = Mass of specimen,F = Base of form cylinder (Marshall)d(S) = Thickness of specimen depending on the applied compaction work.

Since m and F are of constant size, the change in density in dependence on the compaction work is only characterised by the thickness of the specimen or its reciprocal value 1/d. The above mentioned exponen-tial approach for ρA can also be applied to the recipro-cal value of the specimen thickness 1/d:

1 1 1 1 = – – e [mm-1] d(S) d∞ d∞ do

d (S) = Specimen thickness in dependence on the applied compaction work in mm, S = Compaction work [21 Nm], number of compaction blows, d∞ = mathematically determined achievable minimum specimen thickness in mm (d(S = ∞)), do = mathematically determined initial thickness at the beginning of the compaction process in mm (d(S=0)), D = Compaction resistance determined by the change in thickness

Test specific dimensions for the sizes C, D, see T 3, para. 4.2

Similar regularities as for the simulation of compac-tion in a laboratory apply analogue for asphalt com-paction with rollers after the laying of asphalt. For a practical application of laboratory results the number of compaction blows must be converted to the number of rolling passes of the compaction machine using so-called equivalent rolling work. This equivalent rol-ling work specifies the required double-blows perfor-med with a Marshall hammer to achieve an identical change in density on the specimen under identical conditions as by a rolling pass with the compaction machine.

4.2 Test methods

4.2.1 Marshall stability and flow

Marshall stability and Marshall flow are used as para-meters for the resistance of hot placeable rolled asphalt mixtures against mechanical loads. The cor-responding test methods (DIN 1996, T. 11) are most suitable for hot placed mixtures graded in accordance with the asphalt concrete principle, containing not more than 15% particles bigger than 22.4 mm. These methods are therefore not suitable for gussasphalts and mastic asphalt.

The Marshall stability is the maximum force related to specimen height of 63.5 mm, which is measured during a compression test on a cylindrical specimen with partly restricted lateral expansion. During the compression test the specimen is positioned between pressure shells (Fig. 88). From the force-deformation diagram the max. recorded force can be determined as Marshall stability on 0.1 kN (Fig. 88).

[ ] SD–


102

The Marshall flow is the deformation in direction of load application measured when the maximum force is rea-ched. From the diagram the flow can be determined as a distance in 0.1 mm, situated between the distinct deviation of the curve from the neutral axis and the point of the maximum force (Fig. 88).

4.2.2 Compactibility

The standard compaction work required for the prepa-ration of specimens in accordance with the Marshall test method (DIN 1996, part 4 and Lit. 33) is used as comparison and reference magnitude for the compacti-bility of asphalt mixtures (Fig. 86). Marshall specimens are prepared using a standard method (diameter 101.6

mm, normal height 63.5 mm). The hot mixture is com-pacted inside a cylindical mould from each side of the specimen with 50 blows of a 4.5 kg drop hammer falling from a height of 46 cm. Layer thickness, bulk density and air void content of the specimen are thereby eva-luated as a measure for the achieved compaction. The maximum bulk density achieved by this test serves also as reference value for the determination of the degree of compaction of the laid and compacted asphalt (DIN 1996, T. 7). This parameter specifies the percentage of the bulk density ρA which must be achieved or is required as standard after laying and compacting the asphalt. For the determination of the achieved degree of compaction cores or other geometric samples must be taken.

On the basis of the theoretical regularities described in T 3, para. 4.1 the compaction resistances C and D of rolled asphalt mixtures can be examined by using the interrelation between change in density or the change in thickness of Marshall specimen in dependence on the compaction work (Lit. 31, 33, 34 and leaflet on the compaction of asphalt).

Schematic example for the compression deviceby Marshall (DIN 1996) Fig. 88

Marshall method for the determination of thecompactilitiy of asphalt mixtures Fig. 89

4,5 kg Falling weight460 mm Falling height

Standard: 50 Impacts per sideModified: 75 Impacts per side

Specimen

Bulk densitiy ρA

Bulk densitiy drill core ρA‘

Degree of compact. k =ρA‘ρA

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During the test procedure for the determination of the change in thickness, the thickness of the specimen is continuously measured after each compaction blow. The reciprocal values for these thicknesses are appro-ximised with the help of the function specified in T 3, para. 4.1, in dependence on the compaction work. Magnitude D is determined as measure for the compactibility.

In test method for the detection of the change in den-sity, Marshall specimen are prepared with a different number of compaction blows from each side, in order to determine the bulk densities. The bulk densities are approximised in dependence on the number of blows, using the exponential function in T 3, para. 4.1. The interrelation is then quantified with the help of magni-tude C. The dimension of magnitude C complies with the test specific compaction work and, for 2 blows per specimen side with a dropping mass of 45.4 N drop-ping from a height of 0.46 m, results in: 2 x 45,5 x 0,46 = 42 Nm.

4.3 Influencing factors

In laboratory simulation as well as during the laying of asphalt the compaction process is influenced by a number of factors, which interact integrally in a very complicated manner and can only be examined sepa-rately in the analysis. Both the mixture components as well as the compaction temperatures belong to the factors with highest influence (Lit. 33, 34, 36 and leaf-let on the compaction of asphalt).

Pictorial representation of the influence of mineral aggregates on the compaction resistance Fig. 90

Easy to compact:

Difficult to compact:

Crushed sand High chip. cont. Big max. part size Low filler content

Natural sand Low chip. cont. Small max. part. size High filler content

4.3.1 Composition of mixture

By experience, mixture components and mineral aggre-gates in particular have the most significant influence on the compaction resistance (Fig. 90). The mechanical properties of the mineral aggregates influence the com-pactibility in such a way, that, due to their lower inherent friction and interlocking resistance, round particle mix-tures are easier to compact than mixtures consiting of crushed particles. Sand particle and chipping fractions thereby have the strongest effect, whereby the compac-tion resistance mainly rises with the increasing propor-tion of crushed sand or a high content of chippings.

With a decreasing coarse particle fraction bigger than 2 mm the so-called mortar components (binder, sand, filler) gain a higher influence with mixture types com-posed according to the asphalt concrete principle, whereas the compaction resistance does not increase to such an extent when increasing the coarse particle content. Mixtures with a very high proportion of chip-pings (stone mastic asphalt and drainage asphalt) are also mainly influenced by the high mortar content.

The influence of the filler with its stabilising effect on the compactibility of the mixture is only of minor signi-ficance, but is effective in the entirety of the mortar components, whereby the compaction resistance of the mixture decreases with increasing mortar content.

The compaction resistance is highly influenced by the binder content, however, the grade of binder is only of minor signi-ficance. The sliding resistance on the contact faces decreases with increasing thickness of the binder film on the particle sur-faces, which enhances the compaction of the mixture.


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4.3.2 Influence of the temperature

The highly temperature dependent properties of the bituminous binders in turn result in a significant influ-ence of the temperature on the compaction characte-ristics of the mixture. The temperature of the mixture is a very sensitive influential factor, which has an effect in combination with the mixture composition and the temperature dependent variable viscosity of the binder:

With increasing compaction resistance the mixture specific critical compaction temperature rises to a level, where an effective compaction of the mixture is no longer possible. For a difficult to compact mix-ture type the compaction temperature must therefore not drop below a critical limiting value. The required minimum temperature is considerably higher than for easily compactible material. The critical temperature limits must be carefully evaluated by suitability tests and monitored during the laying and compaction of the asphalt by measurements.

Under aspects of compaction practice the tempera-ture shall be as high as permissible at the beginning of compaction work, since this is of advantage for the compaction effect. The top temperature limit is specified because of the fact that the mixture must remain stable under the influence of the roller and that an effective particle redistribution and reduction of air voids occurs during compaction must be accom-plished without any shoving or lateral displacement of the mixture. Depending on the grade of binder the normal temperature when tipping the mixture into the paver is 150 – 180°C, the compaction temperature range approx. 130 – 170°C. In the temperature range between 90 - 100°C compaction must be finished, because a further drop in temperature will result in an excessive increase of the binder viscosity, making com-paction work almost ineffective (Fig. 91).

The temperature influence has an effect on the layer thickness of the asphalt mixture. The thicker the layer, the slower it cools down, the longer the mixture remains compactible and the less weather sensitive are laying and compaction.

Compaction effort and temperature limits formixtures with bitumen B 65 bis B 200 Fig. 91

Mixture temperatureCo

mpa

ctio

n ef

fort

End of Compaction

most favourablecompactiontemperature

Start ofcompaction

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5. Application and performance of BOMAG compaction technology in asphalt construction

5.1 Planning and fields of application

The laying and compaction of asphalt layers requires thorough planning and preparations. Focal points of this planning are the arrangement of temporal and area related sequences of laying and compaction work as well as the decisions concerning the use of appro-priate equipment for laying and compaction. The per-formances rendered for the delivery and processing of the asphalt must be carefully adjusted under due consideration of the laying and compaction progress as well as the necessary quality assurance activities, so that these processes progress almost continuously without any exceptional downtimes. The optimization of these complex arrangements require exact know-ledge about the material properties of the asphalt mix-ture, the asphalt engineering interrelationships during laying and compaction as well as the required level of quality.

The quality requirements aim at the production of an asphalt pavement of appropriate load bearing capa-city and wear resistance for the traffic area with the required profile and with a permanent evenness and with a homogeneous surface structure with maximum grip.

The load bearing capacity of the asphalt pavement requires a high resistance (stability) against deforma-tion under traffic loads. The demands for stability, wear resistance and durable evenness of the asphalt pave-ment require a high density of the compacted mixture with an inherent interlocking of the particles. The long-term stability of asphalt pavements is assured by an air void content, that is as low as possible, and an effective adhesion between layers. A low content of air voids is also a very important criterion for the weathe-ring resistance and the wear resistance of the asphalt pavement.

The position according to the required profile, the long-term evenness and grip of the surface structure are quality features which comply with the demands of traffic safety and driving comfort. The strived for excel-lent evenness of the surface course can only be achie-ved when the stringend evenness requirements for the lower layers are also met.

The asphalt mixture must be composed, processed and compacted with technical and economical efforts to such an extent, that the above mentioned characte-ristics can be assured. The suitability of the machines used for laying and compaction is of highest signi-ficance in this complex task. Due to the high require-ments placed on the compaction quality of asphalt pavements a careful decision must be made of which compaction machines and compaction technologies are most suitable for the respective construction task (Fig. 92).

Selection criteria for compaction equipment for a certain construction task Fig. 92

Construction task

Type ofmaterial

Compact-ibility

Compactionrequirem.

Siteconditions

Productivecapacity

Economy Availability Experience


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When planning the use of equipment it is necessary to take complex influential factors into consideration. These arise from the mixture composition in question, the laying conditions and the machine related require-ments; overview Tab. 40.

The focal points of the BOMAG compaction technology concentrate on the use of vibratory rollers, as described already in part 1 and part 2. For the compaction of asphalt the tables 41, 42 and 43 first of all provide general recom-mendation for a preselection of machines.

+++ highly suitable + conditionally suitable++ well suitable - not suitable

Tab. 42: Recommendations for the use of BOMAG light equipment for asphalt compaction

Tab. 41: Suitability of compaction machines for various types of application

Asphalt Machine Placement conditions Mineral aggregates Type of roller Condition of • max. particle size • static roller substrate • chippings content • rubber tire roller • stiffness • crushed/natural sand • vibratory roller • roughness • type/content of filler • combination roller Weather conditions Bituminous binder Design characteristics • ambient temperature • type • weight • insolation • quantity • weight distribution • wind • vibrating mass • geometry and Layer thickness Compactibility number of drums or tires Precompaction by Compaction paver temperature Application values • frequency Number of passes • amplitude • tire pressure Rolling technique • rolling speed

Table 40: Factors influencing compaction

Type of machine/ Vibratory Vibratory Single wheel Double Tandem Combination field of application tamper plates vibratory vibratory vibratory rollers rollers rollers rollers Asphalt compaction Highway construction O O X X Airport construction X X Hydraulic engineering/waterproofing X X X Sidewalks and cycle paths, Yard and garage driveways O X X X X Parking lots and industrial yards X X X Minor maintenance and repair work X X X X O O Maintenance and repair work O O O X X X

x = well suitable, 0 = suitable

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5.2 Influences caused by ambient laying and compaction conditions

Stability and evenness of the substrate layers, laying thickness in connection with the available time for compaction, temperature of compaction and weather conditions belong to the most important influential factors contributing to compaction effect, compaction quality and compaction output when placing and com-pacting asphalt layers.

(1) Stability and evenness of the subbase

The stability and evenness of the substrate influ-ences the compaction quality of the asphalt layer. The problem arises mainly on non-uniformly compacted unbound base and subbase courses, in case of effects caused by the subgrate and also on extremely stiff or rigid base courses.

Prerequisite for a proper and optimal compaction of asphalt layers is an even subbase with a uniform load bearing capacity and which is neither soft and yiel-ding, nor rigid in reaction and which does not inhibit any considerably stiffness differences. Critical areas, which do not comply with such conditions, must be subsequently compacted before the laying of mixture or should be enhanced by a replacement of material. Significant unevenness require reworking of the profile before laying. For minor unevenness it may be appro-priate to accept certain thickness deviations in the asphalt layer to applied, if this is permitted by the type of mixture and the biggest particle size of the aggre-gate mixture. Too high stiffness values of thin layers may cause crushing of particles.

Tab. 43: Recommendations for the use of BOMAG heavy equipment for asphalt compaction

+++ highly suitable + conditionaly suitable++ well suitable - not suitable


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(2) Laying thickness

The laying thickness has a considerable effect on the required time for an effective compaction of the asphalt layer. It normally is a magnitude determined by the dimensioning or the quantitative output of the paver. It is, however, mandatory to adapt the laying thickness or paver output to the time required for com-paction or the compaction work; see also point (3) and T 3, para 5.3

Compared with a thick layer, a thin layer cools down very quickly, i.e. in such a case compaction must pro-gress very quickly and the laying temperature of the mixture must be as high as possible. Since cold wea-ther even accelerates this cooling process, laying of thin layers should be avoided under such conditions; see also T 3, para. 4.3.2 and Fig. 90.

Another influence of the laying thickness arises from its relation to the biggest particle size of the mineral aggregate mix of the asphalt, meaning that laying, thickness and biggest particle size must be perfectly

adapted to each other. If this ratio is too small, crus-hing of particles and segregation may occur and the obstructed redistribution of particles may increase the compaction resistance. If, in contrast, the ratio bet-ween laying thickness and biggest particle increases significantly, the stability of the asphalt layer will be impaired or reduced. As a general recommendation the laying thickness shall be 3 to 4 times the diamter of the biggest particle in the aggregate mix of the asphalt.

(3) Influences by weathering and temperature

Apart from the laying temperature and the laying thick-ness of the asphalt, the weather conditions have a substantial influence on the cooling of the mixture and thereby on the available compaction time. Speed of wind, air temperature, insolation and temperature of the substrate are contributing factors (Fig. 93).

used too early, the mortar will accumulate at the sur-face, whereby the structural grip will be reduced. In such cases it is important to stabilise the asphalt layer initially by pressing it with a light and statically working roller.

Direct and indirect effects of the weather conditions on the available time for compaction Fig. 93

Under hot weather conditions the cooling process of the asphalt will slow down tremendously, so that thick layers in particular or mixtures with low compaction resistance may not be subjected immediately to the weight of a heavy roller. If heavy rubber tire or vibratory rollers are

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Cold weather promotes the quick cooling of the mix-ture and decisively shortens the time period down to the critical mixture specific minimum temperature, at which further compaction is impossible. This influence increases with the composition related compaction resistance of the asphalt mixture. Under cold weather conditions rolling work must therefore be performed especially quickly and immediately behind the paver and intensified by the use of especially effective com-paction equipment.

Low temperatures also impair or prevent the required adhesion between the layers. Under such conditions prewarming of the substrate or spraying of a bitumi-nous tack coat may be of help.

The compaction and adhesion between layers is also adversely effected if the hot mixture is placed on a wet base, whereby the heat is extracted. If the developing steam has no possibility to escape, blisters and cracks will develop in the asphalt layer. If deposits of water remain on the placed asphalt layer, the layer will cool down more rapidly from the top resulting in an insuf-ficient sealing of pores at the surface and the develop-ment of cracks during the rolling process.

The laying temperature of the mixture and the weather dependent cooling speed have a significant effect on the compaction or the required compaction effort. These inter-relations have already been described in T 3, para. 4.3.2. Further information can be found in T 3, para. 5.3.

The more difficult to compact the the asphalt because of its composition, the higher the required laying tempe-rature. The temperature losses during the transport of the mixture must be maintained at a low level, similar to the temperature losses caused by a heat exchange with the substrate and the outside air or the tempera-ture losses caused by the evaporation of water. The asphalt cools quicker in the upper and lower zones than inside the layer. The required compaction by roller should therefore be finished before the temperature in the in the centre of the layer has dropped below 90 to 100°C (surface temperature approx. 80 to 90°C). For mixture types with a relatively hard bitumen, a high filler proportion and stabilising additives the critical tempe-rature limit is higher. In critical cases it is even more important to utilise the comparably high temperature of the mixture in the paver by intensive compaction close

behind the paver. Regular measurements of the tempe-rature of the mixture inside the paver and in the freshly laid mat are therefore absolutely necessary.

5.3 Area output and volumetric output of the machines

Both area output and volumetric output of the paving and compaction equipment are interdependently rela-ted with each other. During the planning process these two types of output must be exactly adjusted to each other and evaluated (Fig. 94).

The area output of paving depends on the paving width, the working speed and the utilisation rate of the paver. The volumetric output of paving is based on the mixture laying quantity and the area output of the paver.

The area output and volumetric output of compaction machines are influenced by the available rolling time as well as by the number of machines, their mode of operation, the rolling speed and the rolling width. The combination of compaction machines to be used must be selected by due consideration of a number of influencing factors and various quality criteria, such as sufficient compaction, even surface with closed pores, (see T 3, para. 5.1 and Tab. 40).

Laying and compaction of an asphalt binder using2 pavers and five 10 t vibratory rollers, paving width11m, daily output 5000t Fig. 94


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Theoretical area output F and volumetric output M of a paver can be mathematically determined in accor-dance with the leaflet on compaction of asphalt:

F = B . v . fn (m2/h)

F = area output of paver (m2/h)B = paving width (m)v = paving speed (m/min)fn = efficiency factorfn = 0,8 to 1,0 for volumetric output to 100 t/hfn = 0,7 to 0,9 for volumetric output 100 t/h to 200 t/hfn = 0,6 to 0,8 for volumetric output > 200 t/h

F . g M = (t/h) 1000

M = volumetric output (t/h)F = area output (m2/h)g = laying weight (kg/m2).

The following formulas are recommended for the esti-mation of output data:

a) for the area output of a paver when assuming an efficiency factor of fn = 0,83

F = B . v . 50 (m²/h)

b) for the paving speed of a paver

F v = . 0,02 (m/min) B

c) for the area output Fw of a roller:

beff . v . 50 Fw = (m²/h) n

v = mean rolling speed (m/min)n = number of rolling passesb = effective rolling width (m)

d) for the number N of parallel rolled tracks, depen-ding on the paving width B:

B N = 0,9 . b

e) for the effective rolling width

B beff = (m) N

f) for the rolling time t, comprising of pre-rolling, break-down compaction and finish rolling:

L . n . N t = (min) v

L = length of rolling track (m), N = number of rolling tracks, n = number of rolling passes

The practical application of the output formulas men-tioned above requires the consideration of certain fun-damental rules and values of experience:

- The area output of the roller must be evaluated separately for each compaction machine. The total output of all machines used for compaction must be higher than the area output of the paver.

- The area output of the roller decreases when compacting smaller paving widths and when performing special tasks such as the compaction of joints or along edges.

- From practical experience it is recommended to use at least two rollers per paver, if necessary even with different output capacities, in order to be able to per form the required tasks (e.g. breakdown compaction, bonding of layers, closing of pores, connection of joints) in an optimal way and to be able to compensate a possible failure of a machine. Type and number of machines must be chosen in such a way, that the machines will obstruct each other.

- The time required for compaction must be less than the time period during which the mixture will cool down from laying temperature to the critical temperature, at which the mixture can no longer be compacted.

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The compaction conditions can be improved by pre-compaction, intensifying the main compaction process and by using a higher mixture temperature. In this regard it must, however, be noted, that a higher rolling speed can reduce the compaction effect and may, in many cases, cause evenness deficiencies. In accor-dance with Lit. 13 the following speeds are recommen-ded:

Tab. 44: Recommended rolling speeds in accordance with the leaflet on compaction of asphalt

The number of required roller passes can only be esti-mated on the basis of previous experience or must be determined by trial compaction passes. In each indivi-dual case the number of passes depends on the com-paction resistance and the temperature of the asphalt mixture, the mat thickness, the rolling speed, the roller type and the operating mode of the machine. Lit. 13 recommends the values in Tab. 44 for an estimation.

For BOMAG compaction equipment experience values for areal output (m²/h) and volumetric output (t/h) are available. These are listed in Tab. 45 - 48.

Tab. 45: Practical output ranges of compaction equipment in asphalt engineering


70 to 90 m/min (4.2 to 5.4 km/h) for pressing (static) 60 to 90 m/min (3.6 to 5.4 km/h) for breakdown compaction (static) 50 to 80 m/min (3.0 to 4.8 km/h) for breakdown compaction (vibration) 60 to 100 m/min (3.6 to 6.0 km/h) for breakdown compaction (rubber tire roller) 70 to 100 m/min (4.2 to 6.0 km/h) for finish compaction (static) 80 to 120 m/min (4.8 to 7.2 km/h) for finish compaction (rubber tire roller)

Machine type Operat. Areal output weight Compaction capacity (m2/h) with a mat thickness kg 2 - 4 cm 6 - 8 cm 10 - 14 cm

50 - 60 - 20 - 35 20 - 30 70 - 80 - 30 - 40 30 - 35 40 - 100 50 - 100 50 - 80 - 120 - 250 80 - 130 70 - 100 50 - 80

300 - 450 - 90 - 140 80 - 120 600 - 800 - - -

150 - 500 80 - 160 70 - 120 60 - 100 600 - 800 200 - 270 130 - 190 120 - 170

Machine type Operat. Areal output weight Compaction capacity (m2/h) with a mat thickness t 2 - 4 cm 6 - 8 cm 10 - 14 cm

1,5 - 2,5 250 - 450 200 - 350 150 - 300 3,0 - 4,5 400 - 800 250 - 600 250 - 450 7 - 9 600 - 1500 500 - 900 400 - 700

10 - 12 1000 - 2200 800 - 1200 600 - 900 1,5 - 2,5 250 - 450 200 - 300 150 - 250

3,0 - 4,5 400 - 800 250 - 500 250 - 400 7 - 10 600 - 1500 500 - 800 400 - 650


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Machine type Operat. Volumetric output weight Compaction capacity (t/h) with a mat thickness kg 2 - 4 cm 6 - 8 cm 10 - 14 cm

50 - 60 - 3 - 5 6 - 10 70 - 80 - 4 - 6 8 - 10 40 - 100 5 - 10 9 - 15 - 120 - 250 7 - 15 12 - 18 20 - 28

300 - 450 - 16 - 25 25 - 35 600 - 800 - - -

150 - 500 6 - 15 10 - 20 20 - 35 600 - 800 8 - 20 20 - 30 40 - 55 900 - 1200 10 - 25 20 - 35 40 - 65

Machine type Operat. Volumetric output weight Operation capacity (t/h) with a mat thickness t 2 - 4 cm 6 - 8 cm 10 - 14 cm

1,5 - 2,5 10 - 40 25 - 60 40 - 100 3,0 - 4,5 20 - 60 40 - 90 70 - 160 7 - 9 40 - 100 70 - 160 120 - 220

10 - 12 70 - 120 100 - 200 180 - 280 1,5 - 2,5 10 - 35 20 - 55 35 - 90

3,0 - 4,5 20 - 55 35 - 80 65 - 140 7 - 10 35 - 100 60 - 170 90 - 200

Arithmetic example for the planning of rollers (from leaflet on compaction of asphalt)

For the laying of 96 kg/m² asphalt concrete 0/11 with a thickness of 4 cm and a paving width of 3,75 m.Volumetric capacity of paver: 80 t/h.

Procedure:

• Areal output

• Paver speed

• Use of a tandem vibratory roller with a drum width b = 1.42 mRequired number of rolling passes (by experience) n = 2 static + 4 with vibration mean rolling speed v = 70 m/min

• Rolling width

• Arreal output of roller

Since the areal output of the roller (729 m²/h) is lower than the areal output of the paver (833 m²/h), a second roller is required. This roller should also be used to compact joints and edges.

• Rolling time

Here it must be checked whether the available time for an effective compaction in dependence on weather and mat thickness is longer than the calculated rolling time.

M . 1000 80 3 . 1000 F = = = 833 m²/h g 96

F . 0,02 833 . 0,02 V = = = 4,5 m/min B 3,75

B 3,75N = = = 2,9 rounded to 3 = N b . 0,9 1,42 . 0,9

B 3,75 beff = = = 1,25 m N 3

beff . v . 50 1,25 . 70 . 50

F = = = 729 m²/h n 6

L . n . N 50 . 6 . 3 t = = = 12,9 min v 70

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5.4 Compaction equipment (Lit. 25, 27, 28, 37)

5.4.1 Pre-compaction during paving

Pre-compaction of the asphalt mixture with the com-paction screed of the paver (normal screed or high performance screed) generally improves the stability of the fresh and hot asphalt mixture, enables the use of vibratory rollers immediately behind the paver and reduces the compaction effort during rolling. A high pre-compaction with the paver screed also has a posi-tive effect on the achievable evenness of the asphalt course. However, during the subsequent compaction with rollers it must be taken into consideration that the pre-compaction with the paver screed is mostly quite irregular, with lower values in the middle and at the edges of the respective paving width.

The compaction effect depends on the adjustment of the paver screed, the mat thickness and the laying speed, on the stability and evenness of the substrate as well as on the composition and temperature of the asphalt mixture. Under normal conditions up to 82 to 90% of the Marshall density is achieved by pre-com-paction with normal paver screeds whereas high per-formance screeds achieve slightly higher values. The compaction elements of the screed should be adju-stable, so that the compaction effect can be adapted to the influncing factors specified before and an uni-form surface structure is produced over the entire paving area. The uniformity of pre-compaction and the surface structure is favourably supported by the con-stant laying speed of the paver.

5.4.2 Selection criteria

Compaction equipment with jerk-free steering, con-trol, acceleration and deceleration is most suitable for the compaction of asphalt mixtures. Further general demands aim at a completion of the compaction work with the required quality before the critical cooling temperature of the asphalt mixture is reached (see T 3, para. 5.2). All compaction machines and combina-tions capable of meeting these general demands are available. Another differentiation must be made with respect to the application, the areal size and the laying thickness. Normally one must differentiate between the following applications:

- pre-compaction, particularly required in case of insufficient pre-compaction by the paver screed, laying of thick courses and a high temperature of the asphalt mixture, mostly performed with a light roller,

- breakdown compaction with rollers, whereby, in dependence on the properties of the asphalt mixture, the first one or two rolling passes are performed statically and may also be used as pre-rolling,

- finish rolling, as a measure to achieve the required transverse evenness and to close the pores in the surface courses,

- joint rolling, normally separately performed by the roller used for main compaction (T 3, para. 5.5.1, point 8), Fig. 96.

Pre-rolling with a light roller on materialsensitiv shoving Fig. 95

Finish rolling of a surface sourse with a 12 troller with pivot steering Fig. 96


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According to Lit. 13 rollers are recommended for various fields of application and applicational conditi-ons (Tab. 49). Further requirements especially for for light and heavy compaction equipment from BOMAG see Tab. 42 and 43. The use of small compaction machines is most suitable for small areas, in trenches and as additional equipment for special duties.

The ratio between static linear load and drum diameter is an important machine related influencing parameter, which must be observed when compacting asphalt layers. Rollers with identical drum load, but different drum diameters produce different compaction results. Drums with smaller diameters sink deeper into the mixture and cause transverse cracking. In comparison, large drum diameters produce lower horizontal shearing forces, the-reby achieving a better evenness and reducing the dis-placement (shoving) of material (formation of bow waves) and rolling cracks. This influences is accounted for by

means of the so-called Nijboer-factor Nf (Fig. 97 and Lit. 29). For this reason BOMAG compaction rollers are desi-gned with a drum diameter as large as possible and a low Nijboer-factor, to enable perfect compaction even of highly sensitive asphalt mixtures.

5.4.3 Static smooth drum rollers

Static smooth drum rollers compact by the effect of their own weight. In asphalt engineering these rollers are used for pre-compaction, breakdown compaction and finish compaction tasks. By design and weight one differentiates between:(1) Tandem rollers with two drums of identical size and one or two driven axles, weight up to12 t

Influence of the drum diameteron the compaction Fig. 97

Static linear loadNf = Drum diameter

Application Tandem roller Three-wheel roller Vibratory roller Rubber tire roller Combi-roller High breakdown compaction (x) X X (x) (x) Low pre-compaction X - X X X Thick layers X (x) X X (x) (pre-rolling) (heavy) Thin layers on a rigid substrate X (x) - X X Thin layers on a flexible substrate X X - X X Depth effect - - X X (heavy) Evenness X X (x) (x) (x) Closing of pores - - (x) X X Compaction in the lower critical temperature range - X - (x) X Compaction in the upper critical temperature range X - (x) X X Finish rolling X X (x) - -

X = suitable, (x) = conditionally suitable, - = not suitable

Tab. 50: Applications and applicational conditions for the compaction of asphalt by rollers

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(2) Three-wheel rollers with two driven rear drums of identical size and a smaller non-driven front drum, weight 4 to 16 t. Drive axle with differential as a measure to avoid shoving, or with floating axle, which has a positive effect when compacting areas with roof profile.

Large drum diameters enable rolling of smooth sur-faces. However, when used on asphalt mixtures with a high chipping content, pores cannot be completely closed.

The depth effect of static smooth drum rollers is rela-tively low and reaches down to max. 8 cm. With only one driven axle the gradability is limited. Working speed up to 4 km/h.

5.4.4 Pneumatic tired rollers

Pneumatic tired rollers are available with 5 to 11 wheels and smooth tires in the weight range from 5 to 25 t (Fig. 99). They compact the mixture by the dead weight of the machine and by the kneading effect resulting from the deformation of the rolling tires (Fig. 98). The wheels are suspended by a floating axle, ensuring compaction even of small dents or uneven laying thicknesses. The depth effect increases with the wheel load and the tire inflation pressure; it decreases with increasing drive speed. The inflation pressure must be identical in all tires, but should be variable to enable an adaptation of the compaction to varying conditions of paving and substrate: a tire inflation pressure of 5 to 6 bar is commonly used for asphalt compaction.

The main applications are pre-profiling, breakdown compaction of easily compactable asphalt mixtures

and for the sealing of surface courses and base courses. Drive speeds of up to 20 km/h, working speeds of 3 to 4 km/h, or even higher when used for the sealing of surface courses.

The grip between rubber tires and asphalt mixture has a positive effect on the gradability of these machines, enabling these rollers to compact effectively even on very ascending gradients. The hot mixture does not stick to the tires when they are warm (at least 60°C), but at very high temperatures (higher than 160°C) it is harmful for the rubber. Under such conditions the roller must not be left standing on the asphalt layer.

During deployment the pneumatic tired roller normally works in combination with a smooth drum roller or a vibratory roller. The tire inflation pressure depends on the type of mixture under consideration of the required compaction effect, the sealing of pores and the required evenness. With a continuous paving output of the paver best results are achieved by pre-rolling with a smooth drum roller, followed by the compaction with a slow dri-ving pneumatic tired roller with warmed up tires and wit-hout sprinkling of water („hot and dry“). The kneading effect results in a favourable closing of pores, closing even rolling cracks originating from pre-rolling (Fig. 99). For the rolling pattern sufficent overlapping for „ironing out“ tire marks must be taken into consideration.An excessive number of rolling passes at high tempe-rature of the mixture cause a fatting up of the surface with mortar, leaving the surface very slippery.

Areal pressure under the tires (30-80 Mpa) and overlap-ping of front and rear wheels for uniform compaction andironing of tire marks Fig. 98

Use of pneumatic tired rollers for main compaction andfor intensive closing of pores by the kneading effect ofwarm, dry tires Fig. 99


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5.4.5 Vibratory rollers

5.4.5.1 Effectiveness in asphalt compaction

For asphalt compaction vibratory rollers are used in form of hand-guided single drum and double drum vibratory rollers as well as tandem rollers and combi-nation rollers. Due to the interaction of basic machine weight and vibration these machines produce very intensive compaction and depth effects in contrast to dead weight compaction machines. Fundamentals see T 1, para. 1 to 3.

Contrary to other types of rollers, vibratory rollers are able to achieve high compaction effects already after a few passes, whereby the optimal vibration amplitude and the vibration frequency mainly depend on the type of asphalt mixture and the laying thickness. According to general experience surface courses are compacted with low amplitudes and relatively high frequencies, whereas low frequency vibrations and high amplitudes are recommended for thick layers. In order to achieve a smooth surface the finish rolling pass is best perfor-med without vibration.

Large drum diameters are particularly favourable for the high level of evenness that can be achieved with vibratory rollers. At standstill the vibration must be switched off, in order to avoid the formation of trans-verse depressions.

The recommended working speeds for practical appli-cations are 2.5 to 4 km/h for thin layers and 1.5 to 2.5 km/h for thick layers.

A too high number of rolling passes or the use of too heavy rollers must be avoided, especially on thin layers, since this may cause structural disturbances with longitudinal cracks and a poor bond of layers. At high temperatures of the asphalt mixture this effect may even cause the mortar to move up, leaving a slip-pery surface. On thin surface courses or layers on a rigid substrate there is a risk of crushing particles, loosening of layer bond and structural disturbances with cracking. These disadvantages can be avoided by compaction without vibration or by using the directed vibration system BOMAG VARIOMATIC or oscillating vibration systems; see T 3, para. 5.4.6 and. T 1, para. 2.1.4.

5.4.5.2 Hand-guided vibratory rollers

A differentiation is made between the following machine types:

(1) Vibratory rollers with only one drum are small com-pactors steered via a steering rod, which is adjustable in height. The drum is connected to the upper part of the machine via vibration isolating rubber buffers.

(2) Steering rod guided vibratory rollers (Fig. 100 and 101) with two drums of identical size arranged close to each other in line are equipped with exciter shafts and with mechanical or hydrostatic travel and vibration drives; machines with all-drum drive, low centre of gra-vity, hydrostatic steering and parted frame with articu-lated joint in particular are characterised by favourable traction and manoeuvrability .

Steering rod guided vibratory rollerswith two drums Fig. 100

Usw of a steering rod guided single drum rollerfor secondary asphalt work Fig. 101

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5.4.5.3 Tandem vibratory rollers

See T 1, para. 3.4 with illustrations as well as Fig. 102 and 104

This type of roller is equipped with two drums of iden-tical size, each fitted with an exciter shaft (Fig. 102 and 104), and is characterised by the following technolo-gical advantages for asphalt compaction: hydrostatic drives for travel and vibration system powered by an air cooled diesel engine, single lever operation and infinite travel speed control for jerk-free starting, acce-leration and deceleration, hydrostatically controlled articulated steering for highest manoeuvrability.

An automatic vibration feature shuts the vibration down when stopping the roller or when reversing the travel direction, so that the vibration will only continue for a short moment, whereby the formation of surface depressions and shoving of material is avoided.

Heavy tandem rollers are designed for medium to large scale sites: Working widths between 1.5 and 1.8 m or even 2.13 m for the biggest machines. The static linear loads range from 20 to 30 kg/cm.

These rollers generally have two vibrating drums with the possibility to choose from two amplitudes and two fre-quencies, to enable an adaptation of the machine power to various types of material and paving thicknesses.

Two different types of steering are normally available, steering via an articulated joint or pivot steering. Both variants have advantages for certain compaction and movement operation (Fig. 103a and103b).

If rollers with a large drum width are used in tight curves, the rigid drum can cause cracking and defor-mation in the asphalt layer. This is caused by the fact, that the track length of the outer side is longer than the track length for the inner radius. This problem is by-passed by using so-called split drums. However, the design of such a split drum is quite complicated, because for an uniform vibration and highest possible drive power two drive motors and two eccentrics are required (Fig. 105).

Tandem vibratory roller Fig. 102

Single and double pivot steering with andwithout crabwalk Fig. 103b

Crabwalk and articulated steering Fig. 103a


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5.4.5.4 Combination rollers

The combination roller is a combination of a pneuma-tic tired roller and a vibratory roller in the weight range between 2 and 18 t. One axle of the combination roller carries a smooth drum, whereas the other axle is fitted with smooth tires (Fig. 106).

These machines also use air cooled diesel engines as power source for the hydrostatic travel and vibra-tion drives. The rubber tires are driven in pairs by two hydraulic motors, ensuring perfect adaptation of the left and right hand wheel pairs to the different rolling speeds when driving around curves. Single lever ope-ration, hydrostatic power steering as well as automatic vibration enable simple and safe operation of the large combination rollers.

Similar to the pneumatic tired rollers, these machines can also be beneficially used for the „hot and dry“-method. It must, however, been taken into consideration, that the combination rollers have a lower wheel load. No attempt should be made to compensate this lower wheel load by a higher tire inflation pressure, because the tires may then pick up material. The tires should be arranged in such a way, that the gaps between the tires are smal-ler than the width of the tires, so that any remaining tire marks can be „ironed“ by offsetting the machine laterally for the following pass.

Tandem roller with split drum Fig. 104

Combination roller with split drumand four smooth tires Fig. 106

Influence of the split drum on the distributionof strain on an articulated roller Fig. 105

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Combination rollers are mainly used for compaction work on small areas and on steep gradients, whereby an effective compaction is only possible with warmed up tires. When compacting thin layers and under cold weather conditions it is necessary to use an oil emul-sion as a separating agent for the tires. The steel drum must be sprayed with water to prevent material from sticking to the drum.

5.4.5.5 Plates and tampers

Vibratory plates and tampers are used for the com-paction of asphalt mixtures in areas which cannot be accessed with rollers, as well as for minor repair work. These plates and tampers are available in different designs and various weights; see also T 1, para. 3.1 and 3.2 as well as Fig. 107 and 108. Machines that can be adjusted to a low amplitude and a high fre-quency are particularly suitable.

Use of vibratory tampers Fig. 107

Use of vibratory platesfor small work areas Fig. 108

5.4.6 Applicational advantages of the directed vibration system BOMAG VARIOMATIC

The latest development of the directed vibration system BOMAG VARIOMATIC with all its applicational advantages has already been described in T 1, para. 2.1.4; see also Lit. 24 to 28.

The VARIOMATIC system helps the user to improve output and quality to a remarkable extent and releases the roller operator from critical application related deci-sions. The applicational advantages for asphalt com-paction can be summarised as follows:

- universal use on surface, binder and base courses with intensive and uniform compaction

- no particle size reduction during compaction of thin layers as a result of the automatic change-over to horizontal vibration (comparable with oscillating compaction machines)

- laying and compaction of thin layers without loosening or subsequent compaction of the underlaying strata by using horizontal vibration (of advantage when laying hot on warm)

- when complying with the fundamental requirements for asphalt compaction, as mentioned in para. T 3, 5.5, the formation of bow-waves, shoving of the asphalt and cracking is almost completely avoided, because the asphalt is not pressed forward, but pulled under the drum

- particularly favourable smootheness of the surface, because the directed vibrations are automatically adapted to the working direction of the roller

- excellent performance when rolling joints (beneficial when rolling hot on cold).

Another applicational advantage of the VARIOMATIC system is the use in urban areas and on bridges, where excessive vibrations of the environment must be avo-ided. Measurements reveal that the vibration load on nearby buildings can be substantially reduced by pre-selecting the vibration; see Fig. 5 in T 1, para. 1.4.


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5.4.7 List of recommendations for the use of BOMAG vibratory rollers

Figures 109, 110 and Tab. 50 contain lists of recom-mendations for the use of vibratory rollers in asphalt compaction, for the selection of rollers in dependence on mat thickness and laying conditions as well as for the required number of rolling passes for tandem rol-lers in asphalt compaction.

Recommendations for the use of vibratory rollers for asphalt compaction Fig. 109

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Selection of BOMAG vibratory rollers depending on mat thickness of asphalt courses and laying conditions Fig. 110


122

Tab. 50: Recommendations for the number of rolling passes for BOMAG tandem vibratory rollers used in asphalt compaction

5.5 Basic rules of rolling technique (Lit. 27, 37 and leaflet on compaction of asphalt)

5.5.1 Rolling pattern

Intensive and uniform compaction requires an uniform distribution of rolling tracks and rolling passes over the entire paving area. With a large paving width the paral-lel tracks must be compacted with the same types of rollers. The following basic rules are based on practical experience:

(1) Position of the roller to the paver

The driven drums or driven wheels (e.g. combination rollers) should be positioned towards the paver, so that the non-driven drums and wheels transfer the shearing forces into the asphalt mixture, that they do not shove the material and create cracks (Fig. 111). Rolling must generally be performed smooth and wit-hout any jerks. Fig. 112 shows the rolling technique behind the paver. For compaction on steep gradients see point (7).

(2) Overlapping of rolling tracks

Parallel rolling tracks must neither have any uncom-pacted nor any overcompacted strips. The overlapping must be determined with greatest care; normally this overlap should be approx. 10 cm.

(3) Reversing the travel direction

Once work on a compaction track is finished the roller must return on the same track all the way back to the already cooled down area. There the machine can be laterally displaced for the next track. The machine must not perform a U-turn on a soft or hot asphalt mixture, since this will cause shovingor loosening of material. The machine must also not be stopped on a hot mixture. When reversing the travel direction the machine must roll out moothely before it is reversed without any jerks. Here machines with torque conver-ter and hydraulic travel hydraulics are of advantage. On vibratory rollers the vibration must be switched off in due time before reaching the reversing point, so that it comes to a halt before reversing the machine.

(4) Crossfalls

For the stability of a pavement with crossfall it is impor-tant to start rolling at the lowest edge and move across to the highest edge in the middle.

Thickn. of asphalt Number of vibration passes for various

course d (cm) tandem vibratory rollers

3 t 6 t 9 t

2 2 – 4 1 – 2 (L) 1 – 2 (L)

4 4 – 6 2 – 4 (L) 2 – 4 (L)

6 4 – 8 4 – 6 (L) 2 – 4 (L)

10 6 – 8 4 – 8 (L, H) 4 – 6 (L, H)

14 - 6 – 8 (H) 4 – 6 (H)

18 - 6 – 8 (H) 4 – 8 (H)

Stone mastic d = 2 1-2 (L) + stat. pass 1-2 (L) + stat. pass

d = 4 4-6 (L) + stat. pass 4-6 (L) + stat. pass

Drain.asphalt d = 4 1-2 (L) + stat. pass 1-2 (L) + stat. pass

L = low amplitude; H = high amplitude; Assumption: compaction temperature > 100°C3 t = Machines with one amplitude only

Influence of the position of the driven drum to the laying direction and shoving of asphalt mixture Fig. 111

Laying direction

Wrong:Non-driven wheel at front

Correct:Driven wheel at front

Part 3

123

Presentation of rolling patterns behind a paver

(5) Unsupported edges, curbstones

Solid curbstones avoid that mixture is pressed out at the sides. On unsupported edges special attachments on the paver screed or on the roller can prevent pres-sing out of material. They also have a positive effect on the compaction of such edges.

If no curbstones or other means are available it is good practice to roll the first pass approx. 30 cm away from the edge. The outer strip should then be subse-quently compacted after the mixture has stabilised by cooling (Fig. 112b).

(6) Rolling in curves

When rolling in curves compaction shall be started on the inner side (Fig. 113). The rolling pattern in curves depends on the curve radius, the sensitivity of the asphalt mixture against displacement and shoving as well as on the type of compaction machine. The tighter the curve, the more critical the compaction procedure, because in a curve the roller will introduce transverse shearing forces into the asphalt layer, whereby the mixture is dilatantly deformed along the outer radius of the roller track and contracted along the inner radius. This effect is most significant when using rollers with non-split steel drum and a large distance between the drums.

However, the use of vibratory rollers with split drums considerably reduces the risk of shoving and crak-king.

As an alternative solution the rolling pattern may be changed. Compaction should then be started with a two tangetial pre-compaction passes instead of rolling curves.

Rolling pattern with curbstone Fig. 112a

Rolling pattern without curbstone: Outer stripto be compacted last after stabilisation bycooling Fig. 112b

Rolling pattern behind two paverswith curbstone Fig. 112c


124

(7) Compaction on ascending gradients

On ascending gradients the working direction of the roller is of utmost importance, because the required higher tractive power of the machine introduces shea-ring forces into the asphalt layers. For this reason, on rollers with a non-driven drum or on combination rollers the driven drum or driven rubber wheels shall always follow the non-driven drum, even if the first passes have to be performed downhill (Fig. 114).

Rolling pattern for the compactionin curves Fig. 113

Position of the driven drum or thewheels on ascending gradients Fig. 114

(8) Longitudinal, transverse and connecting joints

For the rolling of longitudinal and transverse joints as well as connecting joints between freshly laid and existing mixture certain preparations are required: cleaning, treatment with sealing asphalt sprays or hea-ting of these areas during laying.

Longitudinal joints can be rolled using various methods, whereby the VARIOMATIC rollers with their automatic vibration mode are of particular advantage.

a) Start from the cold side (Fig. 115a): first pass stati-cally without the machine jumping and with only 10 to 20 cm overlap to the fresh mix. Then continue rolling of the fresh asphalt mixture, starting from the outside.

Part 3

125

b) Start from the side of the freshly laid asphalt mix-ture (Fig. 115b): Rolling, for instance, with vibration starting from outside towards inside with an approx. 10 to 20 cm overlap on the inside track. Also in this case the roller must not jump.

Transverse joints between an old and a new asphalt course must be rolled under a right angle to the laying direction (Fig. 115c). At the beginning the roller shall only cover 10 to 20 cm of the new hot layer. For the next pass the overlap is then increased, before chan-ging to rolling in laying direction. Alternatively it may be of advantage to use an additional small roller for this special job or to start rolling under an oblique angle to the transverse joint.

5.5.2 Monitoring of quality influences

Thorough monitoring of the laying and rolling process as well as the compliance with the compaction rules described in para. 5.5.1 is an essential element of self-monitoring and quality control. This will help to detect and rectify quality deficiencies in due time:

(1) Rolling cracks

Transverse cracking may be caused by a number of reasons, such as incorrect position of the roller to the paver, the use of too heavy rollers or insufficient pre-compaction, the too late start of compaction when laying of thick layers, sudden cooling (weather, cold drums, too much sprinkling water), shoving of asphalt mixture on the substrate, on ascending gradients especially on thick courses or sandy mixtures with insufficient binder.

These cracks mostly reach to a depth of only a few millimetres. They will be bonded when rolling the next hot layer, during subsequent compaction with a pneu-matic tired roller or when sealing with a tack coat.

Compaction of transverse joints Fig. 115c

Rolling of joints starting from outsideon the freshly laid asphalt mixture Fig. 115b

Rolling of joints, starting fromthe cold side Fig. 115a


126

Longitudinal cracking is caused by inhomogeneities or deficiencies in the substrate or even by shearing forces in the asphalt mixture caused by the effect of heavy rollers. In these cases it may be necessary to roll the first compacting pass with reduced compaction energy (low amplitude or statically) in order to gain stability, so that the roller can roll without crushing the material.

(2) Transverse unevenness

Transverse unevenness occurs, for example, when the roller shoves the asphalt mixture, if it is stopped on hot material and sinks in, if it is too heavy or has a too small drum diameter, if rolling tracks remain because of non-compliance with the rolling pattern or if the travel direction was reversed on hot asphalt.

If the machine shoves the asphalt mixture like a bow wave or if it sinks in, the machine or operating mode is unsuitable for the job, the mixture is too hot or the layer has not been sufficiently pre-compacted. Another reason may be an insufficient bond between layers or an insufficient adhesion between asphalt layer and the bituminous substrate, e.g. caused by wetness, dirt or excessive spraying, e.g. of a tack coat.

(3) Surface structure

Smoothness and gloss on the surface are indicators for a fattening up of mortar, caused e.g. by vibration, suction by rubber tires. The grip of the surface can be enhanced by interrupting the rolling process until a slightly lower temperature is reached, by changing from vibratory to static rolling or by reducing the number of passes.

(4) Excessive number of rolling passes

The number of passes required for a certain compac-tion work may vary strongly. They depend on a vast variety of factors, such as the compactibility of the asphalt mixture, laying thickness, stability of the sub-strate, pre-compaction by the paver, temperature of the asphalt mixture, type and weight of rollers, rolling speed, weather.

Even though no standard values are available and own experiences with the machines in dependence on mixture and laying conditions must be used or trial compactions with density measurements must be per-formed, empirical reference values, as specified in paragraphs T 3, 5.3 and 5.4.7 as well as in Tab 50, do exist.

By experience, 8 to 12 passes with static rollers and pneumatic tired rollers and 4 to 8 passes with tandem vibratory rollers are required to achieve an intensive or required compaction. Combination rollers have a simi-lar effect as tandem vibratory rollers.

With pneumatic tired rollers there is a risk that mortar will fat up to the surface and reduce the grip when rol-ling too many passes at high temperature, especially on mortar enriched and dense asphalt mixtures.

When using vibratory rollers, a too high number of passes with vibration can cause loosening of material and disturbances in the structure. This applies mainly for thin and already cooled down courses. In order to avoid loosening and fattening up of mortar to the sur-face, thin asphalt courses (thinner than 10 cm) shall only be rolled with low amplitude.

Pneumatic tired rollers should not be used on open graded asphalts with a high chipping content (e.g. stone mastic asphalt, porous asphalt), because the pores in the surface would then be sealed and the pro-portion of air voids in the surface zone reduced.

For vibratory rollers the number of passes with vibra-tion must remain restricted to two, because the topical friction and transfer of forces may cause crushing of particles.

For asphalts with a high chipping content and for open graded asphalts heavy static rollers are most suitable.

Part 3

127

(5) Picking up of hot asphalt mixture

During the compaction of asphalt mixtures in practice the picking up of hot asphalt mixture is counteracted by spraying the steel drums with water and the rubber tires with a bituminous emulsion as separating agent.

When the water contacts the hot mixture it is evapo-rised and extracts heat from the mixture. In extreme cases the surface of the asphalt course will become porous and susceptible for wear. The steel drums must therefore not be sprayed with too much water (rubber scrapers, relaxation agents will help). Modern machines are therefore equipped with interval sprink-ler systems with a reduced water consumption and a longer water capacity.

On pneumatic tired rollers the hot mixture will not stick if the tires are hot and dry. Spraying of the tires with an emulsion consisting of a separating oil and water is therefore only necessary, until the tires have reached a temperature of at least 60°C. However, this is also necessary after the machine has been stopped. The tires can also be warmed up by initial slow driving or by using an infrared radiator.


128

129

Appendix A 1 Conversion Tables

Length

Millimeter [mm]Centimeter [cm]Meter [m]Kilometre [km]Inch [in]Foot [ft]Yard [yd]Mile english [mile]1 mm = 0,03937 in1 cm = 10 mm = 0,3937 in = 0,03281 ft = 0,01094 yd1 m = 100 cm = 39,37 in = 3,281 ft = 1,094 yd1 km = 1000 m = 39370 in = 3281 ft = 1094 yd = 0,6214 mile1 in = 25,4 mm = 254 cm = 0,08333 ft = 0,02778 yd1 ft = 30,48 cm = 0,3048 m = 12 in = 0,3333 yd1 yd = 91,44 cm = 0,9144 m = 36 in = 3 ft1 mile = 1609 m = 1,609 km

Area

Square centimeter [cm²]Square meter [m²]Square inches [sqin]Square feet [sqft]Square yards [sqyd]1 cm² = 0,155 sqin1 m² = 1 . 104 cm²

= 1555 sqin = 10,76 sqft = 1,196 sqyd1 sqin = 6,452 cm²1 sqft = 929 cm² = 0,0929 m² = 144 sqin = 0,1111 sqyd1 sqyd = 8361 cm² = 0,8361 m² = 1296 sqin = 9 sqft

Volumes

Cubic centimeter [cm³]Cubic meter [m³]Cubic inches [cuin]Cubic feet [cuft]Cubic yards [cuyd]

1 cm³ = 0,06102 cuin1 m³ = 1 . 106 cm³ = 61023 cuin = 35,32 cuft = 1,307 cuyd1 cuin = 16,39 cm³1 cuft = 28316 cm³ = 0,0283 m³ = 1728 cuin = 0,037 cuyd1 cuyd = 0,7646 m³ = 27 cuftLiter [l]Gallons (US) [gal]Pints (US) [pint]

1 l = 100 cm³ = 1,7605 pint = 0,2642 gal1 pint = 47,3 cm³ = 0,473 m³ = 0,125 gal1 gal = 378,5 cm³ = 8 pint

130

Mass

Gram [g]Kilogram [kg]Ton [t]Ounce [oz]Pound [lb]Ton short [tshort]Ton long [tlong]1 g = 0,357 oz1 kg = 1000 g = 35,27 oz = 2,205 lb1 t = 1000 kg = 2205 lb1 oz = 28,35 g = 0,0625 lb1 lb = 453,6 g = 0,4536 kg = 16 oz1 tshort = 907,2 kg = 0,9072 t1 tlong = 1016 kg = 1,016 t

Force

Newton [N]Kilonewton [kN]Weight [kgf], [kp], [lbf]

1 kgf = 1 kp = 9,81 N = 2,205 lbf1 N = 0,102 kp = 0,225 lbf1 kN = 1000 N = 101,9 kp = 224,8 lbf

Pressure

1 N/m² = 1 Pa = 1 . 10-5 bar = 1,02 . 10-5 kp/cm²1 N/mm² = 1 . 106 Pa

= 10 bar = 10,2 kp/cm²1 bar = 1 . 105 Pa = 14,399 lb/sqin1 lb/sqft = 47,892 Pa = 143,989 lb/sqin1 lb/sqin = 1 psi = 6894,76 Pa

Energy

Joule [J]Watt [W]Kilowatt [kW]Brit. Ther. Unit [BTU]Kilocalories [kcal]1 J = 1 Ws = 0,7376 ftlb1 kWh = 3,6 . 106 J = 860 kcal1 BTU = 1,054 kJ1 kcal = 4187 J

Power

Horsepower [hp]1 W = 1 J/s1 kW = 1000 W = 1,341 hp = 0,239 kcal/s1 kcal/s = 5,614 hp = 4,187 kW1 hp = 7457 W = 0,1782 kcal/s

Temperature

Celsius [°C]Fahrenheit [°F]

from [°C] to [°F] ð (°C x 9/5) + 32from [°F] to [°C] ð (°F - 32) x 5/9

Appendix A 1 Conversion Tables

131

e Void index Void volume, relating to the solids volume n γs (1+w) γs - γd e = = -1 = 1-n γ γd min e Void index at densest beddiing max e Void index at loosest bedding n Void proportion Void volume relating to the total volume e γ γs - γd n = nw + na = = -1 = 1+e (1+w) . γs γs

nw - Proportion of water filled voids nw = w . γs na - Proportion of air filled voidsmin n Void proportion at densest bedding max n Void proportion at loosest bedding na Air proportion Volume proportion of air filled voids on the total volume γd na = 1 – w • γd – γs D Bedding density max n - n D = max n - min n

ID Related bedding density max e - e ID = max e - min e

γ Volume weight of moist soil 1+w γ = γd (1+w) = (1-n) • (1+w) • γs = • γs

1+e γl Volume weight of soil under γs - γw buoyancy γ l = (1-n) • (γs - γw) = 1+e γd Dry volume weight 1 γd = (1-n) • γs = • γs

1+e γr Volume weight of water saturated soil γs + e • γw γr = (1-n) • γs + n • γw = 1+e γs Particle volume weight Solid mass, relating to the solids volumeρ Density of moist soil analogue γρl Density of soil under buoyancy analogue γ lρd Dry density analogue γd

ρPr Proctor density maximum dry density in Proctor test ρd

Dpr Degree of compaction Dpr = ρPr

ρr Density of water saturated soil analogue γr

ρs Particle density analogue γs

wA Water content Mass ratio of water to the dry solid matterwPr optimal water content Water content, assigned to the maximum dry density in the Proctor testSr Saturation index Volume index for water filled voids on the total proportion of voids n nw w • γs Sr = = n n

Appendix A 2 Compaction Parameters (Soil)

132

133

Appendix A 2 Conversion of Compaction Parameters

Spe

cifie

d M

agni

tude

s S

peci

fied

Mag

nitu

des

R

equi

red

ρ s a

nd ρ

w*

ρ s and

ρw*

M

agni

tude

s w

= w

ges

Sr =

1;n

a = 0

w

i na =

n-n

w

wi S

r < 1

W

ater

con

tent

w

(sat

urat

ed s

oil)

w

W

ater

con

tent

W

(par

tly s

atur

ated

-

w

w

-

soil)

Void

con

tent

n

Vo

id in

dex

e

D

ensi

ty

ρ r (s

atur

ated

soi

l)

Den

sity

ρ

(par

tly s

atur

ated

so

il)

D

ry d

ensi

ty

of th

e so

il

ρ d

S

atur

atio

n

inde

x

Sr

Par

ticle

den

sity

ρ s*

*

*In

gene

ral ρ

w c

an b

e se

t to

1,0

g/cm

3

**ρ

r ; ρ

d or

ρ m

ust b

e kn

own

inst

ead

of ρ

s

n (nw)

e (ew)

ρ rρ (w

)ρ d(w

)

na .

(w . ρ

s + ρ

w)

w +

(1-n

a) .

ρ s

w Sr

nw

ρ w

.

n-1

ρ

s

ρw

e .

ρs

ρs -

ρr

ρw

.

ρr -

ρw

ρ s

ρ

w

ρw

(1

+w).

-

ρ

ρ s

ρ

w

ρw

-

ρd

ρ s

nw

ρ w

.

1-n

ρ

s

ρ w

e

w .

ρ s

S

r . (ρ

s - ρ

) ρ w

.

ρ

- ρr . ρ w

ρ s

ρw

ρw

S

r .

-

ρ

d ρ

s

(

)

w

. ρ s

w

. ρ s +

ρw

w

. ρ s +

na .

ρw

w

. ρ s +

ρw

w

. ρ s

w

. ρ s +

Sr . ρ

wn

e

1 +

e

ρ s -

ρr

ρ s - ρ

w

ρ1

-

(1

+ w

) . ρ

s

ρd

1 -

ρs

ρs

w .

ρw

w

. ρ s +

na .

ρw

ρ w

. (1

- n a)

w

ρ

s

.

Sr

ρ

w

n

1 - n

e

ρ s - ρ

r

ρ s -

ρw

ρ

s

(1

+w).

-

1

ρ

ρ

s

- 1

ρ

d

(1

+ w

) . ρ

s . ρ

w

w .

ρ s + ρ

w

(S

r + w

) . ρ

s .

ρ w

w

. ρ

s +

Sr .

ρ w

(1 -

n) .

ρs +

n .

ρ w

ρs +

e .

ρ w

1 +

eρ r

ρ

ρ w

ρ w

+

1

-

1 +

w

ρ

s

(

)

ρw

ρ w +

ρd

1-

ρs

( )

-

(

1-n a)

. ρs. ρ

w

(1+w

)

w .

ρ s + ρ

w

Sr . ρ

s . ρ

w

(1+w

)

w .

ρ s + S

r . ρw

(1 -

n) .

ρs +

n w .

ρw

ρ s +

ew .

ρ w

1

+ e

-ρ

(1 +

w) ρ

d

ρ s . ρ

w

w

. ρ s +

ρw

(1

- n a)

. ρ

s .

ρ w

w .

ρs +

ρ w

(1 -

n) ρ

s

ρ

s

1 +

e

ρr -

ρw

.

ρs

ρs -

ρw

ρ

1 +

wρ d

1

(1 -

n a) .

w .

ρ s

w .

ρs +

n a .

ρ w

S

r . ρs . ρ

w

w .

ρ s + S

r . ρw

w

wge

s

n w

n

e w

e

1

w .

ρ . ρ

s

ρw [(

1 +

w) .

ρs

- ρ]

w .

ρ d + ρ

s

ρ w . (

ρ s - ρ

d)

ρr .

ρw

ρ

w -

w (ρ

r + ρ

w)

ρ . ρ

w

(1+w

). (1-

n a)-ρ

w-w

. ρ

Sr . ρ

. ρw

(1+w

) . ρ

s - w

. ρ

ρ

- nw .

ρ w

1

- n

(1 +

e) .

ρ -

e w .

ρw

ρd .

ρw

ρ d + ρ

w -

ρ r)

ρ .

ρ w

ρ -

(1 +

w). (

ρ r - ρ

w)

ρd .

ρw

ρw -

w . ρ

d

(w +

w) .

(1 +

na)

. ρ

s .

ρ w

+

w

. ρ s +

ρw

na .

ρw

134

Appendix A 3 Properties of Rock

Roc

k

B

ulk

dens

ity

The

or. d

ensi

ty

Por

osity

Wat

er a

bsor

ptio

n

Tens

ile

She

arin

g C

ompr

essi

on

DIN

521

02

DIN

521

02

DIN

521

02

DIN

521

02

st

reng

th

stre

ngth

st

reng

th

dry

cond

ition

D

IN 5

2102

t/m3

t/m3

%

Mas

s-%

Vo

l.-%

N

/mm

2 N

/mm

2 N

/mm

2

Plu

toni

c ro

ckG

rani

te, s

yeni

te

2,

60 -

2,8

0 2,

62 -

2,8

5 0,

4 -

1,5

0,2

- 0,

5 0,

4 -

1,4

4 -

7 5

- 8

160

- 24

0di

orite

, gab

bro

2,

70 -

3,0

0 2,

85 -

3,0

5 0,

5 -

1,2

0,2

- 0,

4 0,

5 -

1,2

5 -

8 4

-8

170

- 30

0

Volc

anic

roc

kQ

uart

z po

rphy

ry.

porp

hyrit

e, a

ndes

ite

2,

50 -

2,8

0 2,

58 -

2,8

3 0,

4 -

1,8

0,2

- 0,

7 0,

4 -

1,8

5 -

11

5 -

12

180

- 30

0ba

salt

2,85

- 3

,05

3,00

- 3

,15

0,2

- 0,

9 0,

1 -

0,3

0,2

- 0,

8 6

- 12

5

- 13

25

0 -

400

basa

ltic

lava

2,

20 -

2,3

5 3,

00 -

3,1

5 20

- 2

5 4

- 10

9

- 24

-

- 80

- 1

50di

abas

e

2,

75 -

2,9

5 2,

85 -

2,9

5 0,

3 -

1,1

0,1

- 0,

4 0,

3 -

1,0

6 -

10

6 -

10

180

- 25

0

Sed

imen

tary

roc

k

Qua

rtzi

fero

us r

ock:

ve

in q

uart

z, q

uart

zite

)

15

0 -

300

G

rauw

acke

)

2,60

- 2

,65

2,64

- 2

,68

0,4

- 0,

2 0,

2 -

0,5

0,4

- 1,

3

12

0 -

200

qu

artz

ifero

us s

and-

)

st

one

ot

her

quar

tzife

rous

2,00

- 2

,65

2,64

- 2

,72

0,5

- 25

0,

2 -

9 0,

5 -

25

30 -

180

sa

ndst

one

Lim

esto

ne:

D

ense

lim

e, d

olom

ite

2,

65 -

2,8

5 2,

70 -

2,9

0 0,

5 -

0,6

0,2

- 0,

6 0,

4 -

1,8

3 -

6 3

- 7

80 -

180

ot

her

limes

tone

lim

e co

nglo

mer

ate

1,

70 -

2,6

0 2,

70 -

2,7

4 0,

5 -

30

0,2

- 10

0,

5 -

25

20 -

90

tra

vert

ine

2,40

- 2

,50

2,69

- 2

,72

5 -

12

2 -

5 4

- 10

2

- 5

2 -

5 20

- 6

0

Volc

anic

tuff

1,

80 -

2,0

0 2,

62 -

2,7

5 20

- 3

0 6

- 15

12

- 3

0 1

- 5

1 -

4 20

- 3

0

Met

amor

phic

roc

k

Gne

iss,

gra

nulit

e

2,65

- 3

,00

2,67

- 3

,05

0,4

- 2,

0 0,

1 -

0,6

0,3

- 1,

8 4

- 7

3 -

7 16

0 -

280

ta

ble

slat

e

2,

70 -

2,8

0 2,

82 -

2,9

0 1,

6 -

2,5

0,5

- 0,

6 1,

4 -

1,8

m

arbl

e

2,

65 -

2,7

5

0,

1 -

0,5

5

- 8

4 -

8

135

Anhang A 4 Normen, Vorschriften, Richtlinien

Part 1:DIN 1311 Vibrations

Sheet 1: Kinematic terms Sheet 2: Simple oscillators Sheet 3: Vibration systems with a finite number of degrees of freedom

DIN 4150 Vibrations in building

Part 1: Prediction of vibration parameters Part 2: Effects on persons in buildings Part 3: Effects on structures

DIN 45669-1 Measurement of vibration immission Part 1: Vibration meters; requirements, verification Part 2: Measuring method

Recommendation of committee 9, subgrade dynamics, of the „Deutschen Gesellschaft für Erd- und Grundbau e.V.“, July 1992, Bautechnik 1992, Heft 9

Part 2:Safety verification and design loads

DIN 1054 Subsoil - verification of the safety of earthworks and foundations

DIN 1055 Design loads for buildings:

Part 1: Stored materials, building materials and structural members, dead load and angle of friction Part 2: Soil characteristics Part 3: Live loads

DIN 1072 Road and foot bridges; design loads

Contract procedure for construction quantities VOB

DIN 1960 Part A: General directions of contract letting for building works

DIN 1961 Part B: General conditions of contract for the execution of building work

DIN 18299 Part C: General technical specifications for building works; general rules for all kinds of building work

DIN 18300 Part C: General technical specifications for building works; earthworks

DIN 18301 Part C: General technical specifications for building works; drilling works

136

Appendix A 4 Standards, Regulations, Guidelines

Metrology

DIN 1319 Fundamentals of metrology

Part 1: Basic terminology Part 2: Terminology relating to the use of measuring instruments Part 3: Evaluation of measurements of a single measurement, measurement uncertainty

Soil examinations

DIN 1080-6 Terms, symbols and units used in Civil Engineering; soil mechanics and foundation engineering

DIN 4020 Geotechnical investigations for civil engineering purposes

DIN 4021 Soil; exporation by excavation and borings; sampling

DIN 4022 Subsoil and groundwater

Part 1: Classification and description of soil and rock; borehole logging of soil and rock not involving continuous core sample recovery Part 2: Designation and description of soil types and rock; stratigraphic representation of borings in rock Part 3: Designation and description of soil types and rock; borehole log for boring in soil (loose rock) by continuous extraction of cores

DIN 4023 Borehole logging; graphical representation of the results

DIN 4094 Soil; exploration by penetration tests

DIN 4096 Subsoil; vane testing; dimensions of apparatus, mode of operation, evaluation

DIN 18121 Soil; investigation and testing - water content

Part 1: Water content, determination by drying in oven Part 2: Determination of water content of soil by rapid methods

DIN 18122 Soil; investigation and testing - consistency limits

Part 1: Consistency limits; determination of liquid limit and plastic limit Part 2: Consistency limits; determination of the shrinkage limit

DIN 18123 Soil; investigation and testing; determination of grain-size distribution

DIN 18124 Soil; investigation and testing; determination of density of solid particles; capillary pycnometer; wide mouth pycnometer

137


DIN 18125 Soil; investigation and testing

Part 1: Determination of density of soil; laboratory tests Part 2: Determination of density of soil; field tests

DIN 18126 Soil; investigation and testing; Determination of density of non-cohesive soils for maximum and minimum compactness

DIN 18127 Soil; investigations and testing; Proctor-test

DIN 18128 Soil; testing procedures and testing equipment; determination of ignition loss

DIN 18129 Soil; investigation and testing; determination of lime content

DIN 18130 Soil; investigation and testing; determination of the coefficient of water permeability; laboratory tests

DIN 18132 Soil; testing procedures and testing equipment; determination of water absorption

DIN 18134 Soil; testing procedures and testing equipment; plate load test

DIN 18136 Soil; investigation and testing; unconfined compression test

DIN 18137 Soil; testing procedures and testing equipment Part 1: Determination of shear strength; concepts and general testing conditions Part 2: Determination of shear strength; triaxial test

DIN 18196 Earth construction; soil classification for civil engineering purposes Technical testing specifications for soil and rock in highway engineering (TP BF-StB)

Soil exploration in highway engineering, FGSV *

Part 1: Guidelines for the description and evaluation of soil conditions Part 2: Guidelines for contract awards for tze evaluation of soil conditions

Leaflet on surface covering dynamic methods for compaction testing in earthwork, FGSV*

Leaflet on the description of rock groups for civil engineering purposes in highway engineering, FGSV*

Leaflet on description of rock for highway engineering, FGSV*

Leaflet on compaction of subsoil and subgrade in highway engineering, FGSV*

Recommendations, DGGT **:No. 1 Monoaxial compression tests on rock specimen. Die Bautechnik 56 (1979), Heft 7 2 Triaxial compression tests on rock specimen. Die Bautechnik 56 (Heft 1979), Heft 7 11 Swelling tests on rock specimen. Die Bautechnik 63 (1986), Heft 3

*Forschungsgesellschaft für Straßen- und Verkehrswesen ** Deutsche Gesellschaft für Geotechnik e.V.

138

Part 3:

Contract procedure for construction quantities VOB

DIN 18317 Part C: General technical specifications for building works; construction works for traffic lines, top layers of asphalt

DIN 1996 P. 1 to20: Testing of bituminous materials for road building and related purposes

DIN EN 12591 Bitumen and bituminous binders; specifications for paving grade bitumen (replaces DIN 1995)

Bitumen and bituminous binders:

DIN EN 1425 Characterization of perceptible properties

DIN EN 1426 Determination of needle penetration

DIN EN 1427 Determination of the softening point – ring and ball method

DIN EN 1431 Determination of recovered binder and oil distillate from bitumen emulsions by distillation

DIN EN 12593 Determination of Fraaß breaking point

DIN EN 12595 Determination of kinematic viscosity

DIN EN 12596 Determination of dynamic viscosity by vacuum capilary

DIN EN 12697 Bituminous mixtures – Test methods for hot mix asphalt Teil 11: Determination of the compatibility between aggregate and bitumen

DIN EN 12697 Bituminous mixtures – Test methods for hot mix asphalt Teil 34: Indention using cube or Marshall specimens

Additional technical contractual conditions and guidelines for base courses in highway engineering (ZTVT-StB 95/98) (German regulation)

Additional technical contractual conditions and guidelines for the construction of asphalt pavements (ZTV Asphalt-StB 2000) (German regulation)

Guidelines for the standardization of pavements in highway and transportation engineering (RstO-StB 86/89) (German regulation)

Additional technical contractual conditions and guidelines for the maintenance of traffic areas - asphalt construc-tion meathods (ZTV BEA-StB 98) (German regulation)

Guidelines for quality assurance of mineral aggregates in highway engineering (RG Min-StB 93), edition1993, FGSV*


139

Technical delivery conditions for mineral aggregates in highway engineering (rock particle fractions and work stones) (TL Min-StB 2000) (German regulation)

Technical delivery conditions for asphalt in highway engineering. Part: Quality assurance (TLG Asphalt-StB 89) (German regulation)

Technical delivery conditions for polymer modified bitumen, Part 1: Ready to use polymer modified bitumen (TL PmB, Part 1) (German regulation)

Technical test instructions for mineral aggregates in highway engineering (TP Min-StB 99) (German regulation)

Leaflet for suitability tests on asphalt, FGSV*

Leaflet for the use of natural asphalt in asphalt applications for highway engineering, FGSV*

Leaflet on compaction of asphalt, FGSV* Part 1: Practice of compaction Part 2: Theory of compaction

Leaflet for indention measurements with the Benkelman-beam, FGSV*

Leaflet on evenness tests, FGSV*

*Forschungsgesellschaft für Straßen- und Verkehrswesen e.V.


140

141

Part 1:

[1] HERTWIG, A.; FRÜH, G; LORENZ, H. (1933): Die Ermittlung der für das Bauwesen wichtigsten Eigenschaften des Bodens durch erzwungene Schwingungen. Veröff. Degebo T.H. Berlin, H. 1. Springer, Berlin

[2] LORENZ, H. (1960): Grundbau-Dynamik, Springer-Verlag, Berlin – Heidelberg – New York

[3] MACHET, J.M. (1976): Interprétation de lèfficacité des compacteurs vibrants. Rapport de recherche No. 59, Laboratoire Central des Ponts et Chaussées, Paris

[4] YOO, T.S.; SELIG, E.T. (1980): New concepts for vibratory compaction of soil. International Confe- rence on Compaction, Paris

[5] HAUPT, W. (1986): Bodendynamik, Grundlagen und Anwendung. F. Viehweg u. Sohn-Verlag

[6] STUDER, J.; ZIEGLER, A. (1986): Bodendynamik. Springer-Verlag, Berlin – Heidelberg – New York – Tokyo

[7] KRÖBER, W. (1988): Untersuchung der dynamischen Vorgänge bei der Vibrationsverdichtung von Böden. Diss. Lehrstuhl und Prüfamt für Grundbau, Bodenmechanik und Felsmechanik der Techni- schen Universität München, Schriftenreihe Heft 11

[8] KRÖBER, W. (1995): Numerische Simulation der Vorgänge bei der Vibrationsverdichtung. Festschrift: Beiträge aus der Geotechnik. Lehrstuhl und Prüfamt für Grundbau, Bodenmechanik und Felsmecha- nik der TU München, Schriftenreihe Heft 21

[9] HUBER, H. (1996): Untersuchungen zur Materialdämpfung in der Bodendynamik. Diss. Lehrstuhl und Prüfamt für Grundbau, Bodenmechanik und Felsmechanik, Technische Universität München, Schrif- tenreihe Heft 23

[10] ANDEREGG, R. (1997): Nichtlineare Schwingungen bei dynamischen Bodenverdichtern. Diss. ETH Nr. 12419, Eidgenössische Technische Hochschule Zürich

LiteratureSelection within the scope of compilation of volume 1

142

Literature

Part 2:

[11] KÜHN, G. (1956): Der gleislose Erdbau. Springer Verlag, Berlin, Göttingen, Heidelberg

[12] MÜLLER, L. (1963): Der Felsbau, 1. Band: Grundlagen, Ferdinand Enke Verlag, Stuttgart

[13] (1976): Handbuch des Straßenbaus. Band 2. Springer Verlag, Berlin – Heidelberg – New York

[14] FLOSS, R.; SIEDECK, P.; VOSS, R. (1968): Verdichtungs- und Verformungseigenschaften grobkörniger, bindiger Mischböden. Bundesanstalt für Straßenwesen, Wissenschaftliche Berichte H. 6. Verlag W. Ernst & Sohn, Berlin – München – Düsseldorf

[15] FLOSS, R. (1970): Vergleich der Verdichtungs- und Verformungseigenschaften unstetiger und steti- ger Kiessande hinsichtlich ihrer Eignung als ungebundenes Schüttmaterial im Straßenbau. Bun- desanstalt für Straßenwesen, Wissenschaftliche Berichte H. 9. Verlag W. Ernst & Sohn, Berlin – München – Düsseldorf

[16] WITTKE, W. (1984): Felsmechanik, Grundlagen für wissenschaftliches Bauen in Fels. Springer Verlag, Berlin – Heidelberg – New York

[17] FLOSS, R. (1985): Dynamische Verdichtungsprüfung bei Erdbauten. Straße und Autobahn 36, Heft 2

[18] FLOSS, R.; REUTHER, A. (1990): Vergleichsuntersuchungen über die Wirkung von vibrierend und oszillierend arbeitender Verdichtungswalze. Lehrstuhl und Prüfamt für Grundbau, Bodenmechanik und Felsmechanik der Technischen Universität München, Schriftenreihe H. 17

[19] Lehrstuhl und Prüfamt für Grundbau, Boden- und Felsmechanik der Technischen Universität München (1991): Dynamische Verdichtungsprüfung bei Erd- und Straßenbauten; Forschungsberichte aus dem Forschungsprogramm des Bundesministers für Verkehr und der Forschungsgesellschaft für Straßen- und Verkehrswesen e.V., Heft 612

[20] FLOSS, R. (1992): Flächendeckende Qualitätskontrolle bei Verdichtungsarbeiten im Erd- und Straßenbau. Proc. 1. Internationales Symposium „Technik und Technologie des Straßenbaus“, BAUMA 1992

[21] FLOSS, R. (1996): Qualitätssicherung im Erdbau – Anwendung der neuen Prüfmethoden gemäß ZTVE-StB 94, Forschungsgesellschaft für Straßen- und Verkehrswesen, Köln, Schriftenreihe der Arbeitsgruppe „Erd- und Grundbau“, Heft 7

143

LiteratureSelection within the scope of compilation of volume 1

[22] ADAM, D. (1996): Flächendeckende Dynamische Verdichtungskontrolle (FDVK) mit Vibrationswalzen. Diss. Institut für Grundbau und Bodenmechanik, Technische Universität Wien

[23] FLOSS, R. (1997): Zusätzliche Technische Vertragsbedingungen und Richtlinien für Erdarbeiten im Straßenbau (ZTVE-StB 94/97). Kommentar mit Kompendium Erd- und Felsbau, Kirschbaum Verlag, Bonn

[24] FLOSS, R.; HENNING, J. (1998): VARIOMATIC. Ein entscheidender Schritt zur Qualitätssicherung im modernen Erd- und Verkehrswegebau. BOMAG Heft BA 049, Boppard; Vortrag Floss, R. 3. Inter- nationales Symposium „Technik und Technologie des Straßenbaus“, BAUMA 1998

[25] KLOUBERT, H.-J. (1999): Anwendungsorientierte Forschung und Entwicklung löst Verdichtungspro- bleme im Erd- und Straßenbau. 28. VDBUM Seminar, Verband der Baumaschinen-Ingenieure und Meister e.V.

[26] KROEBER, W. (1999): VARIOCONTROL und FDVK im Erdbau – schwierige Verdichtungsaufgaben sicher und wirtschaftlich gelöst. 28. VDBUM Seminar, Verband der Baumaschinen-Ingenieure und Meister e.V.

[27] UEBERBACH, O. (1999): The Book of Compaction, Pub. by BOMAG, Boppard

[28] FLOSS, R.; KLOUBERT, H.-J. (2000): Newest Innovations into Soil and Asphalt Compaction Tech- nology. International Workshop on Compaction of Soil, Granulates and Powders, Innsbruck, Febr. 2000, A.A. Balkema-Verlag, Rotterdam

Part 3:

[29] NIJBOER, L. W. (1955): Dynamic Investigations of Road Construction. Shell Bitumen Monograph No. 2

[30] DEMPWOLFF, K.R. (1977): Bemessung bituminöser Befestigungen. Handbuch des Straßenbaus, Band 3, Springer Verlag, Berlin – Heidelberg – New York

[31] HEINEMANN, R. (1972): Mathematische Ansätze zur Berechnung verdichtungsunabhängiger Größen. Bitumen – Teere – Asphalte – Peche 23, 6

[32] SCHMIDT, H. (1977): Bituminöse Bindemittel. Handbuch des Straßenbaus, Band 2, Springer Verlag, Berlin – München – New York

144

[33] FORSCHUNGSGESLLSCHAFT FÜR STRASSEN- UND VERKEHRSWESEN (1987): Arbeitsanlei- tung für die Bestimmung der Verdichtbarkeit von Walzasphalt mit Hilfe des Marshall-Verfahrens

[34] ARAND, W.; RENKEN, P. (1988): Einfluß der Mischdauer und der Verdichtungstemperatur auf die Verdichtbarkeit von Walzasphaltgemischen. Schriftenreihe „Forschung Straßenbau und Straßenverkehrstechnik“ des Bundesministers für Verkehr. Abteilung Straßenbau, Heft 523

[35] HÜNING, P. (1994): Grundsätze für die Zusammensetzung von Asphalten zur Erzielung bestimmter Eigenschaften, Asphalt 5/1994

[36] ARAND, W. (1996): Einfluß von Temperatur und Temperaturrate auf den Verformungswiderstand frisch verlegter Asphaltdeckschichten während Abkühlung und Wiedererwärmung. Asphalt 8/1996

[37] DÜBNER, R.: Einbauen und Verdichten von Asphaltmischgut, ARBIT-Schriftenreihe H. 53

[38] ARAND, W. (1998): Zur Strukturviskosität von Bitumen. Bitumen 60, Heft 3

[39] HALFMANN, U.: Straßenbaustoffe. Handbuch für Straßen- und Verkehrswesen, Teil G, Ausgabe 2001, Otto Elsner Verlagsgesellschaft, Dieburg

[40] LENKER, S.: Befestigungen. Handbuch für Straßen- und Verkehrswesen, Teil H, Ausgabe 2001, Otto Elsner Verlagsgesellschaft, Dieburg

Literature

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146

147

AAASHO – American Association of State Highway Officials ...........................................................38Air void content Asphalt ......................83, 91, 94, 95, 96, 98, 100Air voids (soil) .....................................46, 48, 50, 55Amplitude ....................... 8*, 16*, 17, 18, 21, 79, 120 Anti-sticking agent .......................................119, 127Areal output, compactor ..................................66, 67Articulated steering .......................................26, 117ASC Anti-Spin-Control system .......................28, 31Asphalt base course........................................82, 91Asphalt binder ............................................... 93, 94*Asphalt binder course .....................................82, 83Asphalt concrete................................ 82, 92, 93, 95*Asphalt mastic ................................................93, 98Asphalt surface course ....................................82, 83Asphalt temperature Laying .............................................................93 Rolling................................................... 104, 109 Attachment plates ...........................................29, 45

BBedding modulus...................................................52Bitumen ...........................................................83-88Bitumen emulsion .................................................88Blasting of rock ......................................................60Bulk density (asphalt) .................................100, 102

CCalcareous sandstone ..........................................63Calculation of output........................................66, 67CBR California Bearing Ratio ................. 52*, 55, 56Centrifugal force ....................................16*, 17*, 18*Circular exciter (circular vibrator) ..........................11Combination roller .........................................28, 118Compaction depth ...........................................72, 73Compaction energy .........................................13, 19Compaction of joints ....................................124, 125Compaction output Soil..................................................... 66, 67, 74 Asphalt................................................... 109-112Compaction resistance (asphalt) .................100-104Compaction temperature (asphalt) see asphalt temperature

Compaction water content.........................43, 44, 70Compaction work Soil..................................................... 47, 48, 49 Asphalt ..................................................100, 101Compactness...................................................46, 48 Consistency index .........................36, 39, 51, 55, 56Curvature index ...............................................33, 34

DDeformation modulus .......................................51-56 Static ............................................................. 52* Dynamic ........................................................ 53*Degree of compaction Soil..................................40, 46, 48*, 50, 51, 55 Asphalt ..................................... 83, 94-96, 102*,Depth effect .................19, 29, 76, 76, 115, 117, 118Directed vibrator ..................................11, 13, 14, 75Dolomite ...............................................................57Double vibratory roller ....................................26, 64Drum .......................................................27, 28, 118Drum acceleration .......................................... 13,16*Drum diameter.............................................114, 116Dry density ............................................................46Dynamic stiffness ...........................9, 10, 15, 17, 21

EEnergy transfer .....................................................75Exciter shaft...........................................................11

FFrequency .......................... 16*, 17*, 19, 72, 76, 120Fundamental vibration .............................................7

GGradability of roller ..........................................28, 31Gussasphalt ................................ 82, 83, 92, 93, 97*

HHand-guided vibratory roller ...................25, 26, 116Harmonic vibration ..................................................9

Glossary*Definition, description

148

Hot and dry .................................................115, 118Hydraulic plate ......................................................25

IIgneous rock .........................................................57Indicator diagram ..................................................21Inflation pressure, pneumatic tired roller ............115

JJump operation......................................13, 9, 22, 75

LLayer thickness (lift height) .......................66, 67, 73Limestone..............................................................57Liquid limit .............................................................36Loosening of surface ......................................45, 75

MMarshall-method..................................................102Metamorphic rock..................................................57Mudstone...............................................................62

N

Natural frequency ..............................................8, 22Natural vibration ......................................................8Nijboer factor .......................................................114

OOptimal water content.................. 47*, 43, 49, 50, 70Oscillator .........................................................11, 12Output of compactor ..............................................74 Soil..................................................... 66, 67, 74 Asphalt ...................................................109-112Overcompaction ..............................................75, 13

PPadfoot roller ............................30, 31, 63, 70, 76-78Particle size fraction ..............................................33Penetration (Bitumen) .....................................87, 88Pivot steering.................................................26, 117Plastic limit.............................................................36Plasticity diagram ..................................................35Plasticity index ................................................36, 39Pneumatic tired roller ............................76, 114, 115Polymer modified asphalt .....................................98Polymer modified bitumen ..............................83, 88Pre-compaction ...................................................113Pressure distribution Vibrator ...........................................................12 Oscillator .........................................................12Proctor curves ...........................................47, 48, 50Proctor test ......................................................47, 49Propagation of vibrations.....................9, 10, 29, 119PSV – Polished Stone Value ...........................89, 92

RResilient stiffness ........................................8, 10, 21Resonance vibrations .............................................8Ripping of rock.......................................................60Rock classes .........................................................60Rock of variable strength ......................................62Rolled asphalt................................................83, 101Rolling cracks ..............................................122, 125Rolling passes Soil...........................................20, 66, 67, 77, 79 Asphalt.....................................20, 101, 122, 126Rolling pattern Soil........................................................... 67, 68 Asphalt .................................................122 - 125Rolling speed ..............20, 66, 67, 72, 111, 116, 120

SSandstone ............................................................63Saturation index.........................................44, 46, 48Sedimentary rock ................................................ 57*Seismic wave speed .............................................60Self-regulating system...............................13, 14, 29Shearing strength (soil) ..................................41, 42Siltstone.................................................................62Single drum roller ..................... 28-31, 45, 61, 63-67

Glossary

149

Single wheel vibratory roller ...........................26, 64Slates.....................................................................63Softening point RaB (bitumen) .......................87, 88Soil............................................................................. Engineering properties ....................................40 Compaction properties ...............................48-51Soil classes............................................................39Soil classification ..............................................33-37Soil contact force ..................................10,15, 20, 21 Soil parameters ...............................................41, 42Soil stabilisation (treatment) ...........................43, 71Solid rock ..............................................................61Sprinkler system..................................................127Static axle load ................................................16, 17Static compaction ..........................................75, 126Static linear load.............................. 16*, 72, 76, 120Stiffness ofsubstrate..................10, 11, 17, 21, 45, 79, 116, 117Stone mastic asphalt .............................. 92, 93, 96*Subharmonic vibration.............................................9Surface course ......................................................82Surface protection courses.............................83, 99,Surface treatment ............................................88, 99Surface waves .........................................................9

TTandem roller..............................26-28, 94, 113, 109Towed roller ..........................................................32Traffic load .......................................................82, 92Trial compaction ..............................................68, 69

UUnbalanced mass.......................................... 11, 16*Uniformity index...............................................33, 34Uniform sands .................................................45, 49USC Unified Soil Classification System................ 37

VVARIOCONTROL ................. 14, 15*, 16, 29, 75, 79VARIOMATIC .................. 13, 14*, 91, 116, 119, 124Vibration acceleration ..................................9, 10, 29Vibration exciter.....................................................11Vibration force .......................................................18

Vibration generation ............................................ 17*Vibrating mass.................... 14, 16*, 17*, 21, 72, 120Vibration path ...................................................... 16*Vibration speed..................................................8, 10Vibratory plate ........................................23, 119, 24Vibratory rollers ......... 25-32, 76-79, 94-96, 116-121Vibratory tamper ...........................................23, 119Viscosity (bitumen) ...............................................85Void proportion ...........................................46-51, 54Volcanic rock ....................................................... 57*

Glossary*Definition, description

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