Newly Developed Technologies for Roads and Bridges - Compreehensive Design Example

8/2/2019 Newly Developed Technologies for Roads and Bridges - Compreehensive Design Example

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[Mukabi JN (Ph.D) KEYNOTE LECTURE] Page 1

Newly Developed Technologies for Roads and Bridges: An Example of ComprehensiveDesign and Construction Approach Considering Tropical Geomaterial Characteristics

John MUKABI 1, Kazuyuki GONO 2, Stephen NGARE 3, Francis NYANGAGA 4, Bernard NJOROGE 5,Rikiya HATEKAYAMA 6, Abiy TESFAYE 7, Girma FELEKE 8, Silvester KOTHEKI 9

1Kenstesu Kaihatsu Consultants Ltd. [email protected]/[email protected], 2KajimaCorporation [email protected], 3Ministry of Roads and Public Works. [email protected],4Kenya Roads Board [email protected], 5University of Nairobi [email protected],6Kajima Corporation [email protected], 7European Union [email protected],

8Gibb Africa [email protected], 9Kensetsu Kaihatsu Ltd. [email protected]

Abstract: The use of geomaterials for road construction and geotechnical structures is adefinite prerequisite. However, in most cases, geomaterials are usually deficient or lacking inseveral of the properties necessary for their use as engineering materials. Such cases areaggravated when the engineer encounters problematic soils, which are normally susceptibleto even the slightest of changes in environmental factors such as moisture-suction variations.Moreover, when such materials are adopted for engineering purposes, the roads andgeotechnical structures have a tendency of either deteriorating at an alarming rate and/orfailing altogether.

Furthermore, in developing countries, the Civil Engineer is almost constantly constraineddue to lack of sufficient or necessary financial resources and/or technical capability. Underthese circumstances therefore, it becomes almost imperative that innovative engineeringconcepts and methods are applied to face and resolve such challenges effectively. The

methods must take into account factors such as appropriate technology, investment benefit,cost reduction, maintenance requirements and most of all, reasonable sustainability . In this study, innovative experimental methods and recently derived powerful analytical

tools have been employed to develop several unique methods of enhancing the engineeringproperties of geomaterials, and adopted for design and construction.

1. INTRODUCTIONIn order to minimize anomalies and achieve an appropriate design, it is essential that theaspects and concepts mainly fostering a Value Engineering (VE) based cost-effectiveapproach that is based on research oriented methods are employed.

The proposed Comprehensive Method of Design (CMD) is introduced in this paper by

giving a practical example of a detailed design of a road in Juba, southern Sudan.This paper further cites (refer to Mukabi, 2008KNL This Conference) a wide range of

some of the recently developed analytical tools that can be adopted in providing engineeringsolutions to some of the challenges posed. For example, the existing (distressed) pavementcondition is evaluated by applying non-linear kinematic hardening and Consolidation andShear Stress Ratio (CSSR) concepts with loading conditions, environmental and seasonalfactors as main inputs. The structural soundness of both the composite pavement andindividual layers is then derived by applying the Intensity Factor concept to analyze the rate ofdeterioration of the structural thickness. On the other hand, the qualitative assessment of thedeficiency in the physical properties of the pavement materials with time through the intrusionof fines to the upper pavement layers is made by employing a set of recently proposedempirical formulae. The modulus of deformation parameters, applied in characterizing themode of deformation of the composite pavement, is derived on the basis of linear elastic andpre-failure theories and concepts.
mailto:[email protected],%203Ministrymailto:[email protected],%203Ministrymailto:[email protected],%203Ministrymailto:[email protected],%204Kenyamailto:[email protected],%204Kenyamailto:[email protected],%204Kenyamailto:[email protected],%204Kenyamailto:[email protected],%204Kenyamailto:[email protected],%203Ministry


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2. THE COMPREHENSIVE METHOD OF DESIGNThe Comprehensive Method of Design (CMD) was first proposed at the XXIII (23 rd) WorldRoad Congress held in Paris, France (Mukabi et al, 2007a) and further discussed at the 14 th African Regional Conference held in Yaound, Cameroon (Mukabi et al, 2007c).

This method is depicted in Fig 2.1.

Fig. 2.1 Comprehensive Method of Design

3. SURVEY PROCEDURESS AND TESTING REGIMEThe sampling and Survey procedures are presented in Chapter 2 of the Engineering ReportNo. SST1 of May, 2007, while the conventional and innovative testing regimes are describedin Chapter 3 of the same Report.


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Table 6.1 Comparison of Design Criteria for Physical, Strength and BearingCapacity of Stabilized Materials from Various Sources

Pavement Layer Source UCS(kgf/cm 2)

CBR(%)

PI

SubbaseMaterials TRL 7.5~15 > 70 < 10ASSHTO - - -JRA 10 - < 10KRDM - > 60 < 12This Study(OPMC)

11.3~16.4 209~283 6~12

Base CourseMaterial

TRL G: 15 ~ 30H:30 ~ 60

> 100 < 6

ASSHTO 28~52.5 - -JRA 25~30 - < 9KRDM 18 > 160 < 10This Study(OPMC)

23.9~39.2 391~611 0~6

Notes:a. PI : Plasticity Index, UCS : Unconfined Compression Strength, CBR : California Bearing Ratiob. TRL : Transport Research Laboratory, ASHTO : American Association of State Highway

Officials, JRA : Japan Road Association, KRDM : Kenya Road Design Manual.c. Results from This Study were determined from tests performed on various OPMC Stabilized

Materials under 7 days cure + 7 days Soak Conditionsd. Cement additive percentage Subbase : 4~6%, Base Course : 4~8%.

4. COMPREHENSIVE DATA ANALYSIS AND MATERIALS CHARACTERIZATIONComprehensive data analysis and materials characterization was undertaken, of which theresults, observations and derivations are reported in Chapter 5 of the Engineering Report no.SST1 of May 2007.

The innovative and high-tech analytical tools that were used are defined in Chapter 3 and4 of the same Report.

5. APPLICATION OF TEST RESULTSThe modes describing how the test results and findings were applied are discussed underChapter 6 of the Engineering Report No. SST1 of May 2007.

6. COMPARISON OF STUDY DATA WITH VARIOUS DESIGN CRITERIA(1) Comparison of design criteria from physical, strength and bearing capacity testsIn Chapter 5 comprehensiveand detailed materialscharacterization and dataanalysis was carried out. Inthis section, the data thatwas determined from thevarious tests and analysis iscompared with the designcriteria specified by severalInternational Agencies.

Table 6.1 presents acomparison of the resultsdetermined from this studyand design criteria stipulatedby various Agencies forcritical design parameterssuch as plasticity Index PI, Unconfined Compression Strength (UCS) and California BearingRatio (CBR).

In general, it can be appreciated that the material that was tested under OPMC stabilizationyields design parameters that are well above the criteria stipulated by virtually all theAgencies.

(2) Comparison of applicable specification criteria for stabilized natural gravel anddesign parameters from This Study

Thecomparison ofapplicablespecificationcriteria forstabilizednatural graveland designparametersdeterminedfrom this study

is tabulated inTable 6.2.

Table 6.2 Comparisons of Specification Criteria for Stabilized Natural Gravel andDesign Parameters from This Study

PavementLayer Reference PI PM PP CBR (%)

UCS(kgf.cm 2)

Mr (kgf/cm 2)

SubgradeMaterial

Specification _ 1200 _ _ _ 150~2,500This Study 11~25 306~468 - 81~110 11.3~16.4 174~483

SubbaseMaterials

Specification 3000This Study 6~12 141~282 138~276 209~283 11.3~16.4 2380~6860

Base CourseMaterial

Specification < 6 _ < 45 > 160 _ > 10000This Study 0~6 0~141 0~93 391~611 23.9~39.2 123983~454893

Notes:a. PI : Plasticity Index, PM : Plasticity Modulus, PP : Plasticity Product, CBR : California Bearing

Ratio, UCS : Unconfined Compression Strength, Mr : Resilient Modulus UCS : UnconfinedCompression Strength, CBR : California Bearing Ratio

b. TRL: Transport Research Laboratory, ASHTO: American Association of State Highway Officials,JRA : Japan Road Association, KRDM : Kenya Road Design Manual.c. Results from This Study were determined from tests performed on Optimmully (Mechanically and

chemically) Stabilized Materials under 7 days cure + 7 days Soak Conditionsd. Cement additive percentage Subbase : 4~6%, Base Course4~8%.


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In case it is circumstantially not possible to blend it at source then the material shall beextruded from different location and/or depths within the same source or borrow pit.The engineering properties including mainly the physical, mechanical and strengthshall be tested and confirmed to be within the design and specified criteria prior to usefor construction works.Quality control tests of the materials shall be undertaken accordingly and therequirements shall be adhered to strictly.Further testing and/or soil improvement shall be carried out for materials whoseproperties are on the border line or within the mean value of the Lower and UpperBoundary Limits of the Design Criteria and/or Specifications.

(6) Adopted Design CriteriaThe following standards and/or design criteria are thence mainly adopted in appropriation tothe suitability, relevance and cost-effectiveness for the purposes of the design of the JubaRiver Port Access Road.

1. TRL : Transport Research Laboratory Overseas Road Note 312. Japan Road Association Manual for Asphalt Pavement 19893. Kenya Road Design Manual Part III Materials And Pavement Design for New Roads

1987

7. EVALUATION OF TRAFFIC STRUCTURE AND GROWTH7.1 Evaluation of Existing Traffic VolumeThe traffic volume was analyzed by converting the mixed traffic to equivalent single axleload based on a Traffic Volume Survey carried out for three days for twelve (12) hoursfrom 6.00am to 6.00 pm on weekdays on Thursday and Friday and one day of theweekend Saturday. Considering that estimates of the amount of traffic and itscharacteristics play a primary role in the pavement design and analysis process, effort

was made to obtain the latest traffic data count. A detailed review of the aggregated datawas undertaken.Computation of traffic volume growth rates and cumulative ESAL based on year

2005/2006 Field Interview Survey and Traffic Count Data respectively, is presented inTables 7.1 to 7.4. On the other hand, Table 7.4 presents a comparison of growth in trafficvolume between Nov. 2005 and May 2006. These tables indicate that actual trafficgrowth rate increased to drastically higher levels than the normal. It can be derived fromthese tables that, the traffic volume growth is particularly high for both trucks and tractortrailer trucks.

Table 7.1 Present Traffic Volumes, 2006

Figure 7.1 - Traffic Count Survey Sites

Locat ion Pedestr ian Bicycle Motocycle Passenger

Car

Mini Bus Bus Picup Light

Truck

Medium

Truck

Heavy

Truck/ Trailer

=


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7.2 Traffic ForecastingThe annual growth rate factor (GRf) iscomputed from the equation provided byAASHTO (Guide for Design of PavementStructures)

g

gG

n

Rf

11

(7.2)

where,n = Analysis periodg = Annual Growth Rate inpercentage

The computation results of the growth

rates and cumulative Equivalent SingleAxle Load based on the year 2005/2006 traffic count data are presented in Tables 7.1 to 7.2,while the comparison of growth rates of traffic and cumulative ESAL as well as computation ofthe Intensity of growth factor ( ) is given in Table 7.5 Maximum analysis of the impact ofincreased ESAL is carried out under a separate section. Nevertheless, the significant growthin traffic volume and the corresponding growth rates can obviously be appreciated.

7.3 Traffic Volume Analysis and Determination of Cumulative ESALTable 7.3 Summary of Traffic Count Data For Juba Port Access Road

Source: JICA Study Team (Katahira & Engineers International)

Table 7.4 Computation of Projected Growth Rates and Cumulative ESAL by JICA Studyteam (Katahira & Engineers International)

Notes :

Computation is based on a 2-way flowDesign Period = 20 Remaining Period = 20 years, Terminal Serviceability Index (Pt) = 2.0,Pavement Structural Number (SN) = 5

Day CargoTrucks

TrailerTrucks

Vans Mini-Buses

Buses Sedans Cars MotorBikes

Total Traffic Volume(Thu~Sat, 25~27 May 06)

342 130 336 267 101 312 278 624

Average Rate 114.00 43.33 112.00 89.00 33.67 104.00 92.67 208.00

RoadSection Vehicle Types AADT in 2006

Growth RateFactors Design Traffic ESAL Factor

CumulativeDesign ESA

(x106)

A c c e s s

R o a

d t o

J u

b a

R i v e r

P o r t

Sedan 93 45.76 1,553,323 0.0008 0.002374

Small Buses 101 29.78 1,097,840 0.0122 0.04314

Large Buses 34 41.00 508,810 1.0000 1.073465Cargo Trucks 114 36.79 1,530,832 3.2000 11.517648

Trailer Trucks 44 41.00 658,460 5.7000 15.836766

Total 386 - 5,349,265 - 28.47339

Table 7.2 - Traffic Count Data For Juba PortAccess Road Day of Survey:Thur,25/05/06

Source: JICA Study Team (Katahira & Engineers International)

Time Trucks TrailerTrucks

Vans Mini-Buses

Buses Sedan Cars MotorBike

6:00-6:30 6 0 0 3 0 0 0 36:31-7:00 0 0 0 0 0 1 0 17:01-7:30 1 1 1 1 0 1 1 17:31-8:00 3 4 3 3 0 7 12 38:01-8:30 9 0 1 8 1 2 14 58:31-9:00 4 3 6 4 1 5 7 6

9:01-9:30 13 1 4 8 1 5 14 69:31-10:00 6 10 4 3 1 6 7 8

10:01-10:30 4 1 7 3 2 5 2 1010:31-11:00 6 1 7 4 2 8 5 1411:01-11:30 4 0 3 2 2 3 3 911:31-12:00 2 0 1 1 0 3 1 612:01-12:30 3 0 1 2 0 0 3 812:31-13:00 1 1 2 1 1 3 5 1213:01-13:30 3 4 1 1 1 2 4 1013:31-14:00 7 1 0 1 1 5 6 414:01-14:30 2 7 2 1 1 5 3 814:31-15:00 5 2 9 2 2 6 4 1315:01-15:30 4 1 8 7 0 2 2 1015:31-16:00 5 0 0 2 1 1 3 716:01-16:30 4 0 2 4 0 6 4 516:31-17:00 1 2 2 0 3 417:01-17:30 1 0 5 1 0 2 6 1017:31-18:00 3 0 2 2 0 0 3 8

Total 91 39 71 64 17 78 112 171


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Table 7.5 Comparison of Growth Rates of Traffic and Cumulative ESAL between 2006and 2026

IGf : Intensity of Growth factor is defined asn

iiGf xG

1iESAL100

1 (After Mukabi, 2002c)

7.4 Impact of Increased ESALThe increase in traffic volume has contributed to higher values of cumulative ESAL as can bederived from Tables 7.1 ~ 7.4. The cumulative ESAL was computed from Eq. 7.2, and anexample of the calculation for Trailer Trucks.

The cumulative number of standard axles was computed based on the principle of convertinga mixed traffic stream of different axle loads and axle configurations into a design trafficnumber in the form of an equivalent number of 8.2 tonnes single axle loads summed over a

design period of 20 years The equation adopted for this computation is :-

0

1log11

....365 r r

Pr

viv GGe

G EF d C n N

DL

l

(7.3)where,

N = number of equivalent standard axle repetitionsn iv = initial number of vehicles daily in one directionCv = proportion of commercial vehicles expressed in decimal formG r = annual growth rate expressed in decimal formd l = proportion of vehicles using the design lane as a decimal (dl = 1)P DL = design life for the pavement in yearsEF = axle load equivalency factor expressed as:

EF = (Ls/80) 4.5

where Ls is the load in kN on the single axle considered taking a regional factor of 1.0and Terminal Serviceability Index Pt = 2.0

As an example, for the computation of ESAL of trailer trucks, consider that: -n iv = 22, C v = 1, G r = 0.2, d l = 1, P DL = 20 years and E F = 5.7 then applying Eq.7.3 we obtain,

2.01

12.017.51122365

20

eog x x x x x N

l

= 365x22x5.7x173= 7,918,383

Vehicle

Type

Value Adopted for the Basic Design Current Values Adopted in this Study

AADT

In2006

ProjectedGrowth

Rate up to2026%

ProjectedAADT

in2026

Estimated8.2t

Equivalent

RevisedCumulative

ESALESALx10 6

(in 2006)

ComputedCumulative

ESALESALx10 6

in 2026

PercentageIncrease/

Decrease in

ESAL in relatioto BD Values(G)

2026 2026

Sedan 93 20 145 Nil - - - -Bus

(small)101 20 158 Nil - - - -

Bus(large)

34 20 53 1 0.00689 0.537 77.9 41.8

CargoTruck

114 20 178 3.2 0.0739 5.759 7.8 449.2

TrailerTruck

44 20 69 5.7 0.0508 7.918 155.9 1,234.4

Total 386 - 603 - 0.13159 14.214 311.8 1,725.21Gf= 17..25


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N = 7.918x10 6

Using the figures in Table 7.3.6, the Intensity Growth factor (I Gf) was computed from therelation below proposed by Mukabi, 2002c:-

n

iiiGf xESALG I

11001 (7.4)

The resulting Intensity Growth Factor was I Gf = 17.25

7.5 Analysis of Relative Damaging EffectIf the existing pavement has been subjected to repetitions of axle loads of various magnitudesand as a consequence undergoes considerable amount of structural damage. The damagingeffect (RD eff.), the single passage of a load (Ls) or an axle group is computed from theapproximation equation introduced by Mukabi (2002c):-

GF

C

W

W eff I x EL

L RD )01.0(. (7.5)

where,RD eff. = Damaging effectLW = Load on the axle groupELW = 8.2 tonnes in the case of a single axle with dual tyres.C = an exponent considered as C= 4 in this caseIGf = Intensity of Growth factor related to increase in cumulative ESAL

Impact of Dynamic Loading on Structural Layer ThicknessDeterioration in pavement layer thickness usually results in the loss of structural capacity ofthe road pavement. It is therefore imperative to investigate this component in order to

determine the appropriate engineering design and construction for proper maintenance. Inthis section, the deterioration of layer thickness is treated as a structural component as theactual deficiency in structural capacity in quantitative terms due to loss in pavement thicknessis also evaluated.

After computing the loss of pavement layer thickness by comparison of the pre-loadingand post-loading thicknesses for each layer and adopting the structural capacity depreciationfactor (f sd ) and the corrected Resilient Modulus (M rcor. ), values determined from the equationfor the required thicknesses are computed.

The conversion factors (C f) of each existing pavement layer are computed asdepreciated values from the product of the proposed conversion factors C f P and f sd (Mukabi,2002c). Hence,

C f = C fP x fsd (7.6)

The effective thickness is whence calculated as :-Te = T eE x C fP x fsd (7.7)

where,TeE = Existing thickness.

The subgrade CBR dBD determined during the Basic Design Study is also depreciated by thesame factor and the CBR dDD adopted is therefore calculated as :-

CBR dDD = CBR dBD x fsd (7.8)

The overlay thickness (T o) required was then determined from :To = Tn - Te (7.9)


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7.6 Selection of Appropriate Traffic ClassThis was based on the Traffic Classes specified by TRL Overseas Road Note 31 andthe traffic class was T7.

8. ENGINEERING ASSESSMENT, EVALUATION AND ANALYSIS8.1 Intrinsic and OPMC Stabilized Material Properties The intrinsic and OPMC stabilized material properties were presented, comprehensivelyanalyzed and discussed in Chapter 5 of Engineering Report no. SST1 of May 2007.A summary of the main engineering parameters is presented in sub-section 7.2.2.

8.2 Analysis of The Impact of Environmental Factors Under sub-section 4.1.9 of Engineering Report no. SST1 of May 2007, the conceptsapplied for analyzing the impact of environmental factors were introduced.

Consequently, applying the data that was determined in this study, engineering analysisof each environmental factor that is likely to affect the performance of the pavementstructure is made. The effect of OPMC stabilization components on some of theenvironmentally related factors on the subgrade soils tested in this study is alsodemonstrated in Figures 8.1 and 8.2, while some. In general terms, plasticity index is afunction of the amount of clay present in a soil, while the Liquid Limit and Plastic Limitsindividually are functions of both the amount and type of clay. High plasticity indices areanalogous to high water contents whose lubricating effect of the water films betweenadjacent soil particles tends to reduce the mechanical stability, strength and deformationresistance. This phenomenon is quantitatively illustrated by the generalized empiricalequations proposed by Mukabi et al. (2001c) for tropical soils with a PI < 43.

On the other hand, Mukabi (2001e, 2003a) proposed an empirical formula relating thebearing capacity based on CBR for materials where CBR 50, and UnconfinedCompression Strength (UCS) defined as:

where,

gl = 14.4 and gi = 46.6being the gradient linear andgradient intercept of mostgeomaterials tested in the2001 Study and,

Figure 8.1 Effect of cement stabilization on the PI of sandy clayand Figure 8.2 Effect of lime stabilization on the PI of sandy clay

OPMC giugl f qCBR }{ (%) (7.10)

Rewriting Equation 7.14 we obtain,

OPMC

gi

gl

uf

CBRq 1

(kgf/cm 2) (7.11)


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opt I I cr sopt OPMC BR BR R f f is a strength and moduli ratio parameter derived from theinfluence of OPMC Stabilization.

Substituting for uq in Equations proposed by Mukabi et al. (2001c) we obtain,

qq

OPMC

imcgi

gl

OPMC

umcgi

gl

mc PI

f CBR

f CBR

1

1

(%) (7.13)

Mukabi (2001e) also proposed the following empirical formula that correlates the bearingcapacity expressed in terms of CBR and the Plasticity Index, which is expressed inEquation 7.14.

35m BC

glgi CBRPI

(%) (7.14)

Where,gi = 0.97, gl = 0.027 and BC = 0.564 being the gradient linear, gradient intercept

and Bearing Capacity materials constant of most geomaterials tested and,CBR m is the measured CBR value obtained at a density corresponding to 95% MDD inaccordance to AASHTO T-180 Method D for various soaking and curing periods.

A more universal empirical equation that considers all factors including the effects ofOPMC stabilization, variation in material properties, modes of mechanical and chemicalstabilization, the quantum of various etc. is presented in Equation 7.15 below.

giglu CBRq ln (kgf/cm2) (7.15)

Substituting for uq from Equation 7.15, we obtain Equation 7.16 as follows,

qq

imcgigl

umcgigl

mc PI CBR

CBR

ln

ln(%) (7.16)

Where,gl = 12.9, and gi = 36.5 being the gradient logarithmic, and gradient intercept materials

constants for most geomaterials tested.Simulating Effect of Moisture~Suction Variation on The Unconfined Compression Strength(UCS) for Natural Gravels ( Without OPMC Stabilization)


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Simulating the Effects of Moisture-Suction Variation for Natural/Gravel withoutOPMC Stabilization

Table8.1 When PI=12, M ci=5.1% q u at Initial q u = 13.8kgf/cm 2 for Subbase Material

Fig. 8.3 Variation of moisture content vs. variation in UCS when PI=12

Table 8.2 When PI=6, M ci=5.1% at Initial q u = 39.2kgf/cm 2 for Base course material

Fig. 8.4 Variation of moisture content vs. variation in UCS when PI=6

From the foregoing data, the significant impact of moisture~suction variation andplasticity on the vital engineering parameters of geomaterials can be appreciated.It is therefore vital that the use of combined cement and lime treatment be applied for therelatively sandy clays found in the project area as can be derived from the graphspresented in Figures 8.1 and 8.2.

Simulating Effect of Moisture~Suction Variation on The Unconfined Compression Strength(UCS) With OPMC Stabilization

In this case the quantitative effects of moisture~suction variation for materials subjectedto OPMC stabilization are presented based on the data that was determined in thisStudy.The results are tabulated in Tables 8.3 ~ 8.4 and Figs. 8.5 ~ 8.6


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Simulating The Effects of Moisture-Suction Variation for Natural Gravel withOPMC Stabilization

Table 8.3 When PI=12, M ci=5.1% at Initial q u = 13.8kgf/cm 2 for Subbase Material

Fig. 8.5 Variation of moisture content vs. variation in UCS

Table 8.4 When PI=6, M ci=5.1% at Initial q u = 39.2kgf/cm 2 for Base course Material

Fig. 8.6 Variation of moisture content vs. variation in UCS

Effect of SwellingAs can be noted from previous discussions on swell characteristics, for even the worst ofgeomaterials, the maximum swell actually reaches a residual state after a maximum of10hrs and not 96hrs as conventionally considered.Mukabi et al (2001a). also showed that for most geomaterials, swell can be contained byapplying a surcharge pressure of approximately 24KPa as can be derived from Equation17.20.

scscscsc ln (%) (7.7)Where,

sc Swell in relation to surcharge pressure

sc 12.9; logarithmic gradient constant for standard tropical geomaterials

sc Surcharge Pressure in KPa

sc 36.5; logarithmic intercept constant for standard tropical geomaterialsTable 8.5 is a summary of swell at varying surcharge pressures, while the characteristic curveis plotted in Fig. 8.7.


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Effect of Variation InDesign MoistureContentThe selection of anappropriate designmoisture content anddensity condition iscritical to the designanalysis and

subsequentconstruction QualityControl. The moisturecontent at whichsubgrade, subbase andbase course strengthshould be assessed isthat which can be

expected to beexceeded onlyrarely.Pronouncedexceedance ofthis factor isknown to haveadverse effectson the pavementstructure.

Equation 7.8,which definesthe relationshipbetween theratio of DesignMoisture Contentof the dry andwet seasons andthe Plasticity Index, is applied in formulating the data in Table 8.34 and the graphicalrepresentation in Fig. 8.8.

glgl DMC PI ln (7.8)Where,

DMC Design Moisture Content Ratio

gl 0.12; logarithmic DMC gradient constant for tropical geomaterialsPI Plasticity Index of the geomaterial to be utilized for construction

gi 0.7; logarithmic DMC intercept constant for tropical geomaterials

Correction factors for the Plasticity Indices and the Design Moisture Contentsrespectively during the wet and dry seasons are defined in the following relations.

w

Bp

pd PI e API (7.9)Where,

p A = 12; linear gradient constant for PI for tropical geomaterials

Table 8.6 Plasticity and Seasonal Effects on the Design Moisture Content

Fig. 8.8 Plasticity and Seasonal Effects on the Design Moisture Content

Table 8.5 Effect of Surcharge Pressure on Swell Factors

Fig. 8.7 Effect of Surcharge Pressure on Swell Factors


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d PI Plasticity Index of the geomaterial during the dry season Bpe Annual Evapotranspiration Factor

BP = 0.02; Exponential constant for PI for tropical geomaterialswPI Plasticity Index of the geomaterial during the wet season

mcd Bm

mmcw De A D (7.10)

Where,m A = 0.97; linear gradient constant for DMC for tropical geomaterials

mcw D Design Moisture Content of the geomaterial during the dry season

BM e Annual Evapotranspiration FactorBm = 0.03; Exponential constant for DMC tropical geomaterials

mcd D Design Moisture Content of the geomaterial during the wet season

From the above equations, Mukabi et al. (2007f) developed the relations in Equations7.11 ~ 7.13, which correlate the ratio of the seasonal bearing strength, CBR and theresilient modulus, M r , presented in Table 8.35, the graphs of which are shown in Figs.8.9 ~ 8.12.

Seasonal Effects On Bearing Capacity and Resilient ModulusThe combined effects of seasonal changes and soaking conditions on the bearing capacityand resilient modulus of some subgrade, subbase, and base course materials is presented inTable 8.7 and depicted in Figs. 8.9 ~ 8.12, while the equations that can be applied to correctfor this effect are presented as follows.The relation between the CBR wet and dry season ratio vs. the CBR determined during thewet season is correlated as follows.

giwglwdr CBR ln (7.11)

Where,wd r = Wet

to Dry Season BearingStrength Ratio

gl =0.0022; logarithmic CBRgradient constant fortropical geomaterials

gi =0.54; logarithmic CBRintercept constant fortropical geomaterialsThe relation between theCBR wet and dry seasonratio vs. the CBRdetermined during the dryseason is correlated asfollows.

gid glddr CBR ln (7.12)Where,

wd r = Wet to Dry Season Bearing Strength Ratio

Table 8.7 Comparison of wet and dry seasons,CBR's and Resilient Modulus


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gl = 0.0022; logarithmic CBR gradient constant for tropical geomaterials

gi = 0.54; logarithmic CBR intercept constant for tropical geomaterials

gir glwMr M ln (7.13)

Where,wMr = Wet to Dry Season Resilient Modulus (M r ) Ratio

gl = 0.0022; logarithmic M r gradient constant for tropical geomaterials

gi = 0.54; logarithmic M r intercept constant for tropical geomaterials

Fig. 8.9 Effect of CBr w/CBR dr on Wet CBR Fig. 8.10 Effect of CBr w/CBR dr on Dry CBR

Fig. 8.11 RM wet /RMdry vs. Wet RM Fig. 8.12 RM wet /RMdry vs. Dry RM

Intrusion Of Native Subgrade Material Into Upper Layers of Pavement Structure


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Various research undertaken by Mukabi (2001) and Mukabi et al. (2003) indicate thatIntrusion of native subgrade material into the overlying layers of the pavement usually resultsin the ultimate degradation of the layers whilst causing gross variability in the quality ofpavement layer materials and thickness.Depending on the nature of the subgrade, topography of environment and seasonalchanges, intrusion of native subgrade material into overlying layers of the pavement structure,as depicted in Figs. 8.14 of this paper, can be rampant and extremely detrimental.

The quantitative assessment of deficiency in the physical properties of pavementmaterials with time due to the intrusion of fines into the upper pavement layers is undertakenby employing Equation 7.14 proposed by Mukabi et al. (2003b) and Equation 7.15 proposedby Mukabi et al. (2007f).

SCBR USmm CBRPI (7.14)

Where,

SCBR = Soaked CBR

m = 0.97; linear CBR s gradient constant for tropical geomaterials

m = 0.027; linear CBR s intercept constant for tropical geomaterials

USCBR = Unsoaked CBR

DC B A

CBRCBR init ult 23

.. (7.15)

Where,

.ult CBR Ultimate CBR

.init CBR Initial CBR

A = 0.00057, B = 0.028, C = 0.15, and D = 1.39 are material constants

= Black Cotton Soil Intrusion Content.

Fig. 8.13 Effects of Inferior MaterialIntrusion in upper layers

Fig. 8.14 Influence of Black cotton SoilIntrusion on Bearing Strength


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The results computed by adopting Equation 7.15 are summarized in Table 8.8 and thecharacteristics are shown in Figs. 8.15 and 8.16 for the bearing capacity and resilient modulusrespectively.

Table 8.8 Effects of Inferior Material Intrusion in upper layers for CBR=245

Fig. 8.15 Effects of inferior material Intrusion in upper layers

Evaluation of Variation in Quality of Pavement Layer Materials Based onStatistical Concepts

Due to the effects of cyclic and dynamic loading as well as various environmental factors,the quality of pavement layer materials tends to deteriorate with time.

To demonstrate this fact, deterioration in pavement layer thickness parameters relatedto deviation and variance are tabulated in Table 8.9. In this table, the parametersdetermined in various parts of the Eastern Africa Region are compared to values adoptedas standard in indicating pavement layer variability in America recommended by the

Bureau of Public Roads. In making this comparison, it is assumed that that the variancein strength is directly proportional to the variance in layer thickness, based on theanalysis of strength and layer thickness parameters reported by Mukabi et al. (2003c).


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Table 8.9 Pavement Layer Variability-Layer StrengthLayer Type of

StrengthTest

Variance S PercentageDifference

(%)

Coefficient ofVariation (C.V)

PercentageDifference

ThisStudy

BPR,USA

ThisStudy

BPR,USA

Surface CBR 5.18 - - 74 - -

Base Course CBR 12.85 35.5 3.2

Subbase CBR 23.8 7.6 >213 107.2 36.9 >191

Subgrade CBR - 0.9 - - 21.4 -

Notes : BPR, USA : Bureau of Public Roads of the United States of America, < : Indicates values of this Study as lessthan those recommended by BRP, > : Indicates values of this Study as greater than those recommended by BRP.

The above comparison shows that, whereas the variability of the base course layer wasalmost similar to that recommended by the Bureau of Public Roads of the USA, thesubbase variation values determined in this particular Study are extremely high. Thisimplies that the variation in thickness as a result of structural deterioration of thepavement was in a critical state. It can also be derived from these results that due to thevarious factors evaluated in the preceding sections, most of the subbase layers of theexisting pavement have been contaminated and subsequently structurally damaged.It is therefore imperative that the pavement structure is designed taking this factor intoserious consideration.

Deterioration of Pavement Structural Thickness

Deterioration in pavement layer thickness usually results in the loss of structural capacityof the road pavement. It is therefore imperative to investigate this component. In thissection, the deterioration of layer thickness is treated as a structural component, whilstthe actual deficiency in structural capacity in quantitative terms due to loss in pavementthickness, is evaluated in section 4.1.Table 8.1.1 in Chapter 8 presents the postulated results of the evaluation of thedeterioration in pavement layer thickness of the composite pavement structure with time.This is mostly attributed to the environmental influence on the structural resistance of thepavement.

8.3 Recommended Specifications for Materials Strength and DeformationProperties

8.3.1 Strength and Deformation PropertiesAs has been discussed in various sections of this Report, optimum mechanical stabilitycontributes immensely to the strength and deformation resistance of geomaterials.It is therefore extremely important that this factor be taken into serious considerationwhen carrying out Quality Control during construction.The mechanical stability requirements for materials to be used for subbase and basecourse are stipulated in the following Tables, which are excerpts from Transport andResearch Laboratory (TRL) Overseas Road Note 31-A guide to the structural

design of bitumen-surfaced roads in tropical and sub-tropical countries.


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8.3.2 Linear Elastic and Recoverable RangeThe importance ofdetermining the range oflinear elasticity andrecoverability has beenextensively discussed in thisReport and cannot thereforebe overemphasized.For the materials tested forthe purposes of Design andQuality Control for thisProject, this range has beenquantitatively computed byapplying the equation firstproposed by Mukabi (1995b)and later modified by Mukabi

et al. (1999c).The data obtained from this Study for facilitate the design is summarized in Table 8.10(a)and (b) and Fig. 8.17(a) and (b).

8.4 Analysis of Problematic and/or Expansive Soils8.4.1 PreambleBlack cotton soils areusually tropical clayswhich are essentiallyproducts of physical andchemical in-situweathering of igneous,sedimentary andmetamorphic rocks undervarying environmentalconditions. The formationof these soils is highlyinfluenced by a complexinteraction of variousvariables, such asweathering, erosion andclimatic changes as well as type of original parent rock, local topography, drainage andcycle factors which strongly influence their engineering behaviour. As a consequence,their characterization for use as suitable engineering materials becomes extremelycomplex since they are highly susceptible to various environmental changes.These soils are also known to be highly susceptible to pore-grain moisture-suctionmatrices characterized mainly by swelling due to wetting and shrinkage due to drying thatprompts accelerated reduction or gain in strength respectively. Changes in the plasticitycharacteristics of these soils are known to be influenced by the wetting and dryinghistorical hysteresis (Ref. Pandean et al. 1993, Mukabi, 1998).

Table 8.10(a) Effects of Moisture-suction variation on the Elastic Limit Strain( a)ELS for Natural Gravel with OPMC stabilization: When PI=6, Mci=5.1% at

Initial [( a)ELS ]imc =0.574 x 10 -3

Fig. 8.17(a) Effects of Moisture-suction variation on the Elastic Limit Strain

(a)ELS

Table 8.10(b) Effects of Moisture-suction variation on the Elastic Limit Strain( a)ELS for Natural Gravel with OPMC stabilization: When PI=0, Mci=5.1% at

Initial [( a)ELS ]imc =0.574 x 10 -3

Fig. 8.17(b) Effects of Moisture-suction variation on the Elastic Limit Strain( a)ELS


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8.4.2 Some Recently Developed Applicable Pragmatic Engineering Solutions1.Rerap Methods

Table 8.11 - Determining Required Capping Layer Thickness (cm) for RE 1 TypePhase II

Tables 8.11and 8.12 as well as Figures 8.18 and 8.19 show the design and QC criteriadeveloped on the basis of research and adopted for the construction of the Addis Ababa~ Goha Tsion Trunk Road Project. In determining the necessary thickness CLt to replacethe expansive soil, the following equations proposed in this study were adopted.

SPb pPCL xSt T t (7.14)

The total pavement thickness T P is expressed as:

v f bPP t xRt T (7.15)

And the coefficient of subgrade structural performance S SP is computed from:

5.0 / / 1 ed CBRSP eS (7.16)On the other hand, the basic pavement thickness t P b from Eq. (7.16) is computed fromthe following equation.

Pd Pd PP

bP

D N

CBRC CBR B At

/ log

loglog 2

(7.17)Where the roughness factor 25.02 it i f R R R R : R i is the initial roughness factor and R t isthe terminal roughness factor, t V in Equation 7.29 is the positive value of the specifiedtolerance for pavement thickness, A P=219, B P=211, C P=58 and D P=120. The parameter

e in Equation 7.30 is defined as: cneee M LLV C B

ee e A (7.18)where A e=0.23, B e=0.54, C e=0.08 are constants and V e=Annual AverageEvapotranspiration in m/year (ref. to Mukabi et al. (2003c), LL=liquid Limit in percentageand M cn =Natural Moisture Content of the subgrade material expressed in percentage

form. All thickness are calculated in mm. Continuous assessment and evaluation of theperformance of the sections already constructed by adopting this criteria indicates thatthe method has so far been quite successful.

C o

d i n g

O p

t i o n

Plasticity andSwell Condition

Required Thickness forDifferent SubgradeBearing Capacity

P l a s t

i c i t y

I n d e x

S w e

l l ( % ) S m

C B R =

1

C B R =

2

C B R =

3

C B R =

4

4 < C B R < 7

A PI>45 Sm>10 140 90 70 60 30B 35


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Figure 8.18 - Layer thickness (1


22/37


Table 9.2 Coarse aggregate for bituminous mixes

Notes. 1. British Standard 812, Part 103 (1985 5.ASTM C131 and C535 2. J C Bullas and G West (19910 6. British Standard 812, Part 121 (1989)3. British Standard 812,Part 105 (1990) 7. British Standard 812, Part 2 (1975)4. British Standard 812, Part 3 (1985) 8.Shell Bitumen Handbook, D Whiteoak (1990)

Comparing the test results obtained from this Study and the Design Criteria stipulated inTable 9.2, the following facts can be derived.

1. The Flakiness Index (FI) is way below the maximum allowable (acceptable) value byapproximately 300%.

2. The Los Angeles Abrasion Value (LAA) is above the acceptable Criteria byapproximately 67%.

3. The Durability test results defining the Sodium Sulphate Soundness overshoots theacceptable Design Criteria by approximately 105%.4. The Water Absorption and Bitumen Affinity tests indicate that the both results are much

more superior in comparison to the Design Criteria with the Water Absorption less bymore than 6.67 times and the Bitumen Affinity greater than 95% without anysegregation upon soaking.

In conclusion, the lateritic quartzic materials can be used for surface dressing by employing aspecial method of construction that will ensure the particles pack properly in order to achievean Optimum Mechanical Stabilization and a homogeneous slurry spray of the bitumen.

It is recommended that the OBRM (Optimum Batching Ratio Method) proposed by Mukabi(2001a) and Mukabi and Shimizu (2001b) be employed in order to achieve this criteria.

Property Test SpecificationCleanliness Sedimentation of Decantation ( 12) < 5 per cent passing

0.075 mm sieve

Particle shape Flakiness Index ( 3)


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10. STRENGTH OFEXISTINGSUBGRADE

In most cases,subgrade strengthand characteristicsdetermine theperformance offlexible pavementstructures.Due to thecomplexity of

maintaining the existing moistureregime of subgrade soils forlaboratory testing, it is usuallyrecommended that directmeasurements of CBR underexisting pavements, in-situmeasurements have been found toproduce fairly reliable resultsprovided that the appropriateanalytical tools are applied.For design purposes it is importantthat the strength of the subgrade isnot seriously underestimated for

large areas of pavement oroverestimated to such an extent thatthere is a risk of local failures.The behaviour of subgrade groundunder plate loading tests wasdiscussed under section 5.7 ofChapter 5 of the Engineering ReportNo. SST1, May 2007.It can be noted that the recoverable

behaviour is more pronounced in the initial load-unload-reload cycle.

The results of the maximum settlement against the corresponding pressure from thePlate Loading Tests are summarized in Table 10.1. In-situ test results from Dynamic Cone Penetration Tests were also reported undersection 5.4 of Chapter 5 of the Engineering Report no. SST1 of May 2007.The average (mean) CBR m values determined from these results over a depth of 1 metre,are presented in Table 10.2. The mean values were computed by applying Equation 10.1

3

31

31

2231

11

100

............. nnm

CBRhCBRhCBRhCBR (10.1)

Table: 10.1 Existing Sub-grade Characteristics Based on Plate Loading TestsTestNo.

TestingDepth(m)

Pressureon Plate

AverageMaximumSettlement(mm)

Basic Testing Conditions

1. 0.25 2.72 3.37 Test Under Relatively Moist Conditions2. 0.25 2.51 0.92 Tested Under Relatively Dry Conditions

3. 0.53 2.11 0.45 Tested Under Relatively Dry Conditions4. 0.25 2.17 20.9 Soaked for 24 hrs and Tested under Soaked

Conditions5. 0.25 2.91 3.48 Tested Under Relatively Moist Conditions6. 0.58 3.36 2.38 Tested Under Relatively Moist Conditions7. 0.25 2.26 4.43 Tested Under Relatively Moist Conditions8. 0.25 3.25 1.93 Tested Under Mildly Moist Conditions9. 0.25 1.63 1.41 Tested Under Monotonic Cyclic Loading Conditions

10. 0.25 0.82 26.0 Soaked by Rain for 16 hrs and Time ControlledLoading

Table 10.2 Subgrade Strength CBR Design Values Subgrade Strength-CBR Design Values

TestNo.

TestCondition

TestLocation

CBRMean

1 Dry RHS 16 10.042 Dry RHS

35.26.93

3 Dry LHS 70.2 21.544 Dry RHS

70.27.96

5 Saturatedsoil

Nearriverbank

3.31

6 SwampyArea

Nearriver

bank

1.62

7 Dry Area Nearriverbank

3.92

8 Soaked RHS 16 17.939 Soaked RHS

35.212.32

10 Soaked RHS70.2

18.69


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Table 10.3 Subgrade Strength CBR by Sub Section of Juba River Port access road

Fig. 10.1 Subgrade CBR Mean by Sub-section and Location

On the other hand, the Subgrade Strength Classes based on CBR values as specified by TRLOverseas Road Note 31 are presented in Table 10.4. Utilizing the values in this table and the materialproperties of subbase and base coursedetermined in this Study, the pavement structureis then designed as illustrated in section 11.The section CBRs will be determined afterfurther detailed in-situ testing of the subgrade by

use of DCP.

11. PAVEMENT STRUCTURAL DESIGN11.1 Basic Method AppliedHaving determined the design CBR values for the subgrade as well as the subbase and basecourse, the pavement thickness of each layer is designed so that the desirable T A value isassured and the total thickness H of the surface course, base course and the subbase courseis designed to be greater than 80% of the target value.In this case a pavement structure that considers a double seal surfacing course, an OPMC L4 stabilized base course and OPMC L6 stabilized subbase course and against the existing

subgrade strength and intrinsic characteristics, which were previously discussed and theanalysis done in Chapter 5 of the Engineering Report No. SST1 of May 2007.The calculated T A values are then compared with the standard target values listed in Table11.1 subsequent to which another calculation is conducted to obtain the final pavementstructure configuration if the value of T A falls below the target, or the total pavement thicknessH is found to fall below more than 20%. The T A value is calculated by the following equation:

nn A T aT aT aT .........................2211 (11.1)

Where,

naaa ...,.........., 21 = Conversion coefficients shown in Table 11.2nT T T ..,.........., 21 Thickness of each layer in cm.

able 10.4 Subgrade strength classes (CBR%)S1= 2S2= 3,4S3= 5 7S4= 8 14S5= 15 29S6= 30+


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Table 11.1 Target Value for T A and Total Thickness(Source: Japan Road

Association 1989)Note 1: T A represents the

pavement thicknessrequired if the entire

depth of thepavement were tobe constructed ofhot asphaltmixtures, used forthe binder andsurface course (seesections 2-1-3-6 and 2-1-3-7 of the JRA).

Note 2: In the case of a road with various CBR values in the vertical direction, a filter course need not be constructed,provided the CBR value of the uppermost layer is 3 or more, and its thickness is 30cm or more, even if the designCBR value is 2.

Note 3: Traffic Class T7 of The TRL Overseas Road Note 31 is equivalent to C Traffic of The Japan Road Association, 1989and Class T2 of the Kenya Road Design Manual.

Notes: Conversioncoefficients listed in Table7.6.2 indicate the ratio of the thickness of the

pavement by each method and material of constructionto the thickness of hot asphalt mix for the binder and the surface coursescorresponding to thethickness of each material.

Thus, the term nnT a of Equation 7.37 indicates thecorresponding thickness of the n-th layer converted thickness of hot asphalt mix

for the binder and surfacecourses. For example; 1 cmof pavement adoptingmechanical stabilizationcorresponds to 0.35 of

pavement adopting the hot asphalt mix method , and 20cm of pavement using thehot asphalt mix method (0.3520=7)..

Also note the OPMC conversion Values determined empirically for varying OPMC Stabilization levels.

Table 11.3 Standard Thickness of One Finished Layer After Compaction (cm)Stabilization

MethodClassification of Pavement

General traffic Light trafficBase Subbase Base Subbase

Cement

stabilization

10~20 15~30 12~20 12 or more

Lime stabilization 10~20 15~30 10~20 10 or more

Table 11.2 Conversion Co-efficient for the Calculation of T A PavementCourse

Method andMaterial of Construction

Conditions StandardCoefficient, a n

OPMCCoefficient,an(OPMC)

Surface &Bindercourse

Hot asphalt mix forsurface and bindercourse

1.00

Base BituminousStabilization

Hot-mixed stability:350kgf or moreCold mixed stability250 kgf or more

0.80

0.55

CementStabilization

Unconfined compressionstrength (7days):30 kgf/cm 2

0.55 OPMC Level4 = 0.65

Lime stabilization Unconfined compressionstrength (10 days):10kgf/cm 2

0.45 OPMC Level6 = 0.78:Cement/LimeCombination

Crushed stone formechanicalstabilization

Modified CBR value: 80 ormore

0.35

Slag for mechanicalstabilization

Modified CBR value:80 or more

0.55

Hydraulic slag Unconfined compressionstrength (14 days) 12kgf/cm 2 or more

0.55

Sub-base Crusher-Run, slag,sand, etc

Modified CBR value:30 or more20 to 30

0.250.20

Cement stabilization Unconfined compressionstrength(7 days):10kgf/cm 2

0.25

(Source: Japan Road Association 1989 and Mukabi, 2004a for the OPMC Stabilization Conversion Coefficients)

DesignCBR

Target Value (cm) L Traffic A Traffic B Traffic C Traffic D TrafficTA Total

Thickness HTA Total

Thickness H TA Total



Thickness H 2 17 52 21 61 29 74 39 90 51 1053 15 41 19 48 26 58 35 70 45 904 14 35 18 41 24 49 32 59 41 706 12 27 16 32 21 38 28 47 37 558 11 23 14 27 19 32 26 39 34 4612 - - 13 21 17 26 23 31 30 3620 - - - - - - 20 23 26 27


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Note: Although the gradings listed inTable 4.4 are not absoluterequirements, it is desirable that materials include some coarse particlesand maintain continuous grading for ease of mixing and compaction. Very

poorly graded materials, or a cohesivesoil of high plasticity, tend to require alarge amount of additives to achieve thedesired effect of stabilization, and are,consequently, economically unfavourable.

Design Computation For Type I :

Case I-1: Base Course Directly Placed on Existing SubgradeFrom Table 7.6.1, based on the results from Table 7.5.3 when the mean Design CBR =8, the required T R A = 26cm and the Total Thickness H = 39cm.Considering that a SC = 1.0, T SC = 10cm, a BC = 0.78 and T BC = 20cm then the DesignT D A is computed as :

T D A = 1.010+0.7820= 25.6cm

From the above computation and design criteria,25.6 cm < 26cm, Hence, DESIGN VALUE IS NOT ACCEPTABLE

Case I- 2: Slightly Thicker Base Course Directly Placed onExisting Subgrade

Considering that a SC = 1.0, T SC = 10cm, a BC = 0.78 and T BC = 25cm then the DesignT D A is computed as :

T D A = 1.010+0.7825= 29.5 cm

From the above computation and design criteria,29.5 cm > 26cm, Hence, DESIGN VALUE IS ACCEPTABLE

In this case, the typical cross-section of the pavement structure would be as depictedbelow.

CarriagewayShoulder

Gravel Wearing Coursefor Shoulders

Carriageway Shoulder

Existing Sub grade1.8


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Fig. 11.1 typical Cross section Type I-2 depicting pavement structure

Fig. 11.1 Typical Cross section Type I-3 depicting pavement structure

Case I- 3: Base Course Directly Placed on Existing Subgrade withCBR > 20

From Table 11.1, based on the Table 7.5 .., when the mean Design CBR > 20, therequired T R A = 20cm and the Total Thickness H = 23cm.

Considering that a SC = 1.0, T SC = 10cm, a BC = 0.78 and T BC = 20cm then the DesignT D A is computed as :

T D A = 1.010+0.7820= 25.6 cm

From the above computation and design criteria,

25.6 cm > 23cm: Hence, DESIGN VALUE IS ACCEPTABLE


CarriagewayShoulder


Carriageway Shoulder

Existing Sub grade

CBR>20t

A

=200mmBC OPMC Level 5 StabilizedGravel Base Course50:25:25:8:4 {Natural Gravel: Aggregate:Sand}:Cement: Lime

SideDitch

Design Computation For Type II :

Case II-1: Base Course Directly Placed on Existing Subgrade in SwampyAreasFrom Table 11.1, based on the results from Table 7.5 .., when the mean Design CBR= 2 in swampy areas, the required T RA = 39cm and the Total Thickness H = 90cm.Considering that a SC = 1.0, T SC = 10cm for Surface Course, a BC = 0.78, T BC = 25cm,Base Course then the Design T DA is computed as :

TDA = 1.010+0.7825= 29.5 cm

From the above computation and design criteria,25.6 cm < 39cm, Hence, DESIGN VALUE IS NOT ACCEPTABLE

Table 10.3


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Fig. 11.2 Cross section Type II-2 -typical pavement structure for swampy areas or expansive soils

In case of extreme environmental and geological problems, Type II -3 shall be applied. Crosssection Type II-3 is illustrated in Fig. 1.3.

Fig. 11.3 Typical Cross section Type II-3 depicting typical pavement structure for swampy areas orexpansive soils in extreme conditions

Case II-2: Base Course Placed on Improved Subgrade in SwampyAreas

Applying the ReRap Method introduced in Table From Table 11.1, based on the resultsfrom Table 7.5 .., when the mean Design CBR is improved from CBR = 2 to CBR = 30with a Capping Layer thickness of 40 ~ 50cm in the swampy areas, then the requiredT R A = 20cm and the Total Thickness H = 23cm with a Capping Layer Thickness of C p =50cm.

Considering that a SC = 1.0, T SC = 10cm for Surface Course, a BC = 0.78, T BC = 20cm,Base Course then the Design T D A is computed as :

T D A = 1.010+0.7820= 25.6cm

From the above computation and design criteria,

25.6 cm > 23cm: Hence, DESIGN VALUE IS ACCEPTABLE


Existing Sub grade

CarriagewayShoulder Carriageway Shoulder SideDitch


t A

=50mm ASOPMC Level 5 Stabilized Gravel Base CourseSand Filter

Natural Sand and/or Gravel Pebbles, Filter Layer

t A

=200mmBC

t A

=200mmBf Natural Gravel Capping Layert

A

=500mm Af

DBST Wearing Course

Existing Sub grade

CarriagewayShoulder Carriageway Shoulder Side

DitchGravel Wearing Coursefor Shoulders

t A

=50mm ASOPMC Level 5 Stabilized Gravel Base CourseSand Filter

Natural Sand and/or Gravel Pebbles, Filter Layer

t A

=200mmBC

t A

=200mmBf Natural Gravel Capping Layert

A

=500mm Af


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The results of other design computations with varying conditions that were assessed andevaluated on site are given in Table 11.5.

Table 11.5 T RA and Total Thickness, H Design Parameters for Varying Conditions

12. ANALYSIS OF STRUCTURAL SOUNDNESS OF COMPOSITE PAVEMENTSTRUCTURE

12.1 Analysis of Deterioration of Structural Capacity and Serviceability Levels withProgression of Time

12.1.1 Definition of Functional and Structural FailuresDistinctively, there are two different types of failure. The Structural Failure includes a collapseof the pavement structure or a breakdown of one or more of the pavement components ofsuch magnitude to make the pavement incapable of sustaining the loads imposed upon itssurface. The second type is classified as functional failure and may or may not beaccompanied by structural failure but is such that the pavement will not carry out its intendedfunction without causing discomfort to passengers or without causing high stresses in the

vehicle that passes over it due to roughness. Obviously the degree of distress for bothcategories is gradational, and the severity of distress of any pavement is largely a matter ofopinion of the person observing the distress. As an example, consider a rigid highway

ItemNo. PavementType Sub-section Conditions

Sub-

sectionLength (m)

Pavement Structure Design Parameters

Combined Sub-grade CBR %

TR A (cm)

TotalThickness H(cm)

Structural Layer Configuration

1 I-2

Existing Sub-gradecomposed of NaturalGravel with appreciableStructural Capacity of Layer Thickness tNG>20cm

CBR 2026

(29.5)39

(39.50

2. I-3

Existing Sub-gradecomposed of NaturalGravel with HighStructural Capacity of Layer Thickness tNG>20cm

2020

(26.5)23

(30)

3. II-2Swampy Areas with weaksub-grade computed of Expansive Soil

239/23

*(26.5)*

90/31*(90/30)*

4. II-3Swampy Areas with weaksub-grade computed of Expansive Soil

239/23

*(26.5)*

90/31*(90/30)*

5. III-2Areas with Type I-2Subgrade but poorDrainage

8 CBR 20


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pavement that has been resurfaced with an asphaltic overlay. The surface may develop roughspots as a result of breakup in the bituminous overlay (functional failure) without structuralbreakdown of the overall structure. On the other hand, the same pavement may crack andbreak up as a result of overload (structural failure). Maintenance measures for the firstsituation may consist of resurfacing to restore smooth riding qualities to the pavement.However, the structural type of failure may require complete rebuilding.

12.1.2 Analysis of Structural CapacityTable 12.1.1 is a summary of design parameters determined at equilibrium moisture content.On the other hand, a summary of the deterioration factors and depletion with the progressionof the pavement structure due to seasonal cycle and dynamic loading effects is given in Table12.1.2 and 12.1.3, while the characteristic curves are presented in Figs. 12.1.1 ~ 12.1.3.

The data wasgenerated byapplying thefollowing empiricalequationsdeveloped andproposed byMukabi (2004) andMukabi et. al.(2007f).

SC t SC t SC SC t C N B N A f (12.1)

Where,SC t f Time dependent Structural Capacity Factor

SC A 0.001, SC B 0.0507 and SC C 1.13 are Structural Capacity~Time relatedconstantst N Time Progression in Years

The Structural Capacity Deteriorating Factor, SC d f is then computed as:

thrumsvSC t

SC d f f f f f .int (12.2)

Where,msv f Moisture~Suction Depreciating Factor

.int ru f = Inferior Material Intrusion Depreciating Factor

th f Pavement Layer Thickness Depreciating FactorEquations 7.24 ~ 7.28 are then applied.

a. Without Any Maintenance Scenario The case whereby NO maintenance is undertaken is presented in Table 12.3.1 and Figs.

12.3.1 ~ 12.3.3.It can be noted that in this case the pavement structure deteriorates to reach a critical statethat requires resurfacing after 8 years.

Table 12.1.1 Summary of design parameters at equilibrium moisture contentMode of

stabilizationLayertype

Design parameters

qu(kgf/cm 2

)

Emax(kgf/cm 2

)

( a)ELS x 10 -3

(%)

CBR(%)

(kgf/cm

2)

(cm

)

H(cm)

OPMC 6 BaseCourse

39.2 237,536

0.578 611 454,663 29.5 35

OPMC 4 Subbaseor

Shoulders

13.8 36,717 0.563 245 26,085 - -

(Nil) NaturalGravel

CappingLayer

7.4 1,437 0.0151

30 1,362 39 90

NOTES: 1. OPMCL6: - 50:25:25:6:4% being Ratio of Natural Gravel:Aggregate:Cement:Lime 1. OPMCL4:- 100:4:2% being Ratio of Natural Gravel:Cement:Lime 2. The Ratio of Cement and Lime is aginst 100% of the geomaterial measured by volume.


31/37


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Fig. 12.1.6 Graph Depicting Depreciation Curves of Serviceability Level vs. periodof Cumulative Loading.

12.2 Structural Soundness Under Normal Loading Conditions12.2.1 Analysis of Direct Surcharge Only The extent and effect of surcharge loading on the subgrade was evaluated by applyingEquation 7.20, where the surcharge pressure sc = 53.8kPa then:

7.158.53ln98.4s = %15.4

This implies that the swell in the swampy areas will be contained effectively.

12.2.2 Analysis of Surcharge and Dynamic Loading The surcharge and dynamic loading analysis was carried out in section 12.1.2. 12.3 Structural Soundness Under Critical State ConditionsThe structural soundness of the pavement structure under Critical State Conditions, wherebyall factors contributing to the deterioration of the pavement are within extreme boundary limits,was analyzed and the results are summarized in Tables, while the correspondingcharacteristic curves are depicted in figures.

Without Any Maintenance Scenario

The case whereby NO maintenance isundertaken is presented in Fig. 12.3.1.It can be noted that in this case the pavementstructure deteriorates rapidly after the thirdyear attaining a critical state that requiresresurfacing after only 4 years.

With Maintenance Scenario In this case it is considered that periodicmaintenance and resurfacing will be

implemented accordingly. Also refer toChapter 10.The requirements are presented in Fig. 12.3.2.

Fig. 12.3.1 Effect of Time progression (Nt) onDepreciated Structural Capacity factor

Without Any Maintenance Scenario


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13. CONCLUSIONS

Comprehensive testing and analyticalmethods were employed in this Study inorder to realize the most Value Engineeringbased solution for the pavement structure ofthe Juba River Port Access Road in JubaTown, Central Equatoria State of SouthernSudan.

From both the laboratory and fieldtests results analyzed and discussed inChapter 5 and summarized in Chapter 7 ofthe Engineering Report No. SST1 of May2007, it can be concluded that the designproposed in this Engineering Report isadequate for the project pavement structureprovided that the construction is undertaken in accordance with the Standard, Technical, andParticular Specifications as well as the stipulations in the Method of Construction.

Furthermore, in all the cases considered, and as can also be observed from theconcluding tables and figures presented in the various chapters, it was derived that theOptimum Mechanical and Chemical (OPMC) stabilizing method was effective in enhancingthe vital engineering properties of the geomaterials adopted as well as the compositepavement structure. Fundamentally, this method was quite effective in;

1. Retaining a substantial proportion of their strength even with increasedsaturation levels.

2. Reducing tremendously the surface deflection of the layers under loading.3. Increasing resistance to erosion due to the scouring effect of water flow.4. Increasing resistance to contamination by materials in underlying or

supporting layers that are not stabilized.5. Increasing the effective elastic moduli of the composite pavement structure.6. Realizing an acceptable cost-effective design.

The OPMC stabilization technique, developed on the basis of a new approach, wasdetermined to be the most cost-effective and value engineering based method in respect to all

prevalent conditions considered. It is envisaged to be an interesting structure in terms of CaseStudy Analysis and Research for further development as an effective countermeasure forlandslides, foundations, slope stability, embankment and pavement structure design andconstruction.

Fig. 12.3.2 With Maintenance Scenario


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ACKNOWLEDGMENTSThe author is highly indebted to the contributions of Professor Fumio Tatsuoka and theUniversity of Tokyo. Sincere appreciation is also expressed to the Japan InternationalCooperation Agency (JICA), Japan Bank of International Cooperation (JBIC), ConstructionProject Consultants Inc., Kajima Corporation and Kajima Foundation for funding thesubsequent part of the study conducted in Africa. The authors wish to express their sincereappreciation to the Japan International Cooperation Agency (JICA), Japan Bank of InternationalCooperation (JBIC), Construction Project Consultants Inc., Kajima Corporation and Kajima Foundationfor funding most of the study. The paper would certainly not have been completed without the crucialsupport of Ms. Piera Cesaroni, and the input of Kenneth Wambugu, Ms. Zekal Ketsella, Joram Okado,Paul Kinyanjui, Bryan Otieno, Walter Okello, and Anthony Ngigi. It is also important to mention thecooperation and assistance extended by the Ethiopian Roads Authority as well as the Ministry ofRoads, Public Works and Housing, Kenya.

MAIN REFERENCESAmpadu, S.K (1988): The influence of initial shear on undrained Behaviour of normally consolidated Kaolin,

Master Thesis, University of Tokyo.Bejerrum, L., 1993. Problems of soil mechanics and construction on soft clay and structurally unstable soils

(collapsible, expansive and other). In Proc. 8 th Int. Conference on SMFE, Moscow. P111~159. Blyth, F.G.H., & de Freitas M.H>(1998) A Geology for Engineers 7 th Edition. Arnold, A member of Hodder

Headline Group LONDON. SYDNEY. AUCKLAND. Bulletin of Earthquake Resistant Structure ResearchCentre No. 27 1994. dependence on Frequency of the Failure process of a slope Made up of CoarseParticles. K. Konagai and T. Sato. Institute of Industrial Science University of Tokyo.

Burland, J.B. and Wroth, C.P., (1974) Review Paper : Settlement of buildings and associated damage, inProceeding of the Conference on Settlement of Structures, Pentech Press, Cambridge, 1974. pp.611~654

Burland, J.B., Borroms, B.B., and De Mello, V., (1977) Behaviour of foundations and structures Proceedings ofthe 9 th International Conference on Soil Mechanics, Tokyo, 1977, Session 2

Burland, J.B (1990); On the compressibility and shear strength on clays and shades at constant water content,Geotechnique, Vol. 2, PP,251.

Construction Project Consultant (1995). Tana Basin Road Development Project, Phase II Materials Report Vo. 3

Construction Project Consultant Inc., May, 2000, Hydrological Review and Analyses for Hydraulic Design ofBridge and Major Culvert Structures and Determination of Areas of Protection, Volume I & II, Tana BasinRoad Project Phase II

Construction Project Consultant Inc., July, 2000 Engineering Report on the Design and Construction ofReinforced Earth Embankments (The Terre Armee Method), Tana Basin Road Project Phase II.

Construction Project Consultant, 2001a. A Brief Report on the Computation of Capping Layer Thickness withReference to Native Subgrade Bearing Capacity, CPC Internal Report

Construction Project Consultants, 2001b. Analysis And Evaluation of the Structural Capacity and ServiceabilityLevel of the Existing Road Pavement (Phase III), CPC Internal Report

Construction Project Consultants, 2001c. Characterization of Black Cotton Soil as a Pavement Foundation

Material Based On Comprehensive Analysis (Stage 1), CPC Internal Report CPC Consultants. Tana Basin Road Development Project, Phase II. Materials Report Vol. 3 Tatsuoka, F. &Shibuya, S. Report of the institute of industrial science the University of Tokyo Vol. 37 No. (serial No.235) (1992) Deformation Characteristics of soils and Rocks from Field and Laboratory Tests

Gidigasu. M.D. 1974a. Review of Identification of Problem Laterite Soils in Highway engineering, TransportResearch Board, Washington Recording, I, 497:96~111

Gidigasu. M.D. 1988. Potential application of engineering pedology in shallow foundation engineering on tropicalresidual soils. In Geomechanics in Tropical Coils. Proc. of the II Intl Conference on Geomechanics inTropical Soils, Singapore, 1,17~24.

Gono, k., Mukabi, J.N., Koishikawa, K., Hatekayama, R., Feleke G., Demoze W., Zelalem A., (2003a).Characterization of Some Engineering Aspects of Black Cotton Soils as Pavement Foundation Materials,to be published in the proceedings of the International Civil Engineering Conference on Sustainabledevelopment in the 21st Century.

Hansen, J. Brinch, (1968) A revised extended formula for bearing capacity, Danish Geotechnical Institute Bulletin No. 28 and code of Practice for Foundation Engineering Danish Geotechnical Institute Bulletin No. 32 (1978)


35/37


Hardin, B.O and Drnevich, V.P. (1972), Shear-modulus and damping in soils : measurement and parametereffects, Journal of the Soil Mechanics and Foundations Division, ASCE, Vol. 98, No. SM6:603-624

Horii, N., Toyosawa, Y.& Ampadu, S.K Undrained shear characteristics of soft clay after cyclic loading .pp.113~118.Housner, G. W.: The Behaviour of Inverted Pendulum Structures During Earthquakes, Bull. ofthe Seismological Society of America, Vol. 53, No. 2, pp. 403-417, 1963.

Honsen, J. Brinch, (1961) A general formula for bearing capacity, Danish Geotechnical Institute Bulletin No. 11Imad L.Al-Qadi, Gerardo W. Flintsch, Amara Loulizi, Samer Lahouar & Walid M. Nassar Pavement

Instrumentation Responses at the Virginia Smart Road. IRF Road World Congress, Paris, June 2001. Japan Road Bureau, Japan. 1993. In Road Design Manual, Vol . I (in Japanese).Jardine, R.J. 1985. Investigations of pile-soil behaviour, with special reference to the foundation of offshore

structures. PhD Thesis, University of London.JICA Study Team, 1999. The Study on Rural Roads Improvement In Western Kenya-Materials Testing Analyses

and Countermeasures for Design Purposes, Feasibility Study by The Government of Japan And The Government of Kenya. Jardine, R.J. (1995): One perspective of the pre-failure deformationcharacteristics of some geomaterials, IS Hokkaido 94,2,pp.855 -885.

Kensetsu Kaihatsu, Juba River Port Access Road Design A Comprehensive Engineering Report on the Study,Design and Method of Construction Engineering report No. SST1

Konagai 1 Kazuo and Sato 2 Takeshi. Dependence on Frequency of the Failure Process of Slope Made up ofcoarse Particles. pp. 33~39

K.J. McManus, G. Lu and D. Ruan, The Effects on a Bridge Superstructure of Dynamic Loads Generated by

Long Wavelength Roughness in Road Surfaces. IRF Road World Congress, Paris, June 2001.Meyerh of, G.G., (1963) some recent research on bearing capacity of foundations, Canadian Geotechnical Journal, 1, 16-26.

Ministry of Transport & Public Works, Kenya, 1981. Materials and Pavement Design for New Roads. In Road Design Manual Part III.

Ministry of Public Works & Housing Republic of Kenya, March 1999. Report to OECF Appraisal Mission for the Additional Loan to Tana Basin Road Project in the Republic of Kenya, Volume I & II.

Mukabi, J.N.(1991): Behaviour of clays for a wide range of strain in Triaxial compression, Msc. Thesis, Universityof Tokyo.

Mukabi, J. N. (1995): Deformation Characteristics of small strains of clays in triaxial tests PhD Thesis, Univ. ofTokyo. Mukabi, J.N. (1998):Con-Aid Research and Development Proposal.

Mukabi.,J.N., Murunga P.A, Wambura.J.H. & Maina J.N., Behaviour of con-Aid treated fine grained Kenyan soils.Geotechnics for Developing Africa, Wardle, Blight & Fourie (eds) 1999 Balkema, Rotterdam, ISBN 90

809 082 5.pp.583~519.Mukabi J.N & Tatsuoka, F. 1995. Effects of swelling and saturation of Unsaturated Soil Behaviour andApplications, Int. Symposium on the Behaviour of Unsaturated Soils, University of Nairobi, Nairobi,Kenya.

Mukabi J.N & Tatsuoka, F., Kohata, Y. & Akino, N. 1994b. Small strain stiffness of Pleistocene clays. Proc.Int.Symp. on pre-failure Deformation Characteristics of Geomaterials, IS-Hokkaido . 94 Balkema, Vol. 1,PP. 189-195

Mukabi J.N & Tatsuoka, F. (1992); Effects of consolidation stress ratio and strain rate on the peak stress ratio ofKaolin, the 27 th Annual meeting of the JSSMFE, Kochi, PP.655~6

Mukabi J.N. & Tatsuoka, F. (1994); Small strain behaviour in triaxial compression of lightly over consolidatedKaolin, proc. 49 th Annual Conf. Of JSCE, III, pp.296~297Mukabi J.N & Tatsuoka, F. 1999. Effects ofstress path and ageing in reconsolidation on deformation characteristics of stiff natural clays. Proc. 2 nd I.S on pre-failure characteristic of geomaterials, Torino.

Mukabi, J.N 1999. The Study on Rural Roads Improvement in Western Kenya Materials Testing Analyses andCountermeasures for Design Purposes. In Internal Reports and Correspondence , Japan InternationalCooperation Agency (JICA) & Ministry of Roads & Public Works, Kenya.

Mukabi, J.N. 2000. The design and construction of Reinforced Earth Embankments. In Internal Reports and Correspondence, The Terre Armee Method, 2000. CPC, Nairobi.

Mukabi, J.N & Tatsuoka, F. 1994, 1999. Small strain behaviour in triaxial compression of lightly over-consolidated Kaolin. In Proc. 49 th Annual Conf. of JSCE , III: 286-297. Influence of reconsolidation stresshistory and strain rate on the behaviour of kaolin over a wide range of strain. In Wardle, Blight & Fourier(eds), Geotechniques for Developing Africa: Proc. 12 th African Regional Conf. ISSMGE Durban, 1999. Balkema, Rotterdam.

Mukabi, J.N. 2001a. Theoretical and empirical basis for a method of determining the optimum batching ratio formechanical stabilization of geomaterials. In Proc. 14 th IRF road World Congress, Paris, June 2001.

Mukabi, J.N & Shimizu, N. 2001b. Strength and deformation characteristics of mechanically stabilized roadconstruction materials based on a new batching ratio method. In Proc. 14 th IRF Road World Congress,Paris, June 2001.


36/37


Mukabi, J.N. Njoroge, B.N. & Toda, T. 2001c. pragmatic method of evaluating design parameters adoptingKenyan tropical soils for pavement structure, In Procl 4 th IRF Road World Congress, Paris, June 2000.

Mukabi, J.N, 2001d. Derivation and application of consolidation and shear stress ratio functions with reference toCritical State analysis of N.C clays. In Proc. ISSMGE Istanbul International Conference. August 2001.

Mukabi, J.N., 2002c. Some Recent Advances in highway and bridge foundation engineering, Seminar for

Ethiopian Roads Authority and Japan Overseas Development Assistance Ethiopia. Mukabi, J.N., Gono K., Koishikawa K., Feleke G., Hatekayam H., Demoze W., R., Kunioka H., Zelalem A.,(2003a). Innovating Modified NDT/DT Techniques for the Evaluation of An Existing Pavement Structure-Method of Testing, published in the proceedings of the International Civil Engineering Conference onSustainable development in the 21 st Century.

Mukabi, J.N., Gono K., Koishikawa K., Feleke G., Hatekayam R., Demoze W., Kunioka H., Zelalem A., (2003b).Innovating Modified NDT/DT Techniques for the Evaluation of An Existing Pavement Structure-Theoretical Considerations and Experimental Results, published in the proceedings of the InternationalCivil Engineering Conference on Sustainable development in the 21 st Century.

Mukabi, J.N., Feleke G., Demoze W., Zelalem A., (2003c). Impact of Environmental Factors on thePerformance of Highway Pavement Structures, published in the proceedings of the International CivilEngineering Conference on Sustainable development in the 21 st Century.

Mukabi, J.N., (2003d). The Role of Enhanced Research Oriented Highway and Foundation Design for

Sustainable Development, published in the proceedings of the International Civil EngineeringConference on Sustainable development in the 21 st Century.Mukabi, J.N., (2005a). Some Vital Engineering Aspects of The Consultancy Completion Report of the Addis

Ababa~Goha Tsion International Trunk Road, A JICA Study.Newill, R.J. (1961). A Laboratory Investigation of Two Red Clays from Kenya, Geotechnique, 11(4)

302~318.Pandian, N.S., Nagaraj, T.S. & Sivakumar Banu, G.L (1993). Tropical Clays, Part II.Engineering behaviour. J. Geotech. Engrag., ASCE.

Peck, R.B., Hanson, W.E. & Thornburn, T.H 1967. (2 nd ed) Foundation Engineering, 271-276. New York, JohnWiley.

Richart, Jr., F.E. (1977); Dynamic stress-strain relationships for soils, S-SO-A ,Proc. Of 9 th ICSMFE, Tokyo, 3,pp.189-195.

Road Research. Catalogue of road surface deficiencies. 1978 Organization for economic cooperation anddevelopment. Road Research Institute. MOC, Japan. 1990 Specifications for road and bridge design,

Vol. I & IV. (in Japanese) Road Research Laboratory, 1970. A guide to the structural design of pavements for new road. Road Note No.29.

Road Transport Research. Pavement Management Systems. Paris, 1987 Organization for economic cooperationand development.

Skempton, A.W and MacDonald, D.H. (1956), The allowable Settlement of buildings, Proceedings, of theInstitution of Civil Engineers, part 3, 5, 727-784

Savage, P.F. & Leou, J. (1998). Guidelines on Use of CON-AID Liquid Chemical Stabilizer.Savage, P.F. (1998). Some Experiences on the Use of Con-Aid: A Water-Soluble Ionic Additive, University of

Pretoria. Tatsuoka Fumio, Lo Presti Diego and Kohata Yukihiro, April 2-7, 1995, Third InternationalConference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics.

Shultze, E. and sheriff, G., Prediction of Settlement from evaluated settlement observations for sand,Proceedings of the 8 th International Conference on Soil Mechanics, Moscow, 1973, Vol. 1, pp. 225.

Tatsuoka, F, Jardine, R. J., Lopresti, D., Benedetto, D. H. and Kodaka, T. (1997). Characterizing the pre-failureDeformation Properties of Geomaterials, Theme lecture ICSMFE, Hamburg, vol. 4. pp.2129-2164.

Tatsuoka, F. 1992 Roles of facing rigidity in soil Reinforcing, Theme Lecture for International Symposium,Kyushu, Japan.

Tatsuoka, F, Jardine, R. J., Lopresti, D., Benedetto, D. H. and Kodaka, T. (1999). Characterizing the pre-failureDeformation Properties of Geomaterials, Theme lecture ICSMFE, Hamburg, 1997, vol. 4. pp.2129-2164.2,pp.947-1063.

Tatsuoka, F. and Kohata, Y. (1995): Stiffness of hard soils and soft rocks in engineering applications, KeynoteLecture, IS- Hokkaido 94,Vol.

Terzaghi, K. & Peck, R.b 1967. (2 nd ed) So il Mechanics in engineering practice, 310 . New York, John Wiley.

Towhata, I., Kawasaki, Y., Harada, N. & Sunaga, M. Contraction of soil subjected to traffic-type stressapplication. Proc. Int. Symp. On Pre-failure Deformation Characteristics of Geomaterials, IS-Hokkado94, Balkema Vol. 1, pp. 305~310.

Transport and Road Research Laboratory. 1977. A guide to the structural design of bitumen surfaced roads intropical and sub-topical countries. Road Note No. 31Vanghn, P.R. 1985. Geotechnical Characteristics of


37/37

residual soils. In J. Geotech. Engrg. ASCE, III(1) 77~94. Yoder, E.J & Witczak, M.W; (1975). Principlesof Pavement Design Second Edition, A Wile-Interscience Publication-John Wiley-Sons, Inc.

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