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SPECIAL PUBLICATION No. 08.2.34 February, 2012
HANDBOOKOF
GEOTEXTILES
THE BOMB Y TEXTILE RESE RCH SSOCI TION
L.B.S. MARG, GHATKOPAR (W), MUMBAI - 400086TEL. : 022-25003651 / 2652
EMAIL : [email protected] : www.btraindia.com
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ISBN 978-81-7674-132-3
© 2012 THE BOMBAY TEXTILE RESEARCH ASSOCIATION
All rights reserved. No part of this
publication may be reproduced or used inany form, whatsoever without the writtenpermission from the publisher
Published by :
THE BOMB Y TEXTILE RESE RCH SSOCI TION
L.B.S. MARG, GHATKOPAR (W), MUMBAI - 400086TEL. : 022-25003651 / 2652Fax : 022 -25000459EMAIL : [email protected] : www.btraindia.com
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PREFACE
Geotech sector is one of the rapidly growing sectors of Indian technical textile industry. Estimates of
around 15-20% growth per annum are often talked about, for the next few years. This is obvious
because of the large number of projects that are on-going and in the pipeline in various parts of the
country, coupled with active role being played by the Ministry of Textiles; Government of India in
promoting these knowledge based textile products. The Centre of Excellence (COE) for Geotech set
up by the government of India at Bombay Textile Research Association (BTRA), Mumbai, is one of
the series of steps in this direction.
At BTRA, a state of the Art accredited Geotech lab is functioning which caters to testing needs as per
national and international standards. A Resource centre with an excellent collection of reference
materials, standards and specifications are available for those interested.
One of the bigger hurdles in use of geotextiles in India is lack of awareness on all aspects of utility of
these products by the construction engineers. While attempts of creating awareness on the
application potential of geotextiles is being made by various agencies, one handicap that needed
attention was the absence of critical information on raw materials, manufacturers and their
products, range of products available, application areas, potential users of geotextiles, test facilities
within national and international accreditation and this was a great constraint. When this point was
discussed at a meeting of Indian Technical Textile Association (ITTA) (a body of all those who
interested in promotion of technical textiles), BTRA was entrusted with the task of bringing out a
suitable guide book for this industry. Hence this handbook is an attempt to address the long felt
need of Geotech industry. This handbook is based on the knowledge and experience of
manufacturers, raw material suppliers and other nodal agencies. The handbook is being circulated
as a part of our long-term goal of enhanced usage of geotextile in infrastructural projects and we
hope will be a ready reckoner for all stockholders of the industry.
This handbook is result of sustained efforts of Mr Vitin Gupta, Mr V Kannan of Reliance Industries
Ltd and Mr Amol Shivdas of BTRA to whom our thanks are due.
Dr. A N Desai
Mumbai Director
Date: 12th February, 2012 BTRA
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TABLE OF CONTENTS
1. Introduction ---------------------------------------------------- 1
2. Functions ------------------------------------------------------ 7
3. Application matrix----------------------------------------------10
4. Geotextiles in Roads -------------------------------------------11
5. Case studies on usage of Geotextiles in Roads --------------- 31
6. Jute Geotextiles ----------------------------------------------- 47
7. Case studies on Jute Geotextiles in Roads--------------------51
8. Geotextiles in Erosion control --------------------------------- 55
9. Case Studies - Geotextiles In Erosion Control --------------- 59
10. Polymer Gabions in Erosion Control ---------------------------73
11. Case studies on Polymer Gabions in Erosion Control--------- 77
12. Geobags and Geotubes for Erosion control -------------------83
13. Case studies - Geotubes in erosion control -------------------91
14. A few geosynthetics products ---------------------------------99
15. Geogrids -------------------------------------------------------- 101
16. Case studies on Geogrids ------------------------------------- 107
17. Prefabricated Vertical Drains ----------------------------------115
18. Miscellaneous case studies ------------------------------------ 117
19. International Case studies ------------------------------------- 123
20. Standards on geotextiles -------------------------------------- 14121. Properties and Testing of Geotextiles ------------------------ 145
22. Profile of few Indian Geotextiles Manufacturers -------------161
23. Appendices -------------------------------------------------169
I. Indian Govt supports covering COEs---------------------- 171
II. Associations for Geotextiles ------------------------------172
III. List of Nodal agencies in India ---------------------------173
IV. List of NHAI consultants----------------------------------- 176
V. List of NHAI contractors ----------------------------------179
24. References -------------------------------------------------185
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1. INTRODUCTION
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1. INTRODUCTIONGeosynthetics wherein geotextile is a part are, used in a wide variety of applications for
infrastructure projects like Roads, River & Sea Bank Protection, Canal Lining, Landfills,Airport taxiways etc. In broad terms there are around 9 categories of Geosynthetics.
1 Geotextiles2 Geogrids3 Geonets4 Geomembranes5 Geosynthetic Clay Liners
6 Geofoam7 Geocells8 Drainage / Infiltration Cells9 Geocomposites
Geotextile is any permeable textile material used with foundation, soil, rock, earth, or
any other geotechnical engineering related material as an integral part of a man-madeproduct, structure, or system.
Geotextiles forms one of the largest groups of geosynthetic material. Its functions andproperties are deeply studied, so now it is widely accepted and used in various areas of
geotechnical structures. Most important factor that makes it prominent is its longer lifeand resistance to biodegradation because of its synthetic fiber content rather thannatural content like Jute, cotton, wool, or silk. Unlike natural fibers like cotton, jute etc
synthetic fibers which are constituent of geosynthetics, have higher strength and notprone to degradation under soil condition and hence have longer life. The syntheticfibers are made into porous structures of woven, non woven or knitted. The original
term used for geotextiles, and still sometime used is filter fabrics. This is because of the
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fact that geotextiles are porous to liquid flow across their manufactured plane and alsowithin their thickness.
Literature available shows that geotextiles have been effectively used outside India since
1950. Paper entitled as “Use of Plastic Filters in Coastal Structures”, proceedings from
the 16th International Conference Coastal Engineers, Tokyo, by Barrett, R.J., describes
the work originating in late 1950s using geotextiles behind precast concrete seawalls,under precast concrete erosion control blocks, beneath large stone riprap, and in other
erosion control situations.
In the late 1960s Rhone-Poulenc Textiles in France worked on use of nonwoven needlepunched fabrics for unpaved roads, beneath railroad ballast, within embankments and
earth dams. Main emphasis was on the functions like separation and reinforcement but itwas recognised that fabric can also transmit water within the plane of their structure,acting as drains. This drainage function of geotextile leads to various other usages like
dissipation of pore-water pressures, and horizontal and vertical flow interceptors. So
today geotextiles is well recognised for all these functions.
As per the Ministry of Textile, Government of India, Current Geotextiles Market in India
(Imports and domestic production) as per 2007-08 is around Rs 272 Crore, comprisingimports of an estimated Rs 105 Crore and domestic production of around Rs 167 Crore.
In terms of product category, the market includes Rs 241 Crore of synthetic woven/non-
woven Geotextiles (85 Crore of woven and 67 Crore of Non-woven) as well as otherproducts like Geogrids and Others (Geomembranes, Geonets and Geocomposites). Agro-based Geotextiles (made of Jute and Coir) are also developing and finding acceptance as
a class of products. Market size for these products was around Rs 31 Crore. The
domestic market has shown a healthy growth rate of 15-18% on YOY basis as per theindustry estimate.
Geotextile Structures
There are two principal geotextile types, or structures:wovens and nonwovens. Other manufacturingtechniques, for example knitting and stitch bonding are
occasionally used in the manufacture of specialty
products.
Early laying of Geotextiles in India
Non Woven Geotextile
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Nonwovens: Nonwoven geotextiles are manufactured from either staple fibers (staplefibers are short, usually 1 to 4 inches in length) or continuous filaments randomly
distributed in layers onto a moving belt to form a felt-like "web". The web then passesthrough a needle loom and/or other bonding machine interlocking the fibers/filaments.Nonwoven geotextiles are highly desirable for subsurface drainage and erosion control
applications as well as for road stabilization over wet moisture sensitive soils.
Wovens: Weaving is a process of interlacing yarns to makea fabric. Woven geotextiles are made from weavingmonofilament, multifilament, or slit film yarns. Slit film
yarns can be further subdivided into flat tapes andfibrillated (or spider web-like) yarns. There are two steps in
this process of making a woven geotextile: first,
manufacture of the filaments or slitting the film to createyarns; and second, weaving the yarns to form the
geotextile. Slit film fabrics are commonly used for sedimentcontrol, i.e. silt fence, and road stabilization applications
but are poor choices for subsurface drainage and erosion control applications. Thoughthe flat tape slit film yarns are quite strong, they form a fabric that has relatively poor
permeability. Alternatively, fabrics made with fibrillated tape yarns have betterpermeability and more uniform openings than flat tape products.Monofilament wovens have better permeability, making them suitable for certaindrainage and erosion control applications. High strength multifilament wovens are
primarily used in reinforcement applications
Polymers Gabions: Polymer Gabions are rectangular orcylindrical baskets fabricated from polymer meshes andusually filled with stone and used for structural purposes
such as retaining walls, revetments, slope protection, andsimilar applications
Geogrids: A geogrid is geosynthetic material used toreinforce soils and similar materials. Geogrids arecommonly used to reinforce retaining walls, as well as sub-
bases or subsoils below roads or structures. Soils pull apart
under tension. Compared to soil, geogrids are strong intension.
Geobags: Geobags are sand-filled high-strength geotextilebags available in the various sizes and are used in
riverbank, beach protection, and offshore breakwaters.
Polymer Gabion
Geogrids
Woven Geotextile
Geobags
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Geotubes: Geotextile tubes are large tube likestructures fabricated from high strength geotextile
with soil-in-fills. Geotextile tube is formed in situ bythe hydraulic pumping of local soil into theprefabricated geotextile tube. This leads to a flexible,
monolithic, continuous structure that is highly
resistant to water currents. Sand is widely used asthe soil in-fill material because of its low
compressibility but other hydraulically pumped soiltypes can be used. Geotextile tubes are normally
characterized in terms of theoretical diameter.
Geocomposites: They combine the best features of different materials in such a waythat specific applications are addressed in the optimal manner and at minimum cost.Thus, the benefit/cost ratio is maximized.
PVDs The prefabricated vertical drain is a long flattube of woven or non-woven geotextile with a coreinside. For construction of structures on sites
underlain by thick strata of soft cohesive soils, amethod of foundation soil improvement is generallyrequired to prevent bearing capacity failure and or toavoid excessive total and differential settlements.
These soft soils have a very low bearing capacity to
due to their saturated state; the PVD’s are used toincrease the bearing capacity of the soil by removing
the excessive water present inside.
Geotextile Polymers
Almost all geotextiles available in the India are
manufactured from either polypropylene orpolyester. Polypropylene is lighter than water
(specific gravity of 0.9), strong and very durable.Polypropylene filaments and staple fibers are used
in manufacturing woven yarns and nonwovengeotextiles. It is preferred as it is inert material
and geotextiles made of polypropylene are inert to
chemical attack and can be used in harsh climaticconditions.
High tenacity polyester fibers and yarns are also used in the manufacturing of geotextiles. Polyester is heavier than water, has excellent strength and creep properties, and is compatible with most
common soil environments. In addition natural fibers like Jutes are also used for geotextiles.
To know about products like geonets, geocells etc readers are encouraged to visithttp://gmanow.com/
Geotubes
PVD
Raw material - Polypropylene
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2. FUNCTIONS
Geosynthetics have six broad functions:
1. Separation2. Reinforcement3. Filtration4. Drainage
5. Barrier6. Protection
Based on these functions geotextiles possesses wide range of applications in various
areas of geotechnical structures.
Separation:
Separation of two dissimilar materials which intend to serve different purposes in such a
way that their integrity and functioning remains intact. This is achieved by placing
flexible porous textile between two dissimilar materials.
When stone aggregates are placed over a subgrade consisting of fine aggregates in
flexible pavement, then there are two possible mechanisms that can take place. One is
that fine soil attempts to enter into the voids of stone aggregate, thereby ruining its
drainage capability; the other is that the stone aggregates attempts to intrude into the
fine soil, thereby deteriorating the stone aggregate strength. This would diminish the
performance of the aggregates as well as the subgrade layer. However, with the use of
geotextiles between these two layers will avoid these mechanisms, leading to
satisfactory performance of both the stone aggregates and subgrade layer.
Without Geotextiles With Geotextiles
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Geotextiles as filter fabric
Geotextiles as drainage layer
Reinforcement
Low strength fine grained silt and clay are good in compression but poor in tension. In
such case, geotextiles materials which are good in tension can recover the deficiency of
low strength soil. Geotextiles reinforcement is defined as synergistic improvement in the
total system strength created by the introduction of a geotextiles into a soil and
developed primarily through the following three mechanisms: One, lateral restraint
through interfacial friction between geotextile and soil/aggregate. Two, forcing the
potential bearing surface failure plane to develop at alternate higher shear strength
surface. And three, membrane type of support of the wheel loads.
Filtration: (Permittivity)
It is defined as “the equilibrium geotextile-
to-soil system that allows for adequate
liquid flow with limited soil loss across the
plane of the geotextile over a service
lifetime compatible with the application
under consideration. Influencing
characteristic of this function is apparent
opening size because to perform this
function the geotextile needs to satisfy two
conflicting requirements: the filter’s pore size must be small enough to retain fine soilparticles and at the same moment it should allow the flow of water perpendicular to the
plane of fabric (Permittivity). The geotextile must also have the strength and durability
to survive construction and long-term conditions for the design life of the drain.
Additionally, construction methods have a critical influence on geotextiles drain
performance. Figure explains the filtration function of geotextile.
Drainage
Drainage refers to the ability of geotextile
whose three-dimensional structure provides
an path for flow of water through the plane
of the geotextile. Thus drainage is defined
as the equilibrium soil-to-geotextile system
that allows for adequate liquid flow with
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Geotextiles as barrier
limited soil loss within the plane of the geotextiles over a service lifetime compatible
with the application under consideration. Above figure also illustrates the Transmissivity
function of geotextile.
Barrier (Sealing) Function
A geotextile performs this function when
impregnated with asphalt or other
polymeric mixes rendering it relatively
impermeable to both cross-plane and in-
plane flow. In this function geotextile is
placed on the existing pavement surface
following the application of an asphalt tack
coat. The geotextile absorbs asphalt to
become a waterproofing membrane
minimizing vertical flow of water into the pavement structure.
Protection (Cushion) Function
A geotextile can be used in any landfill project for properly protecting the geomembrane
from tearing or puncturing during construction. Research indicates that a properly
selected nonwoven, needle-punched geotextile cushion installed above and/or below the
geomembrane can effectively protect it from construction and operational damage.
Geotextiles as protection
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3. APPLICATION MATRIX
Category Sub-Category Functions Potential/ Chartpresentation
NEW ROADS -
BELOWSUBGRADE
REINFORCEMENT
SEPARATION
DRAINAGE
ROADS
OLD ROADS-
PavementInterlayer- topreventreflectivecracking
REINFORCEMENT
MOISTUREBARRIER
RIVER BANKS
EMBANKMENTPROTECTION
FILTER FABRIC
SEA EROSIONCONTROL
As Geotubes for
Protection
Geotube
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4. GEOTEXTILES IN ROADS
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4. GEOTEXTILES IN ROADS [1]
A large variety of detrimental factors affect the service life of roads and pavements
including environmental factors, subgrade conditions, traffic loading, utility cuts, road
widening, and aging. These factors contribute to an equally wide variety of pavement
conditions and problems which must be addressed in the maintenance or rehabilitation
of the pavements, if not dealt with during initial construction. Pavement maintenance
treatments are often ineffective and short lived due to their inability to both treat the
cause of the problems and renew the existing pavement condition. The main cause of
distress in pavements is that they are quite permeable with 30 to 50% of precipitation
surface water infiltrating through the pavement, softening and weakening the pavement
subgrade and base, accelerating pavement degradation. Existing pavement distress such
as surface cracks, rocking joints, and subgrade failures cause the rapid reflection of
cracking up through the maintenance treatment.
Therefore, the preferred strategy for long-term road and pavement performance is to
build in safeguards during initial construction. These performance safeguards include
stabilizing the subgrade against moisture intrusion and associated weakening;
strengthening road base aggregate without preventing efficient drainage of infiltrated
water; and, as a last resort, enhancing the stress absorption and moisture proofing
capabilities of selected maintenance treatments. Geotextiles are the most cost-effective
tools for safeguarding roads and pavements in these ways.
The four main applications for geotextiles in roads are subgrade separation and
stabilization, base reinforcement, overlay stress absorption, and overlay reinforcement.
Subgrade stabilization and base reinforcement involve improving the road structure as it
is constructed by inserting an appropriate geotextile layer.
Subgrade separation and stabilization applies geotextiles to both unpaved and
paved roads.
Base reinforcement is the use of geotextiles to improve the structure of a pavedroad. Geotextiles are also helpful in rehabilitating distressed road surfaces.
The application of a layer of asphalt concrete called an overlay is often the
solution for damaged pavement. Geotextiles can be used as interlayers by placing
them below or within the overlay. Some geotextiles relieve stress and others are
able to reinforce the overlay. The products may also provide a moisture barrier.
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Though only widely recognized since the latter half of the 1900s, these
advantages were initially demonstrated as early as the 1930’s using conventional
textile materials.
4.1 SUBGRADE SEPARATION AND STABILIZATION
Introduction to the Problem
Temporary roads used for hauling and access roads that are subject to low volumes of
traffic are often constructed without asphalt or cement concrete surfacing. In these
cases, a layer of aggregate is placed on the prepared subgrade of these roads to
improve their load carrying capacity. Problems are usually encountered when the
subgrade consists of soft clays, silts and organic soils. This type of subgrade is often
unable to adequately support traffic loads and must be improved.
Typical Solutions
Excavating and replacing unsuitable materials is costly and time consuming. Other
methods of subgrade improvement include deep compaction, chemical stabilization and
preloading.
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The Geotextile Solution
Geotextiles are proving to be a cost effective alternative to traditional road construction
methods. As a result, the application of geotextiles to the construction of unpaved roads
over soft subsoils has become quite popular. Design has focused on the stabilization of
the subgrade and the reinforcement of the aggregate, leading to the identification of two
important functions: membrane action and lateral restraint. Membrane action is the
ability of a geotextile material to reduce and spread stress arising from the weak
subgrade. Lateral restraint, sometimes called confinement, is the lateral interaction
between the aggregate and the subgrade with the geotextile. The presence of the
geotextile restrains lateral movement of both the aggregate and the subgrade,
improving the strength and stiffness of the road structure.
Separation
At small rut depth, the strain in the geotextile is also small. In this case, the geotextile
acts primarily as a separator between the soft subgrade and the aggregate. Any
geotextile that survives construction will work as a separator.
Stabilization
For larger rut depths, more strain is induced in the geotextile. Thus the stiffness
properties of the geotextile are essential. A considerable reduction in aggregate
thickness is possible by the use of a geotextile having a high modulus in the direction
perpendicular to the road centerline; however, the benefits of the geotextile are not
wholly dependent on the membrane action achieved with a stiff geotextile. Lateral
restraint produced by the interaction between the geotextile and the aggregate is
equally important. The following general conclusions can be drawn relating to a typical
road base.
A geotextile element that functions primarily as a separator (typically when the
subgrade CBR ≥3) will increase the allowable bearing capacity of the subgrade by
40 to 50 percent. ((separation geotextiles) A geotextile element that functions primarily to provide confinement of the
aggregate and lateral restraint to the subgrade (typically when the subgrade CBR
< 3) will both increase the allowable bearing capacity of the subgrade and
provide an improved load distribution ratio in the aggregate. The combined
benefits can enhance load carrying capacity of the road by well over 50 percent.
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With very weak subgrades, it is often beneficial to combine the benefits of both
separation and stabilization.
Design for Stabilization
The design of geotextile-reinforced unpaved roadways has been simplified into design
charts that relate aggregate thickness requirements to a range of subgrade strengths,
based on standard highway design loading and various allowable rut depths.
BASE REINFORCEMENT
Introduction to the Problem
Permanent roads carry larger traffic volumes and typically have asphalt or port-land
cement concrete surfacing over a base layer of aggregate. The combined surface and
base layers act together to support and distribute traffic loading to the subgrade.
Problems are usually encountered when the subgrade consists of soft clays, silts and
organic soils. This type of subgrade is often water sensitive and, when wet, unable to
adequately support traffic loads.
If unimproved, the subgrade will mix with the road base aggregate – degrading the road
structure - whenever the subgrade gets wet.
Typical Solutions
As with unpaved roads, a problematic subgrade is typically excavated and replaced, or it
is improved by the addition of cement, lime, or excess aggregate. In any case, the
traditional solution is often costly and always time consuming.
The Geotextile Solution
As was noted earlier, geotextiles are proving to be a cost effective alternative to
traditional road construction methods. In paved roads, lateral restraint also called
confinement is considered to be the primary function of the geotextile. With the addition
of an appropriate geotextile, the Soil-Geotextile- Aggregate (SGA) system gainsstiffness. The stiffened SGA system is better able to provide the following structural
benefits:
Preventing lateral spreading of the base
Increasing confinement and thus stiffness of the base
Improving vertical stress distribution on the subgrade
Reducing shear stress in the subgrade
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INSTALLATION OF GEOTEXTILES FOR SEPARATION, STABILIZATION,
AND BASE REINFORCEMENT
1. Site Preparation
Clear and grade the installation area. Remove all sharp objects and large stones. Cut
trees and shrubs flush with the subgrade. Removal of topsoil and vegetation mat is
not necessary, but is recommended where practical. Excessively soft spots or voids
may be unsuitable for geotextile installation. Fill these areas with select material and
compact prior to geotextile installation. The problem area may be enhanced by using
a geotextile at the bottom of the excavation prior to backfilling.
2. Deployment of the Geotextile
Unroll the geotextile on the prepared subgrade in the direction of construction traffic.
Hold the geotextile in place with pins, staples, fill material or rocks. Adjacent rolls
should overlap in the direction of the construction. Depending on the strength of the
subgrade, the overlaps may have to be sewn.
3. Placement of the Aggregate
Place the aggregate over firm subgrades by back dumping aggregate onto the
geotextile and then spreading it with a motor grader. For weaker subgrades, dump
onto previously placed aggregate and then spread the aggregate onto the geotextile
with a bulldozer. On weaker subgrades, a sufficient layer of aggregate must be
maintained beneath all equipment while dumping and spreading to minimize the
potential of localized subgrade failure. Avoid traffic directly on the geotextile. When
using construction equipment on the aggregate, try to avoid any sudden stops, starts
or sharp turns. Maintain a minimum lift thickness of 6-inches (15 cm) except in cases
of low volume roads. Compact the aggregate to the specified density using a drum
roller. Fill any ruts with additional aggregate and compact as specified.
DESIGN OF GEOTEXTILE FOR ROAD WAY REINFORCEMENT
Combined use of geotextile (good in tension and poor in compression) and soil (good in
compression and poor in tension) suggests a number of situations in which geotextile
have made existing designs work better.
This section describes the design of unpaved roads; in which soft soil subgrade have
sand or stone aggregate placed directly above. No permanent surfacing, such as
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concrete or asphalt pavement, is immediately placed on the stone. There are many
thousands of kilometres of unpaved secondary roads, access roads, and the like, with
no permanent surfacing on them, At a later time, perhaps years after settlement takes
place and ruts are backfilled, a permanent surfacing may be placed.
Geotextile mobilises tensile strength via deformation of the soil subgrade. Deformation
of the soil subgrade takes place by imposed traffic which causes the subgrade
deformation and hence the geotextile deformation with the development of tensile
properties of geotextile. How much deformation is necessary with regard to vehicular
loading, the particular geotextile, the time it takes for adequate strength mobilisation,
and so on, are all pressing questions, but the deformation characteristics of the soil
takes the precedence. A soft, yielding soil subgrade is needed to mobilise the geotextile
strength and this is decided on the basis of California Bearing Ratio (CBR) of soil
subgrade. CBR test is done as per ASTM D 1833 or ISO 12236. The CBR value iscomparison of the subgrade soils resistance to the force of a 50 mm diameter plunger at
a given deformation, with that of the standardised crushed stone base material.
For the purpose of using geotextiles in
roadway applications on soil subgrade of
different strength, functions are subdivided
based on the CBR values of the soil
subgrade. This is tabulated as:
Design consists the calculations made for the
thickness of stone required without a
geotextile, then with a geotextile; the difference the thickness of stone that is saved. By
determining the cost of saved stone versus the cost of geotextile, so the value of using
geotextile is known.
Unsoaked Soaked
Separation > 8 > 3
Stabilisation 8-3 3-1
Reinforcement and
Separation < 3 < 1
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GIROUD AND NOIRAYS ANALYTIC METHOD OF DESIGN:
Giroud and Noiray use the geometric model shown in figure for a tire wheel load of
pressure pec on a B X L area, which dissipates through ho thickness of stone base without
geotextile and h thickness of stone base with a geotextile.
The geometry indicated results in a stress on the soil subgrade of po (without
geotextile) and p (with geotextile) as follows
po = + γho (1)
p = + γh (2)
Where,
P = Axle load
γ = unit weight of stone aggregate
Since the pressure exerted by the axle load through the aggregate and into the soil
subgrade is known, the shallow foundation theory of geotechnical engineering can now
be utilised. It is assumed throughout the analysis that the soil is functioning in its
undrained condition. Critical in this design method are the assumptions that without the
geotextile the maximum pressure that can be maintained corresponds to the elastic limit
of the soil, that is,
po = C + γho (3)
With geotextile the limiting pressure can be increased to the ultimate bearing capacity of
the soil, that is,
p* = ( + 2) C + γh (4)
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thus for the case of no geotextile reinforcement, equations (1) and (3) can be solved ,
resulting in equation (5), which yields the desired aggregate thickness response curve
without the use of geotextile:
C = (5)
Where,
C = Soil cohesion
P = axle load
pc = tire inflation pressure
ho = aggregate thickness, and
αo = angle of load distribution
For the case where geotextile reinforcement is used, p* in equation (4) is replaced by (p
- pg), where pg is a function of the tension in the geotextile; hence its elongation is
significant. On the basis of the probable deflected shape of the geotextile-soil system,
pg = (6)
Where,
E = modulus of geotextile,
= elongation (strain),
a = geometric propertyS = settlement under the wheel (rut depth)
Combining equation (2), (4) and (6) and using p* = p - pg, gives equation (7), where h
is unknown aggregate thickness. It can be graphed for various rut depth thicknesses and
various moduli of geotextiles.
( + 2) C = - (8)
With these two sets of equations, the design method is essentially complete, since both
ho (thickness without geotextile) can be calculated. From these two values Δh = h o – h
can be obtained, which represents the savings in aggregate due to presence of the
geotextile.
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4.2 OVERLAY STRESS ABSORPTION AND REINFORCEMENT
Introduction to the Problem
Road surfaces must be maintained regularly. Commonly, a paved road becomes a
candidate for maintenance when its surface shows significant cracks and potholes. The
rehabilitation of cracked roads by simple overlaying is rarely a durable solution. The
cracks under the overlay rapidly propagate through to the new surface. This
phenomenon is called reflective cracking. Cracks in the pavement surface cause
numerous problems, including:
Riding discomfort for the users
Reduction of safety
Infiltration of water and subsequent
reduction of the bearing capacity of the subgrade
Pumping of soil particles through the crack
Progressive degradation of the road structure in the vicinity of the cracks due to
stress concentrations
Typical Solutions
In spite of reflective cracking, overlays are still the most viable option for extending the
life of distressed pavement. To lengthen the lifetime of an overlay, special asphalt mixes
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can be specified. Also, the thicker the overlay the longer it will last. Thick overlays are
expensive as are special asphalt mixes, but the alternative is reconstruction. Depending
on the cause of the problem, this can involve removing layers of pavement, improving
subgrades, and repaving.
This is extraordinarily expensive and time consuming.
The Geotextile Solution
A geotextile interlayer can be placed over the distressed pavement or within the overlay
to create an overlay system. The geotextile interlayer contributes to the life of the
overlay via stress relief and/or reinforcement and by providing a pavement moisture
barrier.
A stress relieving interlayer retards the development of reflective cracks by absorbing
the stresses that arise from the damaged pavement. It also waterproofs pavements that
typically allow 30 to 60% of precipitation to infiltrate and weaken the road structure.
Reinforcement occurs when an interlayer is able to contribute significant tensile strength
to the overlay system. The reinforcement limits the movement of the cracked old
pavement under traffic loads and thermal stress by holding the cracks together.
The benefits of geotextile interlayers include:
Delaying the appearance of reflective cracks
Lengthening the useful life of the overlay
Added resistance to fatigue cracking
Saving up to 2 inches of overlay thickness
INSTALLATION OF INTERLAYERS*
The recommendations provided here are applicable for laying of geotextile (paving
fabric) ,' between, two bituminous layers as part of pavement strengthening to provide a
water resistant membrane and crack retarding layer. It is recommended that paving
fabric should be used over the entire pavement area affected by cracking and not in theform of strips over the pavement cracks.
Step - 1 Preparing the Surface
Before the application of paving fabric, thoroughly
clean the existing pavement using a broom and/or
compressed air to the satisfaction of the Engineer.
* (Guidelines by CRRI)
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Confirm that the existing pavement is dry.
Fill cracks exceeding 3 mm wide with appropriate crack sealant/bituminous
material by a method approved by the Engineer.
Level faulted cracks or joints with vertical deformation greater than 12 mm; use
a fine- grained bituminous mixture or other suitable material.
Properly repair potholes and other pavement distress to make them even with
the existing pavement surface. Repair shall be performed as directed by the
Engineer.
Allow crack filler & patching materials to cure prior to the application of tack coat.
A profile correction course shall be laid, wherever required, before placing the
paving fabric.
Step – 2- Placing a Leveling course
Apply a leveling to uneven, rutted, or extremely rough surfaces. For best results,
place a leveling course (20 to 25 mm thick), whenever possible, before placing
the paving fabric.
This will maximize performance of the paving fabric by reducing reflective
cracking. A leveling course does several important things to promote success of
the overlay including providing a smooth surface on which to place a paving
fabric and a fresh, unoxidised surface to which the paving fabric or new overlay
can bond. Placing a paving fabric directly on an old surface can cause wrinkles,
which can themselves reflect a crack upward to the surface of the overlay.
Step - 3 Tack Coat Selection & Application
Selection of proper tack coat and application rate is one
of the most important aspects in construction and
performance of certain paving fabric interlayers.
The tack coat used to impregnate the fabric and bond
the fabric to the pavement shall be paving grade
bitumen of 80/100 penetration (VG-10). Minimum air and pavement temperature shall be a t
least 10°C or more for placement of tack coat. Neither tack coat nor paving fabric
shall be placed when weather conditions, in the opinion of the Engineer, are not
suitable.
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Tack coat should be applied uniformly at the specified rate using a calibrated
distributor spray bar. Hand spraying and brush application may be used in locations
of fabric overlap. Every effort shall be made to keep the hand spraying to a
minimum.
The target width of tack coat application shall be equal to the paving fabric width
application plus 150 mm.
The tack coat shall be applied only as far in advance of paving fabric installation as
is appropriate to ensure a tacky surface at the time of paving fabric placement.
Traffic shall not be allowed on the tack coat. Any spillage or excess tack coat should
be either removed or sand sprayed over it.
Common field problems with tack coat applications include proper temperature
control, clogged or leaking spray bars or nozzles, application of too much or too
little material, and non-uniform distribution. Distribution must be uniform; do not
turn the outer nozzles perpendicular to the spray bars.
Application Rate of Tack Coat
The tack coat shall be applied, uniformly to the prepared dry pavement surface at
the rate of 1 kg/m2 of as recommended by the paving fabric manufacturer and
approved by the Engineer.
Within street intersections, on steep grades or in other zones where vehicle
speed changes, the normal application rate shall be reduced by about 20 percent
or as directed by the Engineer.
Temperature Control
The temperature of the tack coat shall be sufficiently high (140°C) to permit a
uniform spray pattern. To avoid damage to the fabric, distributor tank
temperature shall not exceed 160°C.
The paving fabric shall be installed while asphalt is still tacky.
A noncontact thermometer is useful in determining binder temperature.
Measuring Tack Rate
Tack rate should not be reduced to solve construction problems. Such reductions
can cause subsequent system failure.
Tack rate should be verified using pre-weighed, thin pans place directly in the
path of the distributor truck. The pans can be recovered after passage of the
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distributor truck and weighed to compute the tack application rate. If measured
tack rate is different from specified rate, it should be appropriately adjusted
before further use.
Insufficient tack rate is the leading cause of poor fabric interlayer performance
and failure. Insufficient tack will result in unsaturated fabric, which can lead to
overlay slippage and/or debonding and will not provide waterproofing.
Step -4: Placing the paving fabric
The paving fabric shall be placed on a dry
surface. In case, it rains after installing the
paving fabric, but before placing the overlay
over it, all excess water should be removed
and the fabric should be allowed to dry up
sufficiently before placing the overlay.
The paving fabric shall be placed with heat set side facing up, onto the tack coat
using mechanical or manual lay down equipment capable of providing a smooth
installation with a minimum amount of wrinkling and folding. Slight tension can
be applied during paving fabric installation to minimize wrinkling.
If, wet fabric is applied or if fabric is applied on damp pavement, blistering can
occur because of vaporization of moisture underneath the asphalt- impregnated
fabric.
Pavement that has recently received rainfall but has a dry surface can retain
enough moisture to cause blistering. If blisters appear, workers should eliminate
them by using a lightweight rubber-tired roller before overlaying.
The paving fabric shall be placed prior to the tack coat cooling and losing
tackiness.
Paving fabric shall not be installed in areas where the overlay bituminous layer
tapers to a thickness of less than 40 mm.
Excess paving fabric, which extends beyond the edge of existing pavement orareas of tack coat application shall be trimmed and removed. Wrinkles or folds in
excess of 25 mm shall be slit and laid flat.
Brooming and/or pneumatic rolling should be done immediately after the
placement of the paving fabric to maximize paving fabric contact with the
pavement surface.
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All areas with paving fabrics placed will be paved the same day.
No traffic except necessary construction equipment will be allowed to drive on the
paving fabric. After laying the paving fabric, some loose bituminous concrete
should be sprinkled on it in the wheel path of the paver and the tipper to ensure
that the fabric is not picked up between the wheels.
Turning of the paver and other vehicles shall be done gradually and kept to a
minimum to avoid movement and damage to the paving fabric. Abrupt starts and
stops shall also be avoided.
Additional tack coat shall be placed between the overlap to satisfy saturation
requirements of the fabric. Overlap shall be sufficient to ensure full closure of the
joint but not exceed 150 mm. Overlaps of adjacent rolls shall be staggered by a
minimum of one metre.
All overlaps shall be stitched unless specifically allowed by the Engineer not to
stitch.
The stitching procedure shall be as recommended by the manufacturer. .
The paving fabric should be pegged at suitable locations and as directed by the
Engineer, so as to avoid wrinkles and folds during the placement of the overlay.
Damaged fabric shall be removed and replaced with the same type of fabric.
Step - 5 Bituminous overlay construction
Bituminous overlay construction shall closely
follow fabric placement.
All areas in which paving fabric has been
placed will be paved the same day.
Excess bitumen which bleeds through the
paving fabric shall be removed by spreading
hot mix or sand on the paving fabric.
The hot mix should be placed between a temperature range of 130°C to 145°C so
as to give enough heat to the bitumen in the tack coat to rise up the fabric.
No reduction in the overlay thickness shall be made on account of the use of pavingfabric.
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4.3 Use of Geotextiles for Subgrade Dewatering.
Introduction to the Problem
A high groundwater table can, and often does, interfere with the stability of subgrade
soils. For instance, some clay soils can swell or shrink as their water content increases or
decreases, respectively. Also, most soils are considerably weaker when they have high
water contents or have not been drained prior to loading. This means that weather-
related or seasonal fluctuations in groundwater levels can adversely affect permanent
structures founded on undrained soils. Draining saturated soils can increase their
strength and stability. Unfortunately, soils will only drain if there is an adjacent soil layer
or zone of higher permeability into which the water can escape. The lower the
permeability of the subgrade soils, the closer together the drainage layers/zones must
be to provide effective dewatering.
Typical Solutions
The traditional approach to subgrade dewatering is to dig a trench to the depth to whichthe water table is to be lowered and filling the trench with coarse drainage stone.
Sometimes a perforated pipe is placed at the base of the trench to more efficiently
transport collected seepage to an outlet. Trenches are spaced to assure drainage of the
soil within a desired time period. Alternatively, in new construction, a coarse aggregate
drainage layer or “blanket” can be constructed beneath and before placing the subgrade
soil. Similarly, a pipe system is commonly placed within the drainage layer to transport
collected seepage. Since groundwater seeping into a drainage layer can carry subgrade
soil particles with it – a phenomenon called “piping”. To prevent piping, a layer of fine
sand is commonly used as a filter over a drainage layer or in lieu of coarse stone in a
trench.
The Geotextile Solution
Effective subgrade dewatering requires a very porous drainage media to accept seepage
and a properly graded filter to prevent piping. Geotextile materials have become
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commonplace in subsurface drainage applications. Commonly, geotextiles are being
used in lieu of select grades of sand because they are less expensive, provide more
consistent properties, and are much easier to install.
The advantages of geotextile filters can be extended to the drainage medium. Where
coarse aggregate can be costly, have variable gradations, and be costly and burdensome
to install, a geocomposite drain incorporating a 3- dimensional plastic drainage core
wrapped with a filtration geotextile overcomes all of these limitations.
INSTALLATION OF GEOTEXTILES FOR SUBGRADE DEWATERING
Trench excavation shall be performed in accordance with details of the project
plans. In all instances excavation shall be done in such a way as to prevent large
voids from occurring in the sides and bottom of the trench. The graded surface
shall be smooth and free of debris.
The geotextile shall be placed in the trench loosely with no wrinkles or folds, and
with no void spaces between the geotextile and the ground surface. Successive
sheets of geotextiles shall be overlapped a minimum of 12-in. (300 mm), with
the upstream sheet overlapping the downstream sheet. After placing the
drainage aggregate in trenches equal to or greater than 12-in. (300 mm) wide,
the geotextile shall be folded over the top of the backfill material in a manner to
produce a minimum overlap of 12-in. (300 mm). In trenches less than 12-in.
(300 mm) but greater than 4-in. (100 mm) wide, the overlap shall be equal to
the width of the trench. Where the trench is less than 4-in. (100 mm), the
geotextile overlap shall be sewn or otherwise bonded.
Should the geotextile be damaged during installation, or drainage aggregate
placement, a geotextile patch shall be placed over the damaged area extending
beyond the damaged area a distance of 12-in. (300 mm), or the specified seam
overlap, whichever is greater.
Placement of drainage aggregate should proceed immediately followingplacement of the geotextile. The geotextile should be covered with a minimum of
12-in. (300 mm) of loosely placed aggregate prior to compaction. If a perforated
collector pipe is to be installed in the trench, a bedding layer of drainage
aggregate should be placed below the pipe, with the remainder of the aggregate
placed to a minimum required construction depth. The aggregate should be
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compacted with vibratory equipment unless the trench is required for structural
support.
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5. CASE STUDIES ON USAGE OF GEOTEXTILES IN ROAD
Case Study -1: Use of Geotextiles in major district road (MDR) for
separation- Pune
Case study 2: Use of geotextiles as separator at Gadimoga
Case Study 3: Using of Geotextile in Ichalkaranji
Case Study 4: Woven Geotextiles for making paved roads at KOPT, West
Bengal
Case Study 5: Use of High strength Geotextile for Ground improvement
Case Study 6: Geotextiles for prevention of Cracks in Roads in TataPowers Co.
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5. CASE STUDIES ON USAGE OF GEOTEXTEXTILES INROADS
CASE STUDY -1: USE OF GEOTEXTILES IN MAJOR DISTRICT ROAD( MDR) FOR SEPARATION- PUNE
BRIEF SUMMARY
A 2km stretch on the problematic road MDR82 was identified.
The history revealed that this road was required to be constructed every year
owing to severe deformation and rut formation.
Soil analysis revealed that the soil is black cotton soil expanding in nature. It is
characterized by its extreme hardness and deep cracks when dry and with
tendency for heaving and swelling during the process of wetting.
Roadbeds made up of such soils when subjected to changes in moisture content
due to seasonal wetting and drying or due to any other reason undergo
volumetric changes leading to pavement distortion, cracking and general
unevenness.
Considering all above points and characteristics of soil, a scientific design of the
road cross-section was prepared and Geo-textile was fabricated. Laying of the
fabric was completed in April 2004.
The performance of the road was monitored every six months and in October
2010 (after 6 years 6 months) no abnormalities were reported.
Background of the road status along MDR82: On an average, rut depths were
observed to range from 200-300 mm. Along this particular stretch, every year new road
is constructed.
The reasons identified were,
(i) Presence of a swelling sub-grade, like black cotton soil,
(ii) Inadequate drainage,
(iii)Seasonal heavy traffic with higher axle loads,
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Status of road along MDR82 in July 2003
During the process of severe rut formations, non-uniformity in load spreading
phenomena occurs. This results in inadequate sub-grade reaction at one side (where
thinning of the aggregate layer occurs) and more than adequate sub-grade reaction at
other side (i.e. where thickening of aggregate layer occurs). This type of situation
reduces the design life of the road affect the riding quality and increase maintenance
cost. In such situations, one of the viable alternatives is to strengthen the road by
introducing a reinforcement layer in the form of geo-textile at the interface of a granular
sub-base layer and
prepared sub- grade.
Load spreading phenomena of sub-base on weak sub-grade
For the roads constructed on weak sub-grade, the inclusion of geo-synthetics, like geo-
textiles or geo-grids can lead to less deformation of the road and can reduce the
thickness of base materials needed. In many cases, this can be cost-effective, as the
savings in importing the base material and in repairs to the road can offset the cost of
reinforcement. A geo-synthetic placed at the interface between the aggregate base
course and the sub-grade functions as a separator to prevent two dissimilar materials
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(sub-grade soils and aggregates) from intermixing. Geo-textiles and geogrids perform
this function by preventing penetration of the aggregate into the sub-grade. In addition,
geo-textiles prevent intrusion of sub-grade soils into the base course aggregate.
Localized bearing failures and sub-grade intrusion only occur in very soft, wet, weak
sub-grades. Therefore, separation is important to maintain the designed thickness and
the stability and load carrying capacity of the base course. The stabilization of roads on
weak sub-grade with a geotextile material is primarily attributed to the basic functions of
separation of the base course layer from the sub-grade soil, and a reinforcement of the
composite system. Geo-synthetics are thus a great boon for ease in construction over
soft soil as well as long-term performance of roads.
Schematic cross-section of geo-textile reinforced road (All dimensions are in meters)
Soil properties
The soil sample was collected 300 mm below natural ground surface along MDR82. All
the laboratory tests were conducted as per relevant Bureau of Indian Standards. The soil
is having a specific gravity of 2.80 and liquid limit equivalent to 69 % and plastic limit
equivalent to 33 %. The soil is having 62 % particles finer than 2 micron size, greater
than 2 micron but less than 75 micron size equivalent to 20.2 %, greater than 75 micron
but less than 4.76 mm size equivalent to 11.8 %, and > 4.76 mm equivalent to 5.9 %.
The soil can be classified as per IS: 1498, as CH type. CH indicates inorganic clays with
high plasticity.
In order to assess an un-drained cohesion of the soil, unconsolidated un-drained (UU)
tri-axial compression tests were conducted on saturated samples. Samples were molded
at maximum dry unit weight and optimum moisture content. The tests were conducted
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at three cell pressures namely: 0.5, 1.0 and 1.5 kg/cm2 respectively. The results of
these indicate that the soil has got an un-drained cohesion equivalent to 52.5 kN/m2.
Table 1 presents the summary of soil properties. An average free swell of the soil
sample collected is obtained as 93 %, which indicates a high degree of expansion. CBR
value under un-soaked conditions is 7.8 % and with four days soaking in water CBR
values are obtained as 3 % and 1.8 % with 7 days soaking respectively. The black
cotton soil with pure fines in under soaked conditions, CBR value generally ranges from
1 - 1.5%.
The sub-grade soil is of a black cotton soil and expanding in nature. Potentially
expansive soils, such as, black cotton soils are montmorillonite clays and are
characterized by their extreme hardness and deep cracks when dry and with tendency
for heaving during the process of wetting. Roadbeds made up of such soils when
subjected to changes in moisture content due to seasonal wetting and drying or due to
any other reason undergo volumetric changes leading to pavement distortion, cracking
and general unevenness. A proper design incorporating the following measures may
considerably minimize the problems associated with expansive soils. As per IRC:37-
2001, one of the alternatives is to stabilize the soil using quick lime extending over the
road formation width along with measures for efficient drainage of the pavement
section.
Design details of geo-textile reinforced roadThe design of the geo-textile reinforced road was carried out as per the procedure
outlined by Giroud and Noiray (1981). By taking the properties mentioned in Tables 1
and 2 the pavement block sections with and without geo-textile layer were arrived.
Keeping in view of the expansive nature of the sub-grade, the sub-grade is pre-treated
with lime and saturated with water trickling. The design particulars include the following:
un-reinforced aggregate thickness with traffic h0 is equivalent to 0.72 m and whereas
reinforced aggregate thickness with traffic hR works out to be 0.51 m. The reduction of
aggregate thickness, Δh, resulting from the use of a geo-textile, is 0.21 m. This resultsin 29 % percentage savings in the aggregate requirement.
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The construction methodology involves trimming of the existing road surface and
widening to obtain the road formation width for the entire 2 km stretch along MDR82.
This is followed by treating the sub-grade in two stages: (i) by forming lime + black
cotton soil mix trenches on both sides and (ii) spreading of lime on top of the prepared
sub-grade and tricking with water
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Status of un-reinforced road along MDR82 as on September 3, 2004
The geo-textile is overlaid on a compacted soft murrum base and pegged along the
edges to keep it in position. After laying the geo-textile, a thin layer of soft murrum was
laid to cushion the geo-textile fabric. This is adopted to protect the geo-textile from any
damages during laying, installation and post-construction stages. The laying of the fabric
was completed in April 2004 and is currently in the monitoring stage. The surface of the
road was built on the sub-grade of almost identical conditions but without any ground
improvement. The initiation of a rutting can be noted in Fig. Contrary to this, the
reinforced stretch was observed to behave well with reduced deformations and rutting.
This shows the significant influence of a geo-textile layer along with a lime treatment in
enhancing the performance of the road stretch along MDR82.
View of the road during laying of geotextile
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Condition of the Road after 7 years in 2011 (Without Geotextile)
Condition of the Road after 7 years in 2011 (With Geotextile)
Status of the geo-textile reinforced road on September 3, 2004
CONCLUSIONS
In this paper, the design details, sub-grade treatment and construction methodology of
a demonstration project involving the use of Polypropylene woven geo-textile as a
separator cum reinforcement for a road were presented. A 2 km long stretch of road
along MDR 82 in the Daund Region of Pune district was selected for this project. The
project was undertaken to evaluate and compare the performance of a geo-textile
reinforced stretch of the road with adjoining stretches of road with conventional design
under identical conditions. Keeping in view of the site conditions, a 5 m wide
Polypropylene slit tape based woven fabric was custom designed and assessed for its
properties. Monitoring of this stretch is currently under progress. Preliminary
observations show that, in the geo-textile reinforced section of the road, there are no
signs of visible distress even after about five months; where as earlier experience
showed that road constructed as per standard conventional practice deteriorated within
6 months. This shows the significant influence of a geotextile layer along with a lime
treatment in enhancing the performance of the road stretch along MDR82.
Courtesy: Reliance Industries Ltd
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CASE STUDY 2: USE OF GEOTEXTILES AS SEPARATOR AT GADIMOGA
Client: M/S Reliance industries Ltd
Consultant: M/S L&T RambollSite Location: Village Gadimoga located about 25 Km from Kakinada, APCompletion Date: April 2007
Products used: Woven Slit Film Geotextiles
Reliance industries is developing onshore terminal for KG D-6 field development near thevillage Gadimoga located in state of Andhra Pradesh.
As a part of the development for KG D6, RIL has constructed internal haul roads on theexisting ground conditions having soil with very low CBR value
RIL and consultant L&T Ramboll had proposed to use Tape Woven Geotextiles for theapplication of reinforcement and separator between Granular sub-base and sub-grade.The total quantity used in the project was 212660 m2.
A schematic sketch of the roads using the woven geotextiles is shown below:
Courtesy: Techfab (India) Industries Ltd
Design details for the roads
Cross-section of the road with Geotextiles
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CASE STUDY 3: USING OF GEOTEXTILE IN ICHALKARANJI
Contractor: Ichalkaranji Municipality
This was one of the first projects where geotextiles were used in India. The Geotextiles
were used in 1990, 21 years from now. The problem was deterioration of roadfrequently.
Laying of Geotextiles in 1990
Road without geotextiles
Road with geotextiles
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Woven geotextiles were used and the problem was reduced to a great extent.
To check the efficacy of geotextiles after several years, Geotextiles were excavated after
10 years. The test results showed that strength of geotextiles have not changed
significantly in the machine direction, proving that Geotextile can be a long time solution
to the problems of the roads.
Courtesy: Kusumgar Corporates pvt ltd
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CASE STUDY 4: WOVEN GEOTEXTILES FOR MAKING PAVED ROADSAT KOPT, WEST BENGAL
BENEFITS: Paved roads are the ones which carry heavy
vehicular movement. At dockyard a typical load would be
movement of heavy containers. Also the bottom most is a
weak base of sub soil. Woven Geotextile improvise the
subgrade and strengthen the same. Base reinforcement and
bearing capacity is improved. Reduction in thickness of the
granular layer can also be done. Use of Woven Geotextiles prevents aggregate
penetration and mud pumping.
INSTALLATION: Woven Geotextile was laid on the weak sub
soil, after clearing and leveling the same. Laying of rolls was
done manually overlapping each other, which was then stitched
with nylon threads. Post this more soil is laid and layered with
a road roller. Water is sprinkled; soil settles down and then
starts the laying of paver tiles. This is a process driven simple
installation.
Sr. No. Parameter Results
1 Grab Tensile in LBS (ASTM 250- Warp250 -Weft
2 Elongation in % (ASTM D:4632- 15- WARP
15- WEFT
3 Bursting Strength in P.Si (ASTM
D:3786-87)
450
90- WARP4
Trapezoidal Tear Strength in LBS
(ASTM D:4533-91) 90- WEFT
5Index Puncture Resistance in LBS
(ASTM D:4833-91)100
6 AOS in mm (ASTM D: 4751: 95) * 0.425
7Water Permeability in Gal/SF/min(ASTM D: 4491) *
4
8 UV Resistance in % per 500Hrs 70
*: Values are Maximum Average Roll Values. These are typical values at the time of
production. Handling and transportation may change these values.
Courtesy: Shri Ambica Polymer Private ltd
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CASE STUDY 5: USE OF HIGH STRENGTH GEOTEXTILE FOR GROUND IMPROVEMENT
Contractor: Simplex InfrastructureApplication of geotextiles as a separator cum drainage medium:
• A lagoon 210 m x 130 m was made by construction of earthen bunds of height 3.6 m
on marshy land having very soft marine clay deposit of 4.0 to 8.0 m thickness.
• Sand drains of 250 mm were used to improve ground improvement.
• Geotextiles have been used to prevent the ingress of murrum bund into sand blanket.
Year of laying: 1997
Feedback: Geotextiles has been used as separator as ground improvement work at the lagoon site,
since then it is still it is serving its function.Courtesy: Kusumgar Corporates Pvt. Ltd
Layout pattern of sand drain
Fabric Orientation in Bund
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CASE STUDY 6: GEOTEXTILES FOR PREVENTION OF CRACKS INROADS IN TATA POWERS CO.
On permanent road structures we often see cracks generated and getting converted into
Ruts. The main causes for development of the cracks are; these road structures aresubjected to varying loads from the vehicles running over them as well as extreme
weather conditions have severe effects on the stability of the roads.
Conventional Method For Repair
Generally these roads are resurfaced with a fresh
coat of Bitumen. But the cracks start appearing again
on the resurfaced roads. This is due to reflection of
the cracks already formed on the earlier layer of
bitumen and this phenomenon is known as reflective
surface cracking.
Most Preferred Solution Globally
The most preferred method to delay the crack
formation on to new surface coat is to reinforce this
layer by introducing a Polypropylene Non Woven
Geotextile layer just beneath it (DBM). This layer does
two main functions; waterproofing or subsurface
drainage and reinforcement. This Geotextile layer acts
as a fluid barrier when impregnated with Bitumen from one side; also it drains the
surface moisture in lateral direction protecting the underlying layers. Secondly it acts as
a stress relieving layer and prevents the stresses developed in underlying layer to reflect
in new layer. Thus the useful life of the new layer is extended exponentially.
Why PP Non-Woven Geotextiles
The non-woven paving fabric is manufactured from high quality polypropylene fibres,
with heat treatment on one side to form a strong, flexible and dimensionally stable
fabric structure with optimum bitumen retention capacity. Polypropylene is one of the
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most durable polymers with excellent resistance to both acidic and alkaline
environments. The affinity of Polypropylene for liquid asphalt ensures an excellent bond
between the fabric and the asphalt tack coat. High melting point of PP results in
withstanding high temperatures of bituminous mixes.
Introduction: A project was undertaken at Tata Power in 2007. The problem was heavy
rutting and appearance of cracked surface frequently.
Steps of Laying:
Basic preparations like cleaning with high pressure air,
filling of cracks and pot holes at the site were carried out.
A tack coat of bitumen was then applied the cleaned
surface of the road with the help of sprayers.
The fabric was then carefully laid on the tack coat with
the heat sealed side of the fabric facing the tack coat. It
was ensured that there are no wrinkles and folds on the
fabric to avoid formation of air pockets. Brooming of the
fabric was done to ensure complete removal of wrinkles.
After laying pegging was done to avoid wrinkle formation
during later operations.
A layer of DBM (dense bituminous macadam) was then
placed over the fabric. It was then compacted using road
rollers. A layer of BC (bituminous concrete) was then
placed over DBM and compacted. Traffic movement was
then allowed on the road.
Courtesy: Kusumgar Corporates Pvt ltd
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6. JUTE TEXTILE
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6. JUTE GEOTEXTILE
Jute Geotextile is a natural geosynthetics made out of jute-fibers. Jute is a low cost,
renewable, biodegradable and eco-friendly natural product. Jute was tried long back as
field experiment s before the concept of
geosynthetics was thought of, Jute was applied
in a road at Dundee in Scotland in 1920,on
Strand Road at Kolkata, India in 1934 by
Bengal PWD and in a road in Mynamar during
World War II was reportedly successful. Use of
Jute geotextile for improvement of the
performance of various geotechnical structures
had been extensively studied, jute geotextile impart strength to the soil by performing
three basic functions like separation, filtration and drainage. An in depth research
carried out in this field has shown that Jute Geo-textile if properly treated with
appropriate chemicals can successfully protect the roads and embankments against
erosions and can also guarantee a desired durability.
Jute geotextile is having some of the advantages over synthetic geotextiles such as it is
much cheaper than synthetic fibre, It is easy to blend with other natural material and
synthetic fibres, it is environmental friendly, design biodegradable, hydrophobic, anionic
and easily available material. Initially it has got the high strength and non-hazardous
properties. It is also a renewable source of energy as natural biomass.
Applications of Jute Geotextile:
• Protection of all kinds of earth-slopes
• Stabilization of embankments of roads & railways
• Control of erosion of banks of rivers & waterways
• Strengthening of roads, including haul roads
• Control of settlement in roads & railway tracks
• Stabilization of all kinds of spoil heaps, PFA
• As anti-pollutant cover over solid wastes
• For quick development of greeneries, lawns
• Consolidation of soft soil
• Construction of concealed drains in hill roads
• As facilitator of vegetation-growth in arid & semi-arid zones
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Jute Geotextiles in Roads
Jute Geotextiles as Separator to Improve Pavement Performance
The performance of pavements constructed on soft
soils can be improved using jute geotextiles. Jute
fabric when used as separator prevents the
penetration of subgrade material into voids of
granular base course. The permeability
characteristic of the fabric also aids in faster
dissipation of pore pressures and ensures better drainage which results in better long
term performance of the pavement. Provision of fabric enables subgrade develops its full
bearing capacity and thus controls rutting.
Jute Geotextile for Drainage and Filtration
To arrest the sinking of road pavement, a
systematic network of roadside trench drains and
cross trench drains are constructed using non-
woven jute geotextiles. The trench drains are made
of rubbles encapsulated in non-woven jute
geotextiles to stop the finer particle entering into
the voids of encapsulated rubbles, thereby
preventing clogging the trench drains.
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7. CASE STUDIES OF JUTE GEOTEXTILES IN ROADS
Case Study 1: Construction of Highway Embankment on Soft Marine soil
at Kakinada Port, India
Case study 2: Widening of Munshirhat- Rajpur Road, India
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7. CASE STUDIES ON USAGE OF JUTE GEOTEXTILES INROADS
Case study 1: Construction of Highway Embankment on SoftMarine soil at Kakinada Port, India
1. Leveling in Progress
2. Laying of Jute Geotextile
3. Condition of road after seven years of
construction
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Case study 2: Widening of Munshirhat- Rajpur Road, India
1. Jute Geotextile is laid on the
subgrade
2. Consolidation of brick metal laidover JGT on widened portion.
3. Finished road after widening
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8. GEOTEXTILES IN EROSION CONTROL
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8. GEOTEXTILES IN EROSION CONTROL
Geotextiles are the most widely used Geosynthetics
products and find application in many infrastructure
projects. For river bank protection, the major function
of geotextiles is filtration.
WHAT IS GEOTEXTILE FILTER?
A Geotextile placed in contact with soil, allows water seeping from the soil to pass
through while preventing any movement of soil particles (with the exception of a very
small amount of the fine particles located near the filter).
CONVENTIONAL SYSTEMS VIS-À-VIS MODERN
GEOTEXTILES PROTECTIONConventional methods to tackle the problem of Soil
Erosion includes construction of flexible structures
such as rip-rap or heavy armor stones, concrete
blocks, articulated concrete mattresses to break up
the water forces. To prevent washing away of the
underlying soil, layers of granular materials (graded filters) are placed between
underlying soil and rip-rap. A typical graded filter consists of successive layers of
sand, gravel and stones, the particle size of which are calculated. At times, minimum
four layers of different materials may be required in conventional methods
Shortcomings
When rip-rap revetment is used to dissipate the hydraulic forces, turbulence occur within
the interstices of the erosion control structure resulting in erosion of the base soil
through the pores in the facing.
Modern Geotextile Filters
Geotextiles are frequently used as replacement for
grades, the advantages associated are
Comparable performance,
Improved economy, Consistent properties and ease of placement. Reduction in number of granular layers
Lower overall cost & faster construction
Conventional
Geotextile Protection
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9. CASE STUDIES: GEOTEXTILES IN EROSION CONTROL
Case Study 1 - Geotextiles for Swan River Embankment Protection, Una, HP
Case study 2 - Geotextiles and Geobags For Churni River EmbankmentProtection, West Bengal
Case Study 3 - Geotextile Reinforced Embankment for Height Raising of JarositePond at Zinc Smelter, Debary, Udaipur
Case Study 4: Erosion control Measures for the Bhagirathi River
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9. CASE STUDIES - GEOTEXTILES IN EROSION CONTROL
Case Study 1 - Geotextiles for Swan River EmbankmentProtection, Una, HP
Swan River Project
51km River Embankment Project to prevent flood
Year of Laying- 2009
Two phases, 1st phase of 17km is complete,
Imported Geotextiles used in 1st phase,
2nd phase Repol PP based Needle Punched Non
Woven Geotextiles specified,
Repol PP based Needle Punched Geotextile
confirms the specifications laid down by
authorities.
Domestic product certified by IIT Delhi
131000 Sq. Mtr. Geotextiles used.
Process Of Construction Of Embankment
Base embankment is compacted
A layer of 310GSM, 2.5mm Thick PP Needle
Punched Non Woven Geotextile is laid
Gabions filled with Boulders are placed over the Geotextile
Function of PP Needle Punched Non Woven Geotextile Geotextile functions as a filter,
Prevents soil from embankment from being washed away,
Reduced the damage to the base embankment considerably
Extends life of embankment
Advantages of geotextile system v/s. Conventional riprap
Reduction in Granular layers
Considerable saving of construction time
Longer life of the embankment even after repeated floods.
Advantages of Polypropylene Non Wovens
Polypropylene is one of the most durable polymers
Excellent resistance to both acidic and alkaline environments
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Failure of Conventional Grade Filters
Construction of Embankment with PP Needle Punched Non Woven Geotextile
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Laying of Geotextiles
Laying of Gabions over Geotextile (Single Rip-rap layer)
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Laying of Gabions over Geotextile
Final Embankment with rip-rap and geotextiles
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SPECIFICATIONS OF THE PP NON WOVEN GEOTEXTILE
The general specifications of the Polypropylene Non Woven Geotextile requiredin project were as follows.
Sr Test Standard Unit Specification
1 Weight (GSM) ASTM D 5261 GSM > 275
2 Thickness ASTM D 5199 mm > 2.5
3 Pore Size ASTM D 4751 mm 0.15 to 0.20
4 Water Permeability BS 6906/3 Ltr/Sqm/s 150 to 160
5 CBR Puncture Strength ASTM D 4833 N > 3850
6 Wide Width Tensile Strength ASTM D 4595 kN/m > 17.5
7 Grab Tensile Strength ASTM D 4632 N > 1100
8 Elongation at break ASTM D 4632 % < 50
9 Cone Drop BS 6906/6 mm < 15
10 Trapezoidal Tear Resistance ASTM D 4533 N < 450
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Geotextiles Supplier: Techfab (India) Industries LtdCompiled by: Reliance Industries Ltd
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PROCESS OF CONSTRUCTION OF EMBANKMENT
Project started in 2009 and was completed in Jan 2010.
Base embankment was compacted
A trench 2’ x 4 ‘ was made at the top and bottom of the embankment
A thick layer of Geotextile as Filter Fabric was laid.
To secure the geotextile, the trench was filled with boulders placed in a metal gabion.
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The embankment was protected with two layers of bricks
(as they were readily available)
Two layers of 6500 sand filled, PP geobags were placed at edge of the river to take
care of the soil erosion.
Function of Geotextiles and PP Non Woven Bags
Geotextiles function as a filter.
Geotextiles prevent soil from embankment from being washed away,
PP Geo-bags provide reinforcement to the edge of the embankment
Advantages of Geotextile system v/s. Conventional riprap
Reduction in Granular layers
Considerable saving of construction time
Longer life of the embankment even after repeated floods.
Compiled by: Reliance Industries Ltd.
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Case Study 3 - Geotextile Reinforced Embankment for Height
Raising of Jarosite Pond at Zinc Smelter, Debary, Udaipur
Name of the Client : Hindustan Zinc Limited
Year : 2010Project Details :
The client intended to raise the height of the existing embankment to increase the
capacity of the jarosite pond. The height of the embankment varied from 6.0 m and
14.0m.
To minimize the foot print area of the embankment and the quantity of the embankment
fill, reinforced embankment slope was proposed by using Polyester Woven Geotextile as
reinforcement.
Use of woven geotextile to reinforce the steep embankment slopes was found to be a
technically viable and economical option.
Courtesy: Garware Wall Ropes Ltd.
During Construction of Reinforced
Embankment Slope
After Construction of Reinforced
Embankment Slope
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Case Study 4: Erosion control Measures For the Bhagirathi river
Material: 240 GSM based on PPMF (polypropylene multifilament)
Department: Nadia Irrigation Division, West Bengal
Contractor: Jashjit Mukherjee
Courtesy: Kusumgar Corporates Pvt Ltd.
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10. POLYMER GABIONS IN EROSION CONTROL
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10. POLYMER GABIONS IN EROSION CONTROL
1 Introduction
Coastal areas are prone to erosion due to continuous
impact of waves and tides. The waves slowly erode the
natural coast and over a period can cause danger to the
structures near shore. One of the most cost effective
techniques for the coastal area protection is the usage of
Rope or Polymer Gabions.
2 What is Rope or Polymer Gabions?
Polymer Gabions are 3-Dimensional flexible box like
structures fabricated from polymer ropes and usually filled
with stone and used for structural purposes such as retaining
walls, revetments, slope protection, and similar applications.
3 Modern Rope Gabion Vis-À-Vis Conventional Steel Gabion
Polymer Gabion made from PP has following advantages over steel Gabions:
Excellent flexibility: The inherent flexibility of the rope and the continuous
integral construction imparts excellent flexibility to the gabion, allowing it to
adapt itself to uneven surface profiles and to accommodate significant amountsof differential settlements and movements while retaining structural integrity and
continuity.
High Resistance to corrosion: PP is highly resistant to the chemical and
biological environments normally encountered in most applications. Hence PP
gabions do not corrode even in aggressive marine environments.
High tensile strength: The PP rope used to produce gabions, has very high
tensile strength
Ease of Installation: Supplied in ready to fill collapsed form.
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11. CASE STUDY: POLYMER GABION FOR EROSION CONTROL
Case Study 1: Polymer Gabions for Tithal Beach- Swami Narayan Temple,
Daman
Case Study 2: Polymer Gabions for erosion control- Mahisagar River-
Vadodara
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11. Case Study on polymer gabions for erosion control
Case Study 1: Polymer Gabions for Tithal Beach- Swami NarayanTemple, Daman
Tithal beach (north of Daman) is known for its
prominent Swaminarayan and Saibaba Temple.
Over the years the beach started getting eroded
due to waves and it was estimated that within 5-
7 years the beach up to the temple would