Handbook of Geotextiles

8/17/2019 Handbook of Geotextiles

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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


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.


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


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.


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.


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.


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 subgrade.

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

Documents

Handbook of Geotextiles