role of geotext

8/10/2019 Role of Geotext

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INTRODUCTION

Geotextiles are permeable fabrics which, when used in association with soil, have the

ability to separate, filter, reinforce, protect, or drain. Typically made from polypropyleneor polyester, geotextile fabrics come in three basic forms: woven (looks like mail bag

sacking), needle punched (looks like felt), or heat bonded (looks like ironed felt).

As the use of geotextile fabrics has expanded, geotextile composites have been introduced

and products such as geogrids and meshes have been developed. verall, these materials

are referred to as geosyntheticsand each configuration!geonets, geogrids and others!

can yield certain benefits in geotechnical and environmental engineeringdesign. These

products have a wide range of applications and are currently used to advantage in many

civil engineeringapplications including roads, airfields, railroads, embankments, retaining

structures, reservoirs, canals, dams, bank protection and coastal engineering. "sually

geotextiles will be placed at the tension surface as it will strengthen the soil.

#eotextile can be used as an innovative way to improve soil strength, instead of the

conventional manner using soil nailing. $t is believed that the cost to have it done is much

cheaper. $n addition, steep slopes can then be planted with beautiful vegetation to enhance

the aesthetic value.

To use geotextiles to reinforce a steep slope, two components have to be calculated:

%. the tension re&uired for e&uilibrium

'. the appropriate layout of the geotextile reinforcement

oth woven and nonwoven geotextiles perform

well when draining stable, coarsegrained soils.

*onwovens are generally used when the retention of

fine soil particles is critical to the performance of the

drainage system. #eotextile strength properties are

selected to ensure that the geotextile survives

construction and remains intact to perform as a filter.

Geosynthetics

Geosyntheticsis the term used to describe a range of generally syntheticproducts used to

solve geotechnical problems. The term is generally regarded to encompass four main

products: geotextiles,geonets+geogrids,geomembranesand geocomposites. The synthetic
http://en.wikipedia.org/wiki/Fabrichttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Geosyntheticshttp://en.wikipedia.org/wiki/Geotechnical_engineeringhttp://en.wikipedia.org/wiki/Environmental_engineeringhttp://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Soil_nailinghttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Geotextilehttp://en.wikipedia.org/wiki/Geotextilehttp://en.wikipedia.org/wiki/Geomembraneshttp://en.wikipedia.org/wiki/Geomembraneshttp://en.wikipedia.org/wiki/Geomembraneshttp://en.wikipedia.org/wiki/Fabrichttp://en.wikipedia.org/wiki/Soilhttp://en.wikipedia.org/wiki/Geosyntheticshttp://en.wikipedia.org/wiki/Geotechnical_engineeringhttp://en.wikipedia.org/wiki/Environmental_engineeringhttp://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Soil_nailinghttp://en.wikipedia.org/wiki/Chemical_synthesishttp://en.wikipedia.org/wiki/Geotextilehttp://en.wikipedia.org/wiki/Geomembranes


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nature of the products make them suitable for use in the ground where high levels of

durability are re&uired. #eosynthetics are available in a wide range of forms and materials,

each to suit a slightly different end use. These products have a wide range of applications

and are currently used in many civilandgeotechnical engineeringapplications including

roads,airfields, railroads, embankments,retaining structures, reservoirs,canals,dams,bank protectionand coastal engineering.

History

#eosynthetics of different sorts have been used for thousands of years. They were used in

roadway construction in the days of the haraohsto stabili-e roadways and their edges %/.

These early geotextiles were made ofnatural fibres, fabricsor vegetationmixed with soil

to improve road &uality, particularly when roads were built on unstable soil. Although

modern geosynthetics bear little resemblance to those used in Ancient 0gypt, the general

principles remain the same. The development of geosynthetics has been slow, mainly due

to the limitations of the materials used. 1ith the recent development ofpolymers, themodern development of geosynthetics has moved along swiftly. Their relatively recent

development and acceptance byindustryis highlighted by the fact that the $nternational

#eosynthetics 2ociety($#2) was founded in arisin %345.'/.

Types

6ollage of geosynthetic products

Geotextiles

#eotextiles are usually produced as eitherwovenornonwoventextiles. 1oven

geotextiles are produced by the interlacing of yarnsto leave a finished material that has adiscernible warp and weft5/. *onwoven geotextiles are produced by various methods
http://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Geotechnical_engineeringhttp://en.wikipedia.org/wiki/Geotechnical_engineeringhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Airfieldhttp://en.wikipedia.org/wiki/Airfieldhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Embankmenthttp://en.wikipedia.org/w/index.php?title=Retaining_structure&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Retaining_structure&action=edit&redlink=1http://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Canalhttp://en.wikipedia.org/wiki/Canalhttp://en.wikipedia.org/wiki/Damhttp://en.wikipedia.org/w/index.php?title=Bank_protection&action=edit&redlink=1http://en.wikipedia.org/wiki/Coastal_engineeringhttp://en.wikipedia.org/wiki/Yearhttp://en.wikipedia.org/wiki/History_of_Egypthttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Natural_fibrehttp://en.wikipedia.org/wiki/Natural_fibrehttp://en.wikipedia.org/wiki/Fabrichttp://en.wikipedia.org/wiki/Vegetationhttp://en.wikipedia.org/wiki/Ancient_Egypthttp://en.wikipedia.org/wiki/Polymershttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/w/index.php?title=International_Geosynthetics_Society&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=International_Geosynthetics_Society&action=edit&redlink=1http://en.wikipedia.org/wiki/Parishttp://en.wikipedia.org/wiki/Parishttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Geosynthetic#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Wovenhttp://en.wikipedia.org/wiki/Wovenhttp://en.wikipedia.org/wiki/Non-wovenhttp://en.wikipedia.org/wiki/Non-wovenhttp://en.wikipedia.org/wiki/Yarnhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-2%23cite_note-2http://en.wikipedia.org/wiki/Image:Geocollage.JPGhttp://en.wikipedia.org/wiki/Civil_engineeringhttp://en.wikipedia.org/wiki/Geotechnical_engineeringhttp://en.wikipedia.org/wiki/Roadhttp://en.wikipedia.org/wiki/Airfieldhttp://en.wikipedia.org/wiki/Railroadhttp://en.wikipedia.org/wiki/Embankmenthttp://en.wikipedia.org/w/index.php?title=Retaining_structure&action=edit&redlink=1http://en.wikipedia.org/wiki/Reservoirhttp://en.wikipedia.org/wiki/Canalhttp://en.wikipedia.org/wiki/Damhttp://en.wikipedia.org/w/index.php?title=Bank_protection&action=edit&redlink=1http://en.wikipedia.org/wiki/Coastal_engineeringhttp://en.wikipedia.org/wiki/Yearhttp://en.wikipedia.org/wiki/History_of_Egypthttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-0%23cite_note-0http://en.wikipedia.org/wiki/Natural_fibrehttp://en.wikipedia.org/wiki/Fabrichttp://en.wikipedia.org/wiki/Vegetationhttp://en.wikipedia.org/wiki/Ancient_Egypthttp://en.wikipedia.org/wiki/Polymershttp://en.wikipedia.org/wiki/Industryhttp://en.wikipedia.org/w/index.php?title=International_Geosynthetics_Society&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=International_Geosynthetics_Society&action=edit&redlink=1http://en.wikipedia.org/wiki/Parishttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-1%23cite_note-1http://en.wikipedia.org/wiki/Wovenhttp://en.wikipedia.org/wiki/Non-wovenhttp://en.wikipedia.org/wiki/Yarnhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-2%23cite_note-2


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other than weaving, mainly heat bonded, needle punched and chemically bonded. 1oven

and nonwoven geotextiles are manufactured from mainlypolymericyarns and fibres,

consisting primarily ofpolypropylene,polyester,polyethyleneandpolyamide.There are a

small group of #eotextiles that are still produced from fibrous materials, used mainly in

erosion control. Their degradable characteristics are beneficial in some applications.

Geogrids and geonets

These are discernibly stiffer than geotextiles and have relatively large voids within the

material. 7ethods of production vary but include extrusion,bondingor interlacing.They

can be produced from nearly allpolymericmaterials.

#eogrids are meshes typically made of a regular pattern of tensile elements usually made

of a fairly rigid type of plastic. These are used to strengthen fill materials in geotechnical

applications. They provide increased shear strengthbetween soil strata interfaces. Their

tensile strength can prevent or decrease the degree of differential settlement in someapplications such as beneath structures or roads by transmitting the load over a broader

area of soil, thereby diminishing the vertical stress ! and subse&uent compression ! in

the soil.

Geomembranes

0ssentially impermeable sheets produced frompolymericmaterials. #eomembranes are

manufactured several ways, excluding woven methods as they would leave unacceptably

large voids in the material. #eomembranes can also be manufactured using fibreglass and

bitumen.

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#eomembranes are used widely as cutoffs and liners. "ntil recent years, geomembranes

were used mostly ascanalandpond liners. ne of the largest current applications is the

containment of ha-ardousand municipal wastesand their leachates. $n many of these

applications geomembranes are employed with geotextile or mesh underliners which

reinforce or protect the more flexible geomembrane whilst acting as an escape route for

gasesand leachates generated in some wastes.

#eomembranes are made of various materials including low density polyethylene(90),

high density polyethylene(;0),polyvinyl chloride(


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geonet sandwiched between two nonwoven geotextile layers can be used to provide a

drainagelayer with hightransmissivity.

Applications

Table showing the general suitability of geosynthetic products to certain applications

6ollection of illustrations showing the basic functions of geosynthetics

Among other uses, geosynthetics can be used for separation, filtration,reinforcement,

drainage, protection and moisture barriers>/. ifferent geosynthetics are suited for various

applications and the diagram to the right illustrates their suitability.

Filtrationcan significantly enhance the performance of a geotechnical structure, and

geosynthetics can be used to produce an effective filtration system ?/. The @ob of a filter is

to allowwaterto pass through the plane of the filter, whilst retaining particles of the

filtered soil. =iltration can improve the performance of a geotechnical structure by

controlling the erosion of the structure and reducing the amount of fines that are washed

out of the soil matrix. 1hen fines get washed out of a soil it can reduce the cohesion of the

matrix and thus the strength of the soil, referred to as piping. 7itigating these two

problems also improves the durability of a structure. #eosynthetic filters can improve the

reliability and performance of traditional graded soil filters and re&uire less work to

construct. #eotextiles are well suited to this application.

Drainageis re&uired in nearly all geotechnical structures. 1hether used to remove surface

water from a sports field or to reduce lateralpressureon a retaining wall, the need for

effective drainage cannot be underestimated. rains of various designs have been used in

the past, most based on the use of a high permeability layer built into the ground using

aggregates, single layers of geosynthetics can produce the same results. rains can be

distinguished from filters as such water travels across the plane of filters and travels with

the plane of drains. #eotextiles and geocomposites are well suited to this application.

rotection!"arrier : in some geotechnical applications it is necessary to separate or

protect one section of the works from another. This could be for a multitude of reasons,including stopping leachate seepage, protecting a structure from moisture and protecting a

geotechnical structure from erosion. #eotextiles and geomembranes are suited to this

application.

#eparation: the geosynthetic acts to separate two layers of soil that have different particle

si-e distributions. =or example, geotextiles are used to prevent road base materials from

penetrating into soft underlying soils, thus maintaining design thickness and roadway

integrity. 2eparators also help prevent finegrained subgrade soils from being pumped into

permeable granular road basesB/. #eotextiles and geomembranes are most suited to this

application.
http://en.wikipedia.org/wiki/Drainagehttp://en.wikipedia.org/wiki/Transmissivityhttp://en.wikipedia.org/wiki/Transmissivityhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Reinforcementhttp://en.wikipedia.org/wiki/Reinforcementhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-4%23cite_note-4http://en.wikipedia.org/wiki/Geosynthetic#cite_note-5%23cite_note-5http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Retaining_wallhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-6%23cite_note-6http://en.wikipedia.org/wiki/Drainagehttp://en.wikipedia.org/wiki/Transmissivityhttp://en.wikipedia.org/wiki/Filtrationhttp://en.wikipedia.org/wiki/Reinforcementhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-4%23cite_note-4http://en.wikipedia.org/wiki/Geosynthetic#cite_note-5%23cite_note-5http://en.wikipedia.org/wiki/Waterhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/Retaining_wallhttp://en.wikipedia.org/wiki/Geosynthetic#cite_note-6%23cite_note-6


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Rein$orcement: geosynthethics can be used to reinforce a soil mass, increasing the

effective angle of shear and increasing the stability of an earth structure. $n the

reinforcement function, the geosynthetic is sub@ected to a sustained tensile force. 2oil and

rock materials are noted for their ability to withstand compressive forcesand their relative

low capacity for sustained tensile forces. $n much the same way that tensile forces aretaken up bysteelin a reinforced concretebeam, the geosynthetic supports tensile forces

that cannot be carried by the soil in a soil+geosynthetic system. #eogrid+geonets and

geotextiles are best suited to this function.

Geo textiles erosion Control%

#eotextiles have replaced graded granular filters used beneath riprap or other

armor materials in revetments. Applications include drainage channels, shorelines, and

bridge and pier scour protection systems. 1ithout a geotextile filter, wave action andwater movement erode subgrade soils from beneath the riprap or armor. egradation of

the subgrade negates the benefit of the riprap or armor,resulting in extensive repair and

replacement.

The selection of geotextiles for permanent erosion

control is similar to subsurface drainage. ;owever,

permanent erosion control applications usually re&uire

higher geotextile strength properties. The geotextile

must survive placement of possibly very large, angular

riprap, plus be able to endure severe wave action.

Geo textiles &aste Containment%

1aste containment and environmental cleanup pro@ects demand geotextiles with

uncompromising physical properties and consistent product &uality. $n environmental

applications, geotextiles must retain these critical properties while exposed to harsh

chemical environments.

1aste containment fabrics serves in a variety of environmental applications, including

filtration of fluid and gas collection systems, protection of geomembrane liners, wastedaily covers and reinforcement. geotextiles are specified for municipal waste and

ha-ardous waste landfills, heap leach pads, sewage treatment lagoons, as well as waste

containment ponds and other surface impoundments.

7aintaining track bed geometry is critical for efficient railroad operation. 2ubgrade

pumping into the overlying ballast can create an uneven track bed, resulting in delayed

arrivals and even derailments.
http://en.wikipedia.org/wiki/Structurehttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Reinforced_concretehttp://en.wikipedia.org/wiki/Structurehttp://en.wikipedia.org/wiki/Physical_compressionhttp://en.wikipedia.org/wiki/Tension_(mechanics)http://en.wikipedia.org/wiki/Steelhttp://en.wikipedia.org/wiki/Reinforced_concrete


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Geo textiles railroad #tabili'ation%

#eotextiles perform multiple functions in railroad applications. *onwoven fabrics are

used to stabili-e both new and rehabilitated tracks. They prevent contamination of new

ballast with underlying finegrained soils and provide a

mechanism for lateral water drainage. "sing nonwoven

geotextiles beneath track beds ensures that the ballast can

sustain the loads for which it was designed. These

geotextiles are used in all track applications, including

switches, turnouts and grade crossings. ;ighstrength

woven geotextiles can also be used to reinforce weak

subgrade soils and reduce re&uired embankment fill

materials.

Geo textiles in retaining (alls%

Cetaining walls help to maximi-e their land use.

;owever, building a concrete gravity or crib wall is often

impractical because of their high construction cost.

#eotextiles are used for a wide assortment of

reinforcement applications, including embankments over

soft soils, levees and retaining walls. #eotextiles are

wellsuited to construction of walls with timber, precast

panel and segmental block facing. $n fact a geotextile

retaining wall can be built for less than half the cost of a

conventional wall. 1oven geotextiles offer other

significant advantages

over conventional methods, such as simplified installation and construction, and the ability

to use onsite backfill material.olypropylene geotextiles cost approximately half the

amount of polyester and polyethylene geogrids, and they re&uire considerably less labor to

install.

Geo textiles s)bs)r$ace Drainage%

#eotextiles have replaced graded soil filters for drainage of

virtually all structures, including groundwater intercept

systems, pavements, building foundations, dams and walls.

6ompared to conventional soil filters, geotextiles offer

advantages by providing a consistent and continuous filter,


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reduced excavation, reduced environmental impact, simplified, higher &uality construction

and a substantial reduction in material costs.

7echanical ;ydraulic 9ongterm

erformance

ermanentdrainage function $nfluence of normaloverburden pressure ermeabilityThickness

Apparent opening

si-e (A..2.)

6hemicalproperties of water

and soil

6hemical stability

ecay resistance

Temporary

drainage function

$nfluence of normal

overburden pressure

ermeability

Thickness

Apparent opening

si-e (A..2.)

Use o$ *)te Geotextiles in Road Constr)ction

$ndia is a large producer of @ute. Dute is a low cost, renewable,biodegradable and eco

friendly natural product. Dute geotextiles are used in many geotechnical applications. A

series of field experiments were carried out by 6CC$ using @ute geotextiles for different

functions, are described as follows:

A+ *)te Geotextiles as #eparator to Impro,e a,ement er$ormance

The performance of pavements constructed on soft soils can be improved

using @ute geotextiles. Dute fabric when used as separator prevents the


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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. rovision of fabric enables subgrade develops its full bearing capacity and thus

controls rutting. Dute geotextile was used as a separator between subgrade and subbaselayers. Cesults showed negligible settlements of the pavement after six months under

traffic and no signs of surface distress observed in the treated test section.roperties of @ute

geotextile used as a separator

Description o$ roperty -al)e

Type *on E 1oven

Tensile strength '.4% k*+m

Thickness ?.3% mm

6C push through load F.> k*

$ndex puncture resistance F.FBB k*

$nplane permeability 3.' x %F8 m+s=alling cone test *o clear hole formed

=ailure strain 5F G

"+ *)te Geotextiles $or Gro)nd Impro,ement

The field subsoil was soft silty clay and the water table was F.> m below the ground level,

the whole area gets submerged during high tide. The highway constructed earlier faced

problems of subsidence of the fill during construction, excessive post construction

settlements and lateral spreading of fill material, etc. n the basis of settlement

calculations, it was estimated that as much as 5F per cent of the fill sinks into the soft

subsoil during construction itself, necessitating large &uantities of costly fill material,

thereby, pushing up the cost of construction. The problem was solved through the use of

@ute geotextiles. 7onitoring of completed embankment i.e. both treated and control stretch

showed better performance of road embankment constructed using @ute geotextile.


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Jute geotetile treated section after cyclonic rains

C+ *)te Geogrid $or .rosion Control o$ Den)ded #lopes

n the basis of field studies, conducted in the past by 6CC$, it has been concluded that

shallow sacrificial slides constitute a significant proportion of landslides in areas with

moderate rainfall intensity and where soil cover is medium cohesive in nature. 2urfacial

slides extend to only a couple of metres below the slope surface and originate as a result of

erosion from down flowing water over the denuded slopes. $f erosion is allowed to

proceed unchecked, there is every possibility that the damage may spread laterally thus

increasing the depth of erosion, eventually resulting in a much larger damaged slope area.


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D+ *)te Geotextile $or Drainage and Filtration Application

The field conditions were the stretch of hill road was located on debris slide area and

debris consists of micacious sandy silt. A number of seepage points exist on the uphi ll as

well as on downhill slopes. The road stretch was experiencing subsidence during themonsoon every year, including damages to the restraining structures. reast walls

constructed earlier had been damaged due to slip. To arrest the sinking of road pavement, a

systematic network of roadside trench drains and cross trench drains were constructed

using nonwoven @ute geotextiles. The trench drains were made of rubbles encapsulated in

nonwoven @ute geotextiles to stop the finer particle entering into the voids of encapsulated

rubbles, thereby preventing clogging the trench drains. About %FFF s&.m of nonwoven

@ute fabric having B>F gsm has been used for drainage application on about %FF m length

of road stretch. The monitoring of field experiments on this particular stretch of treated

road has shown very encouraging and satisfactory results. There has been no further

sinking and subsidence of the road at this location after three years.

Condition of road stretch after MonsoonRains

Laying of Jute geoetxtile as Trench

#eotextile in road pavement:


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Di$$erent )ses o$ Geo/Textile

Use of geotextile in Piers

Use of geotextile in e!"an#!ents

Use of geotextile in trenches and drainage


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Use of geotextile in rail road

Concl)sion:

Textiles are not only clothing the human body but also our mother land in order to protect

her. 0xtensive awareness should be created among the people about the application of

geotextiles.To explore the potential of geotextile more researches are needed in this field.

References

1. $Geotextiles, "The fabric of erosion control"[1]Accessed 20th May 200

2. $!G, "Abo#t the !G" [2]Accessed 2$th May 200

%. $&oint 'epart(ents of the Ar(y and Air )orce *1++-, "TM /1//A)&MA %210%0,

ngineering 3se of Geotextiles" 4ashington '5 [%]Accessed 2+th May 200

6. $5oletanche *online-.[6]

. $7ropex )abrics *1++6-, "Technical ote o.18 Geosynthetic )#nctions" []Accessed 2+th May

200

. $9#tay and Aydile: *200-, ")iltration 7erfor(ance of T;olayer Geotextile yste(s"

Geotechnical Testing &o#rnal, #tton ? @yton *200%-, "Geosynthetics in )lexible and igid 7aBe(ent CBerlay yste(s to

ed#ce eflection 5rac:ing"[/]Accessed 2/th May 200

10. $ATM *1++2-, "' 6/$% tandard G#ide for !dentification, torage and =andling of Geotextiles",

Ann#al >oo: of ATM tandards,

role of geotext

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