geo textile as filters and separator

8/12/2019 Geo Textile as Filters and Separator

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BYKRISHNAN.C

UVARAJ.D


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The protection of groundwater and surfacewater is now a major consideration in thedesign of waste containment facilities in manycountries.Geo-synthetics play an important role in thisprotective task because of their versatility,cost-effectiveness, ease of installation, andgood characterization of their mechanical andhydraulic properties.Furthermore they can offer a technicaladvantage in relation to traditional linersystems or other containment systems.


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eo synthetics are fabric like materialmade from polymers such as polyester,polyethylene,polypropylene,polyvinylchloride(PVC),nylon,chlorinated

polyethylene, and others.


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Drainage The fabrics can rapidlychannel water from soil to variousoutlets.Filtration When placed betweentwo soil layers, one coarse grained and

the other fine grained, the fabric allowsfree see page of water from one layer tothe other.


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Separation Geotextile help keepvarious soil layers separate afterconstruction for example, in theconstruction of highways, a clayey subgrade can be kept separate from a

granular base coarse.Reinforcement The tensile strengthof geotextile increases the load

bearing capacity of the soil.


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Function Natural Soil Geosynthetics

Barrier-Single CCL GM

Barrier-Composite

GM/CCL GM/GCL

GM/GCL/CCL

Drainage Layer Sand

Gravel or sand

GT

GN

Filter Layer Sand GT


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GT

GG

GN

GCL

GM

CCL

Gravel w/perforated pipe


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Solid Waste


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THE UPPER FILTER GEO TEXTILE

MINIMIZE THE MIGRATION OFSOLIDS FROM THE WASTE WHILEPERMITTING LIQID TO PASSTHE LOWER SEPARATOR GEO TEXTILE

TO MINIMIZE INTERMIXING OF FINEGRAINED LINER MATERIAL AND THECOARSE GRAINED DRAINAGE STONE


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IT SHOULD SATISFY THREEREQUIREMENTS:SOLID RETENTION CAPACITYSUFFICIENTLY PERMEABLESUFFICIENT RESISTANCE TOCLOGGING


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Strategies to decrease degree of cloggingGeo textile has BUFFERING EFFECT todecrease the rate of permeabilityProtect the geo textile from damageduring placement of few layers of wasteClogging may be reduced by adding antimicrobial agent of geotextile materialBy selecting high percent open area


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Construction damage is possible due toPuncture of coarse granular material fromtearing due to action of heavy machineryRupture from sub grade settlements

this can be minimized byUsing low modulus geo textileBy appropriate sub grade preparation


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The design of separator layer betweendrainage layer and under laying finegrained natural or compacted soil is morestraight forward and follows conventionaldesign


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Synthetic drainage mats are waffled net(

geo nets) they are structure to includeopen channel flow for in planeconveyance of relatively large fluids

The mats are used in conjuction withupstream filter and downstream geo-membrane barrier


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They restrict the movement of soil particlesinto open channelPrimary design consideration of mats are

flow capacity and conductivityleachate collectionleak detection layers


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Flow is turbulentCapacity depends on

Hydraulic gradient

Actual materials flow rateMat compression due to overburdenloadsCompression induced creep

Mat material and thicknessTemperature and viscosity of flowing fluidDirectional drainage characteristics


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Leak detection rates are governed byconductivity of mats and dimension of flowpath


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Under certain hydrological and

geotechnical conditions, natural orcompacted clay barriers are unable toprovide required level of environmentalprotection from landfill contaminantsThe use of geo membranes ascomplimentary barrier may provideeconomical means of obtaining additionalprotection to meet regulatory standards


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There are two mechanisms of contaminanttransportation through geo-membraneMolecular diffusion under hydraulicgradientLeakage through holes under hydraulicgradient


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a landfill capping is used to control theamount of leachate generation by rainfallinfiltration

It consists of geo-membrane barriersynthetic drainage mat for rainfall collectionGeotextile filter between drainage mat and

final soil coverDrainage layer for transmission of gases tohigher vent


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Tensile force will be mobilized in geosynthetic components lining the side slopedue to waste overburden load, waste

settlement and consolidation, self weight ofgeo synthetic componentsMethod of evaluation of tensile forces-Equilibrium method(requires frictioncharacteristics)Tension is anchored at the top of the slope


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Differential settlement and localizedsettlement occurs at soft zonesOpen voids may develop due to tension

cracking, karstic collapse or soil dissolutionSo to overcome this the geo-syntheticmembers must have sufficient strength tobridge the voids

High safety of factors are used since strengthmay be lost during damage in installation


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Long term creep and degradationexpected. This is also due to UV exposureChemical reaction with leachate, swellingdue to chemical adsorption, extraction,oxidation and biological attacksCompatibility of geosynthetics with the

landfill gases must be ensured


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The severity of the degrading mechanismswill govern the service life of the membersThe installation damage, magnitude of

imposed mechanical stresses andsynergism with the various mechanismmay increase the rate of degradationThe service lifetime of various geo-membranes are rarely in excess of 30years

geo textile as filters and separator

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