for prelim

7/25/2019 For Prelim

1/4

USE OF GEOSYNTHETICSFORFILTRATION ANDDRAINAGE

Functions of a FilterRetain particles of the basesoil to be lteredAvoid piping

Allow free ow of water- upstream of the lterAvoid external clogging(With unstable soils)- through the lter

Avoid internal clogging urvive constructionand environmentalstresses !unction can beprovided b" either

naturalaggregates or b"#eotextiles

Filtration Behaiour

! Clo""in"# the voids ofa medium areprogressivel" lled b"solid matter to the pointthat the passage of wateris compromised

- $ecrease in h"draulicconductivit"

! Internal clo""in"- %" mineral particles-%" precipitation and

chemical deposition inthe voids b" watercontaining iron& de-icingsalts- %" biological growthencrustation in aerobic'onditions

A$$LICATIONS #DRAINAGE

Around trench drainsand edge drains %eneath pavementbases and base courses Retaining walls andbridge abutments $rain and well pipes lope stabiliation arth dams and *evees

A$$LICATIONS #EROSION CONTROL

+rotection of runo,collection lope protection Along stream bans cour protection aroundstructures 'onstruction facilitiesacross.ad/acent to water

bodies 'ulverts& drop inlets&articial stream channels

Filter A%%lications Wrapping of trenchdrains (0oerner& 1223) Wall drains rosion protection arth and rocll dams 4ertical consolidation

drains

Granular &lter 'esi"ncriteria

a(Retention Criteria#d15( filter)d85(soil)


2/4

Retention Criteria#Oe/"eote,tile( 4 BD/soil(where;


3/4

A$$LICATIONS INFILTRATION ANDDRAINAGE EROSION CONTROL

Geote,tile &lterre-uire*ents# Retention criteria +ermeabilit" criteria Anti-clogging criteria erviceabilit" criteria $urabilit" criteria

Soil retentionA process in which theparticle movement isresisted b" granular forcesUseful 'esi"n%ara*eters

15 'oe6cient of 7niformit"& 'u85 *inear 'oe6cient of7niformit"& 'uF95 'oe6cient of

'urvature& 'c

Desi"n Charts

$etermination of soilretention re:uirementssuch asparticle siedistribution& Atterberglimits& dispersionpotential& soil densit"conditions indicating thee,ect of conning stress&are all considered anddesign charts areprepared b" Girou'

/0122(3

/0(Soil retention criteriaince drainage medium isgravel& application favors$er*ea)ilit+ ID is inthe ran"e of ?8@ an'8@

!rom chart 1eotextile apparentopening sie o2G H 15G

'uI dG@H 15Gx15Jx@5@J1H @513mm

(8) +ermeabilit" criteria!rom charts&corresponding to d1G =@5@1Jmm&0s = G(1@-G) cm.s!rom Bables& t"picalh"draulic gradient& i =

15@Kinimum allowablegeotextile permeabilit"&0g L is 0sL 15@ x (G5@x1@-G cm.s)L G5@x1@-G cm.s5

/?( Anti = Clo""in"re-uire*ents

!rom anti-cloggingre:uirements6 use

the lar"est aaila)leO186 which satises theretention criteria& or O18 7302**3Mf the geotextile is non=:oen& %orosit+ shoul')e *ore than ?7@3Mf the geotextile is:oen& percent o%enarea @

/( Suria)ilit+ Criteria

'hoose a geotextilematerial that satisesthe criteria in !ig58&corresponding tomoderate installationconditions and lowcontact stress5

/8( Dura)ilit+ Criteria7ltra violet resistance isnot expected to be aproblem owing to the

complete burial of the

geotextile5Mn addition& chemicalresistance re:uirementsare not serious& as thepermeant isuncontaminated groundwater5

Case stu'ies#Filtration Se%aration- Bitan tadium-


4/4

overlapped to provide fullcoverage over the area5

Geos+nthetics in Erosion$rotectionGeos+nthetics inSe'i*ent an' ErosionControl

Mntroduction and

Applications What is itN rosion control is ameans of eeping a soil inplaceor catching a soil after ithas been displaced butbefore it moves into

surface waters5

;h+ Is It Nee'e'K

Bhere are public lawsthat ; preclude the polluting ofsurface waters withsediments preserve topographicintegrit" preserve soil for farming preserve foundationintegrit" for structuresfounded on soil5

;here Is It Nee'e'K

Mt is needed onconstruction andagricultural sites andnatural places wherewater causes soils todisplace5 Mn short; where soil and

moving waterinteract at the ground

surface

Factors Inuencin"T+%es of Erosion

! RainfallMin'uce'erosion factors#

intensit+ an''uration of rainfall slo%e of lan' soil t+%e

All a,ect the amount oferosion and the erosioncontrol measuresselected5

! Shoreline erosionfactors#

soil t+%e :ae hei"ht )each slo%e 'uration an'intensit+ of stor*

All a,ect the amount oferosion5

! Scour#

O Bhe amount of scour&around bridge piers forexample& is a,ected b"pier shape& depth ofstream& storm durationand channel shape& inaddition to soil t"pe5

Strate"+

'hoose least costl"erosion control measureand ealuate#O *

for prelim

Documents