Nanjundaswamy P.Department of Civil Engineering

S J C E, Mysore

Design by

Cost and Availability

Specifications

Function

Separation

Reinforcement

Filtration

Drainage

Combined functions

Aim:

The equilibrium soil-to-geotextile systemthat allows for adequate liquid flow withlimited soil loss across the plane of thegeotextile over a service lifetimecompatible with the application underconsideration

Behind retaining walls

Around underdrains

Beneath erosion control structures

Silt fences

D

B

T

Soil subgrade

Stone base

Pavement Shoulder

GeotextileCrushed

stone/perforatedpipe underdrain

Weephole

Geotextile

H

RIVER

POND

BUILDING

GEOTEXTILE

MORAINE CORE GEOTEXTILE

ROCKFILL(CLOSURE PHASE)

(RAISING PHASE)COMPACTED

DUMPED

FILL(Draining)

SETTLEMENT

de

CO

MP

RE

SS

IBL

ES

OF

T C

LA

Y

DRAINING LAYER

H

Sediments

Geotextile

Sediment-carrying

sheet runoff

Water surface

“Clear” water

Turbid water

Mai

n s

up

por

t p

ost

s

Clo

gge

d f

abri

cF

low

H

X

h1

h2

Criteria:

Permeability

Soil Retention

Long term flow compatibility

Permeability:

Permittivity

t

k n

Soil retention:

Apparent opening size (AOS)

Filtration opening size (FOS)

dO or8595

)32(

LIN EARLYGR ADED

dl = d85dl = d50

COHESIONLESS

YES

YES YES

NO

NO

END

GAPGRADEDC ONCAVEU PWARD

INTERNALLYSTABLEIN TERNALLYSTABLE

HYDRAULIC C ONDUCTIVITY k BPLASTICITY SUSCEPTIBILITY TO CRACKINGCOHESIVEO90 40 m

UNIFORMCu 6

PERMEA BILITYk

F

2 0k

B

RETENTIO Ndl O90 3 dlRET ENTIONO 90 dl

Minimum gapsizeRisk of Piping o fFiner Particles

LEGEND :

( )( )

dl = dG ( )dl = d30 ( )dl = d30 ( )

Filter Selection

• By index tests on base soils

(Lafleur, 1999)

LINEARLYGRADED

dl = d85 dl = d50

COHESIONLESS

YES

YES YES

NO

NO

END

GAPGRADED

CONCAVEUPWARD

INTERNALLYSTABLE

INTERNALLYSTABLE

BASE SOIL GRADATION CURVE ,dl d15

HYDRAULIC CONDUCTIVITY k B

PLASTICITY SUSCEPTIBILITY TO CRACKING

COHESIVE 40 mO90

UNIFORM 6Cu

PERMEABILITY 20 kF kB

RETENTIONdl O90 3dl

RETENTIONO90 dl

Minimum gapsize

Risk of Piping ofFiner Particles

LEGEND :

( )

( )

dl = dG ( ) dl = d30 ( ) dl = d30 ( )

Modify

Aim:

The equilibrium soil-to-geotextile systemthat allows for adequate liquid flow withlimited soil loss within the plane of thegeotextile over a service lifetimecompatible with the application underconsideration

Earth dams

Drain behind and base retaining walls

Beneath a surcharge fill

Beneath railroad ballast

Capillary migration breaks

Criteria:

Permeability

Soil Retention

Long term flow compatibility

Permeability:

transmissivity

tk p

Soil retention&

Long-term flow compatibility

Same as filtration

Aim:

The placement of a flexible porous

textile between dissimilar materials so

that the integratiy and functioning of

both materials can remain intact or be

improved

Subgrade and base in roads Subgrade and ballast in railroads Foundation and embankment soil Various zones in earth dams Old and new asphalt layers Beneath Sidewalk slabs Curb areas Parking lots Sport and athletic fields

Burst resistance

Tensile strength

Puncture resistance

Impact (Tear) resistance