Post on 04-Feb-2018
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CE5350Geos nthetics
&
Reinforced
Soil
Structures
NPTELVideo:GeosyntheticsandReinforcedSoilStructures
http://www.nptel.iitm.ac.in/courses/105106052/
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withsoil
in
geotechnical
constructions.
Natural:coir,
jute,
hemp,
etc.
Artificial: ol mericormetallic
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TYPES OF GEOSYNTHETICS Geotextiles
Geogrids Geonets
Geomembranes
Pre-fabricated vertical drains PVD
Geosynthetic Clay Liner (GCL)
- Geocomposites & Geo-others
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Graphical symbols proposed by IGS
letter
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Letter Symbols for
Different Functions of Geosynthetics
B Barrier (fluid)D Drainage
E Surficial Erosion Control
F FiltrationP Protection (of geomembranes)
R Reinforcement
S Separation
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FlexibleBreakwaterunitmadeof
geosyn e cs
eac
san
e
ags
inropenetgabions
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REINFORCED SOIL
Soil+reinforcement=reinforcedsoil
Reinforcement:Ancient:Treebranches,grassreeds,straw,rootsof
v g , , u
Modern: Steel,polymeric,naturalmaterials
tension
Combinedproducthasmuchbetterengineeringproperties
v u
u Reinforcedsoilconceptissimilartothatofreinforced
concrete
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Need for Retaining Walls
o as g compress ve strengt ut m te
tensile and shear strengths
repose Stee er slo es re uire lateral su ort
Purpose of the retaining walls is to provide lateral
support to the soil to make it stand at steep anglesInitialsoilposition
withsteepslope
Finalslope
at
angleofrepose
cv
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Unreinforced
Embankments
slope
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Reinforced Soil
m an men s
slope
Stee
reinforced
spacegained
slope
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Conventional
Retainin
Walls
MasonrygravityretainingwallReinforcedconcretesemigravityretaining
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Componentsofreinforcedsoilretainingwalls
layers
ac soac ng
panelsLevelling pad
-
Levelling pad is usually 150 mm thick and 300-400 mm wide
Backfill soil is select non-plastic fgranular fill
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Constructionofairportat
13
,
Ms/
Maccaferri India
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14Constructionof
33
m
high
embankment
at
Shillong
bypass
Road
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Brief history of MSE Walls in India
First
MSE
wall
in
mid
1980s
at
Ludhiana MostRoBs onNHAIprojectsbuiltusingthistechniques
VerycommontoseeMSEwallheightsmorethan10m
Geosyntheticsand
steel
ladders,
steel
strips,
plymeric
s r ps,anc orsys emsuse as ma er a s
Soilandflyashusedasbackfillmaterial
OneprojectcurrentlyunderwayinSikkimwithheight
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DifferentTypesofREWallsbuiltinIndia
Fullheightwalls Modularblockwalls Panelwalls
Steelmeshreinforcement Steelstripswithanchor Gabionfacings
Geogridreinforcement Polymericstripreinforcement16
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View of 2-tier Wall from Krishna River17
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Topviewofthecompleted4tierwall18
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Viewof
the
additional
parking
space
gainedatthetopofthehill
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Bituminous wearing course
Base course
TSub-base course
Subgrade soil
Thickness of the pavement (T) depends on the
s reng o su gra e so , ra c oa ng, es gn e,
properties of layers
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WBM material
WBM
GSB
WBM & GSB Layers in a flexible pavement
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T ical Granular sub-base GSB la er in a flexible avement
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aggregatelayergeotextileseparator
subgrade
soil
Prevents the intermixing,
prevents piping, strength of
aggregate is preserved
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Drainagefunctionofageotextilelayer
ingressofwaterintopavementlayers
flowofwaterflowofwater
ra n
Thick geotextile with good drainage properties is
used at interface
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FiltrationFunction
Geotextilelayeractingas
a
filter
Watercomingoutleavingbehind
the
fine
soil
particles
intact
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Conceptual representation of filtration phenomenon
Larger particles have
arger n er-par c e
space
Filter layer(s)
Flow
direction
Base soil
Pore pressure dissipation through soil
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Simpleexplanationofthefilter
Tea filter should allow the
passage of liquid tea whileretaining the tea powder
If the openings in the filter are
large, tea powder will flowroug , w c s un es ra e
If the filter openings are too,
through freely, which is also notdesirable
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Geogrid reinforced pavement construction
wrinkles in the geosynthetic
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BackDumpingAggregate
Minimum cover of 150 to 200 mm soil above geosynthetic
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Geocell reinforcedflexiblepavement
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Compact the Aggregate
using suitable compaction equipment.
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Cover system
GL GL
as e e -up n ayers
with alternate soil layers
Liner system
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Barrier concept in landfills (Gartung 1996)
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typesofgeosynthetics
yp ca crosssec ono a an w eren ypeso geosyn e cs
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Hindustan Zinc Factory, Visakhapatnam
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Embankment was constructed using the granules
o zeros e m xe w murum so
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reinforcement used to maintain steep slopes
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Linin of the surface with HDPE eomembrane
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Spreading the geomembrane layer down the slope (notice
the joints along the slope and not across the slope)
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Rolls of geomembranes ready to be rolled on the landfill slopes
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Leak testin of eomembrane seams
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ATNSCB
House
lost
into
sea
due
to
coastal
erosion
in
May
2012
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Dee ulle s formedonhi hwa slo esb rainwater
inducederosion noticethefinesilty soilwhichishighly
susceptibleto
erosion
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ew o e an a er cover ng w vege a on
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Use of coir mat to
promote vegetation
growth to preventsurface erosion
54/48Geosynthetics - Introduction
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UseofstonefilledropenetgabionsforshorelinestabilizationatSwami
ara n emp e, a , u ara
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ComponentsoftheGrassPlant(Hall1992)
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InnovativeuseofgeogridsforshoreprotectionatNavi Mumbai
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S . No. Topic Approx. no. o c asses1 Introduction to course and different types
of geosynthetics & applications
3
2 Principles, concepts and reinforcement 4
Mechanism
3 Types of polymers and manufacture of
geosynthetics
2
4 Determination of ro erties of 7
geosynthetics
5 Design of road bases and earth beds using
geosynthetics
5
7 Design of reinforced soil embankments 6
8 Soft ground improvement using PVDs &
other geosynthetics
3
pp ca ons o geosyn e cs n an s
10 Case studies & summary of course 2Total 41