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Dr.G.Venkatappa Rao
Geosynthetics
• Construction Material – compare with cement & steel
• Is a Technology - Engineering with Geosynthetics
• Process of development
• Technology groups involved – Polymer,
Textile
Civil
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Historical - Roads
• Use of coconut leaf mattresses in Kerala in road construction
• Dragging a bogged down vehicle using leaves, brushes etc
• Cordruoy roads using tree trunks packed next to one another and levelling with gravel for traffic in forest areas
• Natural erosion control by vegetation – turfing, trees etc
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Geosynthetics
• Modern civil engineering construction
materials
• Modify/Improve soil/geologic material
behaviour
• Developed/Synthesized for specific function
or application in construction
• More than 1billion sq m annual use
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GEOSYNTHETICS
• They generally replace scarce raw material
resources like steel/cement/aggregates
• They are good alternatives to conventional
designs
• They are, sometimes, the only means of
construction
• They can be rapidly installed
• They can revitalise textile industries ???
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27 July 2016 Geosynthetics - Introduction G V RAO
What Are Geosynthetics?
A planar, polymeric (synthetic or natural) material used in contact with soil/rock and/or any other geotechnical material, for Filtration, Drainage, Separation, Reinforcement, Protection, Sealing and Packing.
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Geosynthetics –The wide variety
• Geotextiles –Woven, non-woven Filter fabrics
• Geogrids
• Geomembranes
• Geocomposites
• Geonets, Geofibres,mesh mattings, Geopipes
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27 July 2016 Geosynthetics - Introduction G V RAO
What Are Geotextiles and Related Products ?
Geotextile
A planar, permeable, polymeric (synthetic or
natural) textile material, which may be nonwoven,
knitted or woven, used in contact with soil/rock
and/or any other geotechnical material in civil
engineering applications.
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Continuous filament extrusion (after American Hoechst Corp.)
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Flat Loom 19
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Woven or Knitted Geotextiles
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27 July 2016 Geosynthetics - Introduction G V RAO
Scanning electron micrographs of (2X1) twill weave monofilament fabric
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Woven geotextile
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Scanning electron micrographs at interlacement point of woven fabric
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27 July 2016 Geosynthetics - Introduction G V RAO
A nonwoven geotextile in the form of a manufactured sheet, web or batt of directionally or randomly orientated fibres, filaments or other elements, mechanically and/or thermally and/or chemically bonded. Nonwovens are used in Filtration, Drainage, Separation, Protection and/or Erosion Control applications.
(Protection) 30
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The needle punching process (after American Hoechst Corp.)
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Typical barbed needle (after American Hoechst Corp.)
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Basic principles of needle punching process 33
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Non-woven Geotextile
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Scanned electron micrographs of spun bonded fabric with different amplification
A 36
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B 37
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C 40
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Geogrids
A planar, polymeric structure consisting of a
regular open network of integrally connected
tensile elements, which may be linked by
extrusion, bonding or interlacing, whose
openings are larger than the constituents,
used in contact with soil/rock and/or any
other geotechnical material in civil
engineering applications.
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Geogrid Manufacture 27 July 2016 Geosynthetics - Introduction G V RAO 42
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Uniaxial Geogrid
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Uniaxial Geogrid
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Geogrid Biaxial 27 July 2016 Geosynthetics - Introduction G V RAO 44
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Extruded Geogrids
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Woven or Welded Geogrids
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Geonet
• A planar, polymeric structure consisting of a
regular DENSE network, whose constituent
elements are linked by knots or extrusions and
whose openings are much larger than the
constituents, used in contact with soil rock
and /or any other geotechnical material in civil
engineering applications (IGS)
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Geonet
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Geomembrane
• A planar relatively impermeable, polymeric
(synthetic or natural) sheet used in contact
with soil/rock and/or any other geotechnical
material in civil engineering applications
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27 July 2016 Geosynthetics - Introduction G V RAO
A planar, relatively impermeable, polymeric (synthetic) sheet with a minimum thickness of 1.0 mm. In landfill applications they are usually manufactured of HDPE with a thickness of > 1.0 mm, in Germany > 2.5 mm. The surface can be smooth, profiled or textured and can be of importance for the shear behaviour.
Geomembrane
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Geocomposites
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27 July 2016 Geosynthetics - Introduction G V RAO
Manufacture of GCLs Cont’d
Adhesive mixed with clay 63
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Geomat
A three-dimensional, permeable, polymeric
structure, made of bonded filaments, used to
reinforce roots of grass and small plants and
extend the erosion control limits of vegetation
for permanent erosion control applications.
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Geosynthetics - Introduction
G V RAO
Geosynthetics – composition
• Polypropylene
• H D P E
• Polyester
• PVC
• Synthetic Rubber
• Natural fibres – Jute, coir
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COIR GEOTEXTILES
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Rolls of RECBs
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Geosynthetics – the functions
• Separation
• Drainage
• Filteration
• Reinforcement
• Moisture barrier
• Cushion
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What is Separation?
Definition
• A Geosynthetic placed at the interface between
two dissimilar geotechnical materials functions
as a Separator when it prevents these materials
from mixing under the action of applied loads
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Separation function
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Separation Applications Typical Application of Geosynthetics as Separators
• At sub-grade/sub-base interfaces in temporary and permanent roads
• Between railroad ballast and a foundation soil
• Between embankment fill and soft foundation soil
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27 July 2016 Geosynthetics - Introduction G V RAO
Difference between two different soil
types
Filtration and Separation
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.Nonwovens are used in Filtration, Drainage, Separation, Protection and/or Erosion Control applications.
Filtration and Separation
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Drainage function
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Geosynthetics - Introduction G V RAO
Typical Applications (1)
BUILDING DRAINAGE GARDEN ROOF
ROAD EDGE DRAINS HORIZONTAL ROOFING
FINDRAINS PARKING DECKS
RETAINING WALLS PLANTERS
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REINFORCEMENT FUNCTION
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Geostrip
• A polymeric material in the form of a
strip, used in contact with soil/rock
and/or any other geotechnical material
in civil engineering
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Reinforcement function
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Function vs. Geosynthetic Type Type of
Geosynthetic Separation Reinforcement Filtration Drainage Containment
geotextile geogrid geonet geomembrane geosynthetic clay liner
geopipe geofoam geocomposite
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First Reinforced Soil Wall in
India – Ludhiana, Punjab - 1986
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The Designed
Section
BS 8006 1995
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reinforced soil
segmental facing units
geosynthetic reinforcement
layer
foundation soil
geotextile wrapped drain
granular
levelling pad
retained soil
shear key or
mechanical
connector
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Blockwork wall in S E Asia
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0
100
200
300
400
500
600
700
800
0 2 4 6 8 10 12 14
Height of wall (m)
Koerner et al. 1998
Gravity
Walls
Crib / Bin Walls
MSE (Metals)
MSE (Geosynthetics)
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Placement patterns for reinforcement
(a) Even spaced-even length (b) Uneven spaced-even length
(c) Even spaced-even length with short facing layers
(d) Even spaced-uneven length with short facing layers
(One that Failed)! (With Reinforcement-Steep & Stable) 27 July 2016 Geosynthetics - Introduction G V RAO 99
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3rd European Conference on Geosynthetics 27 July 2016 Geosynthetics - Introduction G V
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Stiff uniaxial
geogrid 40
and 55 kN/m
10.4m
Geosynthetic materials
Geocell mattrace : Uniaxial stiff geogrid 80 kN/m Biaxial geogrid 30 kN/m
Vertical prefabricated drains: Width 100mm, Thickness 3 mm PP filter, Tensile strength 2.2kN Discharge capacity buckled 50.10--6 m3/s
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Placing Fill on Geotextile
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Soft soils in construction
- low bearing capacity
- excessive rutting
- compressible layers
- landslides
- slope failure
- uneven settlements
- …
soil reinforcement needed !
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sub soil
Stabilization of ballast layer
Ballast Sub-base
geogrid
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Hydraulic Engineering Applications
Waterproofing of Dams
Waterproofing of Canals
Reservoir Liners/Floating Covers
Tunnel Waterproofing & Rehabilitation
Pipe Rehabilitation & Remediation
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Waterproofing of Dams
masonry, concrete, earth and RCC dams
GM is not a structural element, its waterproofing
many dams over 50-years old often have leakage; sometimes excessive leakage
methods are under rapid development mainly in European Alps and in China
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(Concrete Dam Leaking!)
(Completed Concrete Dam Lining) (Lined Earth Dam: Before Rip-Rap)
(Lining a Concrete Dam)
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LINING SYSTEMS
Canal and Pond Lining
(Lined Pond) (Aerobic Decomposition of Waste) 27 July 2016
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Embankment over Soft clay
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Reinforcement: Full width or localised areas
Soft Clay Foundation
Embankment Fill
Reinforcement tension develops as a vector of these forces
Tr Tr
Beware of ditches in this area!!!
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Maintenance of Silt Fences
• Inspection - physical condition, depth of soil behind fence, base pullout, fabric condition
• Clean-out when half-full.
• Allow soil to overtop and install additional downhill fences
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Silt Fence - Installation
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Geosynthetic in Waste Containment
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Function vs. Geosynthetic Type Type of
Geosynthetic Separation Reinforcement Filtration Drainage Barrier
geotextile (WGT) (NWGT) (NWGT)
geogrid geonet geomembrane geosynthetic clay liner
geopipe geofoam geocomposite
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Summary
Geosynthetics are bona fide engineering materials - MORTH, IRC
Test methods and designs are available – BIS, ASTM, BS
Basic advantage is quality control of factory manufactured products
Construction Quality by rigorous CQC/CQA
Field performance has been excellent
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A presentation by
Sai Master
Geoenvironmental Services
Private Limited
Serving the EnvironmentSAI MASTER ACHARYA SRI EKKIRALA BHARADWAJA
THANK YOU
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Web Sites of Geosynthetic Organizations
• Geosynthetic Institute (GSI) <http://www.geosynthetic-institute.org>
• International Geosynthetics Society (IGS) <http://www.igs.rmc.ca>
• Geosynthetics Materials Association (GMA) <http://www.gmanow.com>
• International Standards Organization (ISO) <http://www.iso.ch/iso/en/ISOOnline.frontpage>
• ASTM International <http://www.astm.org>
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