dr.g.venkatappa rao - iit gandhinagar and... · dr.g.venkatappa rao ... basic principles of needle...

27-Jul-16

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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

27 July 2016 Geosynthetics - Introduction G V RAO 2

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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


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 ???


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



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



Scanning electron micrographs of (2X1) twill weave monofilament fabric

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Woven geotextile


Scanning electron micrographs at interlacement point of woven fabric

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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


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


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


Uniaxial Geogrid

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Geogrid Biaxial 27 July 2016 Geosynthetics - Introduction G V RAO 44

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Extruded Geogrids


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)


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



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



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.


Geosynthetics - Introduction

G V RAO

Geosynthetics – composition

• Polypropylene

• H D P E

• Polyester

• PVC

• Synthetic Rubber

• Natural fibres – Jute, coir

27 July 2016 66

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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


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



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

27 July 2016 79


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


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


First Reinforced Soil Wall in

India – Ludhiana, Punjab - 1986


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The Designed

Section

BS 8006 1995

90


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27 July 2016

Geosynthetics - Introduction G V

RAO

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

RAO

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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

3rd European Conference on Geosynthetics 27 July 2016 Geosynthetics - Introduction G V

RAO

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Placing Fill on Geotextile


27 July 2016

Soft soils in construction

- low bearing capacity

- excessive rutting

- compressible layers

- landslides

- slope failure

- uneven settlements

- …

soil reinforcement needed !


RAO 103

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sub soil

Stabilization of ballast layer

Ballast Sub-base

geogrid

27 July 2016


RAO 104

Hydraulic Engineering Applications

Waterproofing of Dams

Waterproofing of Canals

Reservoir Liners/Floating Covers

Tunnel Waterproofing & Rehabilitation

Pipe Rehabilitation & Remediation

27 July 2016


RAO 105

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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

27 July 2016


RAO 106

(Concrete Dam Leaking!)

(Completed Concrete Dam Lining) (Lined Earth Dam: Before Rip-Rap)

(Lining a Concrete Dam)

27 July 2016


RAO 107

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LINING SYSTEMS

Canal and Pond Lining

(Lined Pond) (Aerobic Decomposition of Waste) 27 July 2016


RAO 108

Embankment over Soft clay


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


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

27 July 2016 118 Geosynthetics - Introduction G V RAO

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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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