5 overview geosynthetics

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1 APPLICATION OF GEOTECHNICAL ENGINEERING CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur GEOTECHNICAL ENGINEERING GEOSYNTHETICS CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur Mechanically Stabilised Wall CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur Mechanically Stabilised Wall CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

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Page 1: 5 Overview Geosynthetics

1

APPLICATION OF GEOTECHNICAL ENGINEERING

CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

GEOTECHNICAL ENGINEERING GEOSYNTHETICS

CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Mechanically StabilisedWall

CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Mechanically StabilisedWall

CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 2: 5 Overview Geosynthetics

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Geosynthetics

• What are geosynthetics?

• Why would we want to use them?

CE451A Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• How should we use them?

Geosynthetics

Geosynthetics are human‐made materials made from various types of  polymers used to enhance, augment and make possible cost effective environmental, transportation and geotechnical engineering construction projects. 

Reasons for the development of new geosynthetic products

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reasons for the development of new geosynthetic products

• They are quality control manufactured in a factor environment.• They can be installed rapidly• They generally replace raw material resources• They generally replace difficult design using natural materials• They are generally cost competitive against natural soils that they replace

• They are actively marketed and widely available 

Basic functions of Geosynthetics

Seperation

Drainage

Filtration

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reinforcement

Protection

Containment

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Separation

Drainage

Page 3: 5 Overview Geosynthetics

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Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Filtration

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reinforcement

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reinforcement

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Seepage barrier

Page 4: 5 Overview Geosynthetics

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Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Lateral restraint

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Bearing capacity improvement

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geomembrane tension

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reflection cracking

Page 5: 5 Overview Geosynthetics

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Basic functions of Geosynthetics

Primary Functions

• Containment• Drainage• Filtration• Separation

• Site constraints• Tight time schedule• Max. usage of locally available resources

• Least environment impact

New challenges ! !

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

The use of geosynthetic materials has two aims:1) To do the job better (no deterioration of material or excessive leakage)

2) To do the job more economically (either through lower initial cost or through durability and longer life, thus reducing maintenance costs)

• Reinforcement• Combination of above

• Least environment impact• Long term performance • High cost effective ratio

Major applications of Geosynthetics

• In Roads and Pavements: S b d ti d

• In Subsurface Drainage:

• In Engineered landfills:– Reinforcement of covers– Hydraulic barriers– Gas and leachate collection

system

• In Reinforced Soil Systems: – Embankments over soft

foundations, – Reinforced Steepened

slopes, – Reinforced soil walls.

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

– Subgrade separation and Stabilization,

– Base Reinforcement, – Overlay Stress Absorption

and Reinforcement.

In Subsurface Drainage: – Subgrade dewatering, – Road base drainage, – Structure drainage.

• In Erosion and Sediment Control– Hard Armor Systems,

Silt Fence.

• In Seepage control systems– Structure water proofing, – Environmental Protection.

Geosynthetics

How to emphasize the reinforcement effect?

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Separation

Page 6: 5 Overview Geosynthetics

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Prior to Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Basic functions of Geosynthetics

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geosynthetic Reinforced Segmental Retaining Walls

a) base sliding b) overturning c) bearing capacity (excessive settlement)

External

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

d) pullout e) tensile over-stress f) internal sliding

h) column shear failure i) topplingg) connection failure

Internal

Facing

Geosynthetic Reinforced Segmental Retaining Walls

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 7: 5 Overview Geosynthetics

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Geosynthetic Reinforced Segmental Retaining Walls

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Material bowl and vibrator charge

Geogrid coating

Insertion of vibrator with

geogrid

Pull-out of vibrator,

adding material and compaction

Column is completed

Geosynthetic Encased Stone Columns

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geosynthetics Reinforced Soil Barriers

Membrane effect

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geosynthetics Reinforced Soil Barriers

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

1.2m thick URSB having overburden pressure equivalent of landfill cover systems

1.2m thick GRSB having overburden pressure equivalent of landfill cover systems

350mm

220mm

Page 8: 5 Overview Geosynthetics

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Flexible Geosynthetics Sand ContainersCE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

GeosyntheticsCE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Polymers used in GeosyntheticsCE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Chemically linked large molecules of carbon atoms with hydrogen or other atoms attached

• Polypropylene

• Polyethylene

• Polyester• Polyester

• Polyamide

• Polystyrene

• Poly Vinyl Chloride

PP/Polyester /PE Geosynthetics – Most widely used across the Globe  (more than 95 percent) 

Geotextiles

Geotextiles are flexible, textile‐like fabrics of controlled permeability used to provide filtration, separation or reinforcement in soil, rock and waste materials

CHARACTERISTICS 

• Can be used for Separation, Reinforcement Filtration Drainage

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Reinforcement, Filtration, Drainage.• Porous and allow flow of water through it.• Composed of polymers like polypropylene, high density  polyethylene, polyester

• They may be either woven or non woven

Woven Geotextiles Non‐woven Geotextiles

Page 9: 5 Overview Geosynthetics

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Geotextiles

GeotextilesSamples

http://en.wikipedia.org/wiki/File:Geotextile-GSI.JPG

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Coir Geotextiles

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geomembranes

Geomembranes are very low permeability synthetic polymeric sheets used as membrane liner or barrier for liquid or solid waste containment systems

CHARACTERISTICS 

• Can be used for waste containment.

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• Relatively impermeable (1x10‐12 to 1x10‐15

m/s) when compared to clayey soil.• Composed of polymeric materials like HDPE, LDPE, VFPE, PVC, PP

• Available in smooth and textured surfaces.• These sheets are prefabricated in factory and transported to the job site, where placement  and field‐seaming are performed to have complete isolation 

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 10: 5 Overview Geosynthetics

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Geosynthetic Clay Liner (GCL)

GCLs are very low permeability liner consists of a thin layer of bentonite clay sandwiched between two geotextiles or glued to geomembranes,  primarily used for solid waste containment systems

CHARACTERISTICS 

• Can be used for waste containment and water proofing

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

water proofing.• Relatively impermeable (1x10‐10 to 1x10‐12

m/s) when compared to clayey soil.• GCL contain approximately 5 kg/m2 of bentonite.  It helps in self‐sealing at overlaps between panels ‐ when water hydrates the clay in GCL, the clay swell and automatically seal the overlap. 

• These sheets are prefabricated in factory and transported to the job site, where placement  and overlapping are  done.

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

GCL samples

Geogrids

Geogrids are planar structure formed by a regular network of tensile elements with apertures of sufficient size to allow interlocking with surrounding soil

CHARACTERISTICS 

• Can be used for reinforcement. • Geogrids are formed either stretched in

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• Geogrids are formed either stretched in one (uniaxial geogrids) or two directions (biaxial geogrids) for improved physical properties or made on weaving machinery by unique methods.

• It has high dimensional stability and high tensile modulus at very low elongation.

• Basic load transfer occurs in the form of passive earth pressure on transverse element of geogrid and interlocking of grain particles in geogrids. Uniaxial geogrid Biaxial geogrid

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 11: 5 Overview Geosynthetics

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Geocells

Geocells are three‐dimensional, expandable panels made from HDPE or polyester strips used for cellular confinement systems.

CHARACTERISTICS 

• Can be used for tensile reinforcement and shear resistance to increase the bearing 

it f b d d il

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

capacity of subgrade and cover soil.  • Comprises of high strength plastic network (3D) with soil filled within the cell. 

• Internal cells transform into reinforcement and confined soil builds compression  inside the structure.

• Cellular confinement systems improve the structural and functional behaviour of soil infill materials

• Re‐useable / Recyclable  

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geonets

Geonets are planar structure consisting of integrally connected parallel sets of ribs overlying similar sets at various angles for planar drainage of liquids or gases.

CHARACTERISTICS 

• Can be used for in‐plane drainage. • Available in bi planer and tri planar

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• Available in bi‐planer and tri‐planar geonets. Tri‐planar geonets resists vertical compression under load and allow larger in‐plane flow. 

• Because of its open structure, it must be protected from becoming clogging by soil or adjacent materials.

• Hence, in most cases it must be used along with geotextiles which forms geo‐composites.

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geonet samples

Page 12: 5 Overview Geosynthetics

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Geopipe

Geopipes are polymeric based geosynthetic material consisting of flexible plastic pipes  which are placed beneath the ground surface and subsequently backfilled .

CHARACTERISTICS 

• Can be used for underground pipeline transmission of water gas oil and various

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

transmission of water, gas, oil and various other liquid. 

• It  may be made of PVC, HDPE, PP, Cellulose Acetate Buytrate. 

• It can be solid wall or corrugated.• Mainly used in leachate collection system to facilitate collection and rapid drainage of the leachate to the removal system.

• In Bioreactor landfills it can be used to transport and redistribute of leachate

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geocomposite

Geocomposites represents a subset of geosynthetics whereby the best features of different geosynthetic materials are combined to solve the specific problem in the optimal manner.

CHARACTERISTICS 

• Can be used for enhanced performance in separation reinforcement filtration

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

separation, reinforcement, filtration, drainage and containment.

• Geotextile‐geonet composites: improved drainage, separation and filtration 

• Geotextile‐geomembrane composites: enhance resistance to puncture and tear

• Geotextile‐geogrid composites: enhance drainage and mechanical strength

• Geomembrane‐geogrid composites: same polymer‐enhanced strength and friction

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 13: 5 Overview Geosynthetics

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Summary of Type and Function of Geosynthetics

Type S D F R B P

Non woven geotextiles + * + +WovenGeotextiles

+ * +

Geogrids +b

S - SeparationD -DrainageF - FiltrationR - ReinforcementB - BarrierP P t ti

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geomembranes +Geocells + +GCL + *Geonet +Geopipe +Geocomposite * + * * + +

P - Protection

+ Main Function* Secondary

Function

Role of Geosynthetics in Engineered MSW Landfills

geopipe

Cover system

Side lining system Hydraulic barrier /

can be replaced with geomembrane or GCL

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

geopipe

g p p

Base lining system

Hydraulic barrier / Geomembrance / GCL

*Adopted from Lecture notes on Landfills from Prof. Gourc, LTHE, Grenoble, France

GCL with geotextiles

Subgrade soil

Geocomposite

Geomembrane

Typical Landfill Base-Lining System

Geomembrane

Geocomposite

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Typical Landfill System prior to Closure

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Page 14: 5 Overview Geosynthetics

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Needle punch non-wo en geotextiles

GCL with geotextilesGeomembrane

GeocompositeCover soil

Daily cover soil

Geogrid

woven geotextiles

Typical Landfill Cover SystemCE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Comparison

Component Soil Geosynthetic Product

Drainage layer Coarse grained soils Geonet, Geocomposite

Filter layer Coarse grained soils Geotextiles

Hydraulic barrier Clay soil Geomembrane, 

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Geosynthetic Clay Liner

Gas transmission layer Coarse grained soils Geotextiles, Geocomposite

Protection layer Fine grained soils Geotextiles, Geogrid

Erosion  Fine grained soils Geogrid, Geonet,  Geocell

Overview of Geosynthetics

• Geotextiles ‐ flexible, textile‐like fabrics of  controlled permeability used to provide filtration,  separation or reinforcement in soil, rock and waste  materials

• Geomembranes ‐ essentially impermeable  polymeric sheets used as barriers for liquid or solid  waste containment

• Geogrids ‐ stiff or flexible polymer grid‐like sheets with large apertures

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• Geogrids ‐ stiff or flexible polymer grid‐like sheets with large apertures used primarily as reinforcement  of unstable soil and waste masses

• Geonets ‐ stiff polymer net‐like sheets with in‐plane openings used primarily as a drainage material  within landfills or in soil and rock masses 

• Geosynthetic clay liners ‐ prefabricated bentonite clay layers incorporated between geotextiles and/or  geomembranes and used as a barrier for liquid or solid waste containment

• Geocomposites ‐ hybrid systems of any, or all, of the above geosynthetic 

types to solve the specific problem in the optimal manner

Major Concerns

Major issues related to long‐term performance of geosynthetic products in waste containment systems are:

• Lifetime of Geosynthetic products

• Interface friction

D i ti f GCL

CE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

• Desiccation of GCL

• Waves (or Wrinkles) in GMs

• Wind Uplift

• Seams and Details

• Chemical Resistance

• Biological Clogging

• QC/QA

Page 15: 5 Overview Geosynthetics

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Slope failureGM Wrinkles and desiccation Desiccation of GCL

Snap-shots of Failures of Geosynthetic ProductsCE451A : Dr. Rajesh Sathiyamoorthy, IIT Kanpur

Wind uplift Differential settlement Chemical attack

Wrinkles and tear of GM Geocomposite Blowout of GM