5 overview geosynthetics
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geotechTRANSCRIPT
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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