GeosyntheticsWhat are Geosynthetics? GEO Soil, Rock or other Geotechnical material SYNTHETIC Man made Polymeric material Used to enhance, augment and make possible cost effective construction

Geosynthetics

Nanjundaswamy P.

Dept. of Civil Engineering

S J C E, Mysore

What are Geosynthetics?

GEO

Soil, Rock or other Geotechnical material

SYNTHETIC

Man made

Polymeric material

Used to enhance, augment and make possible cost effective construction

Polymer - Types & Materials

Polypropylene(PP)

Polyethylene (HDPE, LDPE, LLDPE)

Polystyrene (PS)

Polyvinyl Chloride (PVC)

Polyamide (PA) eg. Nylon

Polyester

Acrylonitrile Butadiene Styrene (ABS)

Roles or Functions of Geosynthetics

Separator

Reinforcement

Drainage

Filter

Energy absorber

Container

Barrier

Geosynthetic Global Offer

Types of Geosynthetics

Geotextiles (GT)

Geogrids (GG)

Geonets (GN)

Geomembranes (GM)

Geosynthetic clay liners (GCL)

Geocomposites (GC)

Geo others Geopipe, Geofoam, Geocells, Geomesh

Geotextiles (GT)

Geotextiles (GT)

Flexible, textile-like fabrics

Majority are made from polypropylene fibers

Woven (slit film, monofilament or multifilament)

Nonwoven (needle punched or heat/chemical bonded)

Characterised by an open and porous structure(with controlled permeability)

Mechanical and Hydraulic properties vary widely

Very versatile in their primary function(except as liquid barrier)

Geogrids (GG)

Geogrids (GG)

stiff or flexible polymer grid-like sheets

structure allows for soil “strike-through”

bidirectional – equal strength in both directions

unidirectional – main strength in machine direction

focuses entirely on reinforcement applications, e.g.,walls, steep slopes, base and foundation reinforcement

Geonets (GN)

Geonets (GN)

all are made from high density polyethylene

results in parallel sets of ribs as a integral unit

biplanar – flow is equal in all directions

triplanar – flow much greater in machine direction

function is always in-plane drainage

surfaces must be covered; usually with GTs

Geomembranes (GM)

Geomembranes (GM)

impermeable sheets (10-11 to 10-13 cm/s)

function is always containment

represents a barrier to liquids and gases

many types: HDPE, LLDPE, fPP, PVC, EPDM, etc.

manufactured rolls are field seamed

new applications in hydraulics and private development

Geosynthetic Clay Liners (GCL)

function is always containment

common product is bentonite between 2-GTs

internally reinforced by needle punched or stitching

bentonite product bonded to GM is also available

many other variations exist

competitive with compacted clay liners (CCLs)

beneath a GM; one has a composite liner

Geosynthetic Clay Liners (GCL)

Geopipe (GP)

GEOPIPE

Geopipe (GP)

its really buried plastic pipe!

function is always drainage

HDPE and PVC most common

can be smooth walled or corrugated

corrugated HDPE growth is enormous

Geofoam (GF)

GEOFOAM

Geofoam (GF)

lightweight fill on soft or sensitive soils

relieves lateral pressure on walls

also used for insulation of frost-sensitive soils

Geocomposites (GC)

Geocomposites (GC)

hybrid systems of any or all

array of available products

GT/GM; GT/GG; GT/GN; etc.

considerable ongoing innovation

primary function depends on final product

Function vs. Geosynthetic Type

Type of Geosynthetic

Separation Reinforcement Filtration Drainage Containment

geotextile

geogrid

geonet

geomembrane

geosynthetic clay liner

geopipe

geofoam

geocomposite

Properties of Geosynthetics -Parameters

Physical

Chemical

Mechanical

Hydraulic

Endurance

Degradation

Physical

Thickness

Specific Gravity

Mass per unit area

Porosity

Percent open area

Apparent opening size

Parameters . . . .

Chemical

Polymer type

Filler material

Carbon black percentage

Plasticizers and additives

Manufacturing process

Parameters . . . .

Mechanical Tensile strength

Compressibility

Elongation

Tear/impact/puncture resistance

Burst strength

Seam strength

Fatigue resistance

Interface friction with soil

Anchorage in soil

Parameters . . . .

Hydraulic

Permittivity (cross plane permeability)

Transmissivity (in plane permeability)

Clogging potential

Parameters . . . .

Endurance

Installation damage potential

Tear/impact/puncture resistance

Abrasion resistance

creep

Parameters . . . .

Degradation

Resistance against

Ultraviolet radiation

Temperature

Oxidation

Aging

Chemical and Biological reactions

Parameters . . . .

Properties of GeosyntheticsRange of Values

TypeThickness

(mm)

Mass per unit area

(gsm)

Tensile strength

(kN/m)

Elongation

(%)

Apparent opening size

(mm)

Non-Woven Geotextile

0.25 – 7.5 100 – 2000 5 – 100 20 – 100 0.02 – 0.6

Woven Geotextile

0.25 – 3.0 100 – 1500 20 – 400 10 – 50 0.05 – 2.0

Geomebranes 0.25 – 3.0 250 – 3000 10 – 50 50 – 200 ~ 0

Geogrids 5.0 – 15.0 200 – 1500 10 – 200 5 – 25 10 – 100

Geonets 3.0 – 10.0 100 – 1000 – – 5 – 15

Separation

High tensile strength (20 – 400 kN/m)

Allow flow of water but no mixing of soil

High burst strength

High tear/impact/puncture resistance

Geotextiles (usually woven)

Functional requirements

Filtration

Cross-plane permeability higher than base soil

(10e-5 to 1 m/s)

Pore size small enough to enable retention of fines

(95% pore size – 0.02 to 2.0 mm)

Low clogging potential

Geotextiles (usually non-woven)

Functional requirements . . . .

Drainage

Requirements of filtration

High in-plane permeability

Geotextiles (thick non-woven)

Geonets sandwiched b/w geotextiles

(Geocomposite sheet drain)

Functional requirements . . . .

Reinforcement High tensile strength

Low elongation (high stiffness) (5 to 25%)

High shearing resistance along soil reinforcement interface

Geotextiles (low elongation)

Geogrids

Functional requirements . . . .

Barrier

High imperviousness (10e-12 to 10e-15 m/s)

Leakproof welding along seams

No slippage when laid along sloping ground

Geomebranes

Functional requirements . . . .