Geosynthetics. Nanjundaswamy P. Dept. of Civil Engineering S J C E, Mysore

Transcription

1 Geosynthetics Nanjundaswamy P. Dept. of Civil Engineering S J C E, Mysore

2 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

3 Polymer - Types & Materials Polypropylene(PP) Polyethylene (HDPE, LDPE, LLDPE) Polystyrene (PS) Polyvinyl Chloride (PVC) Polyamide (PA) eg. Nylon Polyester Acrylonitrile Butadiene Styrene (ABS)

4 Roles or Functions of Geosynthetics Separator Reinforcement Drainage Filter Energy absorber Container Barrier

5 Geosynthetic Global Offer

6 Types of Geosynthetics Geotextiles (GT) Geogrids (GG) Geonets (GN) Geomembranes (GM) Geosynthetic clay liners (GCL) Geocomposites (GC) Geo others Geopipe, Geofoam, Geocells, Geomesh

7 Geotextiles (GT)

8 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)

9 Geogrids (GG)

10 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

11 Geonets (GN)

12 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

13 Geomembranes (GM)

14 Geomembranes (GM) impermeable sheets (10-11 to 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

15 Geosynthetic Clay Liners (GCL)

16 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

17 Geopipe (GP) GEOPIPE

18 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

19 Geofoam (GF) GEOFOAM

20 Geofoam (GF) lightweight fill on soft or sensitive soils relieves lateral pressure on walls also used for insulation of frost-sensitive soils

21 Geocomposites (GC)

22 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

23 Function vs. Geosynthetic Type Type of Geosynthetic Separation Reinforcement Filtration Drainage Containment geotextile geogrid geonet geomembrane geosynthetic clay liner geopipe geofoam geocomposite

24 Properties of Geosynthetics - Parameters Physical Chemical Mechanical Hydraulic Endurance Degradation

25 Parameters.... Physical Thickness Specific Gravity Mass per unit area Porosity Percent open area Apparent opening size

26 Parameters.... Chemical Polymer type Filler material Carbon black percentage Plasticizers and additives Manufacturing process

27 Parameters.... Mechanical Tensile strength Compressibility Elongation Tear/impact/puncture resistance Burst strength Seam strength Fatigue resistance Interface friction with soil Anchorage in soil

28 Parameters.... Hydraulic Permittivity (cross plane permeability) Transmissivity (in plane permeability) Clogging potential

29 Parameters.... Endurance Installation damage potential Tear/impact/puncture resistance Abrasion resistance creep

30 Parameters.... Degradation Resistance against Ultraviolet radiation Temperature Oxidation Aging Chemical and Biological reactions

31 Properties of Geosynthetics Range of Values Type Thickness (mm) Mass per unit area (gsm) Tensile strength (kn/m) Elongation (%) Apparent opening size (mm) Non-Woven Geotextile Woven Geotextile Geomebranes ~ 0 Geogrids Geonets

32 Functional requirements Separation High tensile strength ( kn/m) Allow flow of water but no mixing of soil High burst strength High tear/impact/puncture resistance Geotextiles (usually woven)

33 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)

34 Functional requirements.... Drainage Requirements of filtration High in-plane permeability Geotextiles (thick non-woven) Geonets sandwiched b/w geotextiles (Geocomposite sheet drain)

35 Functional requirements.... Reinforcement High tensile strength Low elongation (high stiffness) (5 to 25%) High shearing resistance along soil reinforcement interface Geotextiles (low elongation) Geogrids

36 Functional requirements.... Barrier High imperviousness (10e-12 to 10e-15 m/s) Leakproof welding along seams No slippage when laid along sloping ground Geomebranes

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