GEOSYNTHETICS ENGINEERING: IN THEORY AND PRACTICE Prof. J. N. Mandal Department of Civil Engineering, IIT Bombay, Powai, Mumbai 400076, India. Tel.022-25767328 email: cejnm@civil.iitb.ac.in
Module - 2 LECTURE - 6 AN OVERVIEW OF GEOSYNTHETICS
OUTLINE Introduction Categories of geosynthetics Geosynthetics scope and definitions Raw materials and machineries Composition of geosynthetics Types of geosynthetics and functions Geosynthetic functional applications Multiple functions of geosynthetics Design of geosynthetic Sustainability using geosynthetics
INTRODUCTION In the past four decades, extensive research has been carried out on geosynthetics around the world. It is required to attain good design, good research and at the same time good material and good construction technique to overcome the educational and technical challenges. The dynamic and rapid growth of geosynthetic is exciting, emerging and vibrant in the field of civil engineering. Today, more than twenty billion square meters of geosynthetics have exclusively been used in several million projects (Giroud, 2012).
The jute geotextile was successfully used on Strand road in Kolkata in 1934 by Bengal PWD and subsequently in Myanmar during 2 nd world war. The jute geotextile had also been used for erosion control in 1980. The revolutionary development of geosynthetics has been started in the early 1970s in the field of construction industry. Geosynthetics provide proper solution to design and construction problems in spite of climatic, geographic or technological differences. The uniqueness of geosynthetics is that they ensure multifunctional performances and simple to use and provide great economical potential advantages.
Geosynthetics classifications (After Rankilor 1981) Textiles Webbings polymers Synthetic Natural Synthetic Natural Cotton, jute, reeds, grass Steel, polymers Palm leaf, wood, bamboo Impermeabl e Geomembrane Permeable Closed mesh Combination products Open mesh Geogrids Strips Reinforced earth Geotextiles Non-oven knitted woven Combination products Needle-punched (thick) Needle-punched (thin) Monofilament Silt film Multifilament Unmodified Reinforced Spun bonded Melded stabilized e. g. calendared Non stabilized stabilized Non stabilized e. g. calendared Melded Reinforced
GEOSYNTHETICS SCOPE AND DEFINITIONS What are Geosynthetics? Geosynthetic is a product made of polymeric/natural material used with soil and rock, or any other related geotechnical engineering materials for the construction of Civil Engineering structure, or system. Why would we want to use them? Sustainable development and environment protection can go hand - and hand. It reduces maintenance cost and increases life. It saves substantial cost over alternative solutions. The quality can be controlled as manufactured in a factory It is widely available. It has generic specifications and easy to install.
Optimum technical properties of Geosynthetics: It has excellent stress-strain behavior It has good flexibility It has excellent filtration characteristics It has high water permeability It can provides excellent mechanical protection It can be welded together It does not form by-products It is highly resistant to chemical and biological attack, and It is chemically ultraviolet stabilized
When can we use them? Low bearing capacity of the soil Excessive Settlement of soil Soft soil treatment (Reclamation of Land) Limited space for construction Land Saving To control and protect the environment Swelling soil Faster Construction Saving in time Saving in cost Sustainable environmental safety To maintain quality assurance / quality control (QA/QC)
Where can we use them? Geotechnical Engineering Transportation Engineering Geo environmental Engineering Coastal/Hydraulics/Water Resources Engineering Mining Engineering Agricultural Engineering Earth quake Engineering Bio Engineering
How can we use them? We can use geosynthetics based on their major functions and specifications. There are six major functions: Separation Filtration Drainage Reinforcement Protection, and Sealing
Who produce Geosynthetics? Around the world there are many manufacturing companies that produce comprehensive range of Geosynthetics and any other related products used in Civil engineering and construction systems. CATEGORIES OF GEOSYNTHETICS Geotextiles (Knitted, Nonwoven, Woven) Geogrid (Bonded, Extruded, Knitted, Woven) Geomembrane (Bituminous, Elastomeric, Plastomeric) Geonets Geosynthetics Clay Liner Geocomposite drains (PVD, Geonets or Geospacers) Geopipes
Geostrips Geospacers Geocomposite Glassgrid Geoarmour Geoblanket Geofoam Geomats Geocombs Geotextile container Geotextile bags Geotextile tubes Geo coir Geo jute Bamboo Geocell / Geoweb Gabion Fiber Hybrid geosynthetics Electro kinetic geosynthetics Smart Geosynthetics Geo straw
RAW MATERIALS USED FOR THE PRODUCTION OF VARIOUS TYPES OF GEOSYNTHETICS Polypropylene (PP) Polyethylene (PE) Polyamide/ Nylon (PA) High density polyethylene (HDPE) Low density polyethylene (LDPE) Linear low density polyethylene (LLDPE) Medium density polyethylene (MDPE) Very low density polyethylene (VLDPE) Chlorinated polyethylene (CPE) Chloro-sulphonated polyethylene (CSPE)
Polystyrene (PS) Polyester or polyethylene terephthalate (PET) Polyvinyl chloride (PVC) Chlorinated Polyethylene (CPE) Ethylene Propylene diene terpolymer (EPDM) Expanded polystyrene (EPS) Geo Jute (GJ) Geo Coir (GC) Bamboo (B) Sisal (S) Straw (SW)
RAW MATERIALS USED FOR THE PRODUCTION OF VARIOUS TYPES OF GEOSYNTHETICS Raw materials PP, PET, PE, PA, GJ, GC, S, SW PET, PP, HDPE, GC, B, S PVC, PP, HDPE, LLDPE, VLDPE, CPE, CSPE, GJ HDPE, MDPE,GJ, GC, S, SW HDPE, PP, PVC EPS Geosynthetics Geotextiles Geogrids Geomembranes Geonets Geopipes Geofoams
COMPOSITION OF GEOSYNTHETICS Geosynthetics are made of different types of fibers or yarns: Monofilament Silt-film monofilament Multifilament Silt-film multifilament Staple fibers Staple yarn Stable fibers Filaments Silt films
Woven geosynthetics and knitted geosynthetics can be made of yarns as follows: A monofilament yarn A spun yarn A multifilament yarn A fabricated yarn and A slit film yarn The nonwoven geosynthetics can be made of stable fibers or filaments. The arrangement of fibers is random and bonded together with the following systems: Mechanical bonding Chemical bonding Heat/ Thermal bonding Resin bonding Spray bonding Spun bonding Stitch bonding
Manufacturing of Geogrid Strata India (Courtesy to Mr. N. Dalmia)
Tensar International (1996, 1997 and 1999)
DIFFERENT TYPES OF GEOSYNTHETICS GEOTEXTILES (GT) Nonwoven geotextile Woven geotextile Nonwoven geotextiles supplied by manufacturers Woven geotextiles supplied by manufacturers
Nonwoven Geotextiles: Mechanically bonded nonwoven Thermally bonded non-woven
Woven Geotextiles: Monofilament-on-multifilament Multifilament-on-multifilament
GEOGRIDS (GG) Woven geogrids: Yarns are weaved perpendicular to each other Bonded geogrids: Two or more sets of strands are bonded together perpendicular to each other Knitted geogrids: Yarns are knitted together perpendicular to each other Extruded geogrids: Geogrid polymer is made of sheet form
GLASS GRIDS
GEONETS
GEOMEMBRANE Geomembranes are made of relatively impermeable thin continuous flexible plastic sheets or rubber materials. It has smooth or rough surfaces either on one or both sides. Geomembranes are of two types: Calendared geomembranes are polyvinyl chloride (PVC), polyethylene (PE) and ethylene interpolymer alloy (EIA). Extruded geomembranes are high-density polyethylene (HDPE), Low-density polyethylene (LDPE), very flexible polyethylene (VFPE) and polypropylene (PP).
Different types of geomembranes supplied by the manufacturers
GEOCOMOPITES (GC)
GEOCOMPOSITE EROSION CONTROL MATS Geocomposite Erosion control mat supplied by manufacturers
GEOSPACERS / GEOSTRIPS
GEOSYNTHETIC CLAY LINERS (GCL)
GEOTEXTILE TUBES Schematic view of geotextile tube GEOPIPES
GEOFOAM Geofoam blocks or slabs are made of expanded polystyrene (EPS) or extruded polystyrene (XPS). It is a very lightweight material with high void content and its density is very low compared to the soil.
GEOCELL/ GEOWEB
GEOTEXTILE CONTAINERS GEOMATTRESS/ GEOTEXTILE BAG
NATURAL GEOTEXTILE Geojutes supplied by manufacturers Geocoirs supplied by manufacturers
GABIONS FIBERS
ELECTROKINETICS GEOSYNTHETICS: These are basically quick drainage materials. These are electrically conductive geosynthetics. It performs soil consolidation by electro-osmosis process. GEOBLANKET: It is made of synthetic or natural biodegradable permeable materials. It is used for temporary erosion control with vegetations. GEOMAT: It is a three dimensional permeable material. It is made of bonded filaments. It can be used for permanent erosion control problems. The roots of grass and small plants act as reinforcement for vegetation.
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Prof. J. N. Mandal Department of civil engineering, IIT Bombay, Powai, Mumbai 400076, India. Tel.022-25767328 email: cejnm@civil.iitb.ac.in