Geomembranes and Geotextiles for Earth Reinforcement

GEOMEMBRANES AND GEOTEXTILES FOR EARTH REINFORCEMENT

Geomembranes are impermeable membranes used widely as cut-offs and liners. These are used mostly as canal and pond liners; however, one of the largest current applications is to the containment of hazardous or municipal wastes and their leachates. In many of these applications geomembranes are employed with geotextile or mesh underliners, to reinforce or protect the more flexible geomembrane whilst also acting as an escape route for gases and leachates generated in certain wastes. Geofabrics are also called geosynthesis or geotextiles. These are synthetic fabrics which are sufficiently durable to last a good length of time in soil environment used in geotechnical engineering. Some geofabrics are polyester, nylon, polyethylene and geotechnical engineering. The fabric may be woven, knitted or punched. They are used for the following functions:

❖ Drainage paths for water for soil consolidation

❖ Separation of different types of soil materials

❖ Soil reinforcement in reinforced earth construction

❖ Filtration of water from soil.

GEOTEXTILES FOR EARTH REINFORCEMENT

Geotextiles are permeable fabrics which, when used in association with soil, have the ability to separate, filter, reinforce, protect or drain. As the use of geotextile fabrics has expanded there has been the introduction of geotextile composites and the development of products such as geogrids and meshes. Overall these materials are referred to as geotextiles and related products. These are ideal for use in soil as they do not deteriorate by corrosion in the presence of chemicals. They last for a long time when not exposed to direct sunlight and are also not affected by water. They are extensively used for Mechanically Stabilized Earth (MSE) / Reinforced Earth Construction. and eyewlin

CLASSIFICATION

❖ Geotextiles: These materials consist of either woven or non-woven fabrics and are generally used for separation, drainage, filtration and reinforcement. The strongest of these are woven fabrics, then the resin bonded, melt bonded and finally the needle punched fabrics.

❖ Geogrids: They have large openings and are made of materials with high tensile strength, low elongation and dimensional stability. They are made from plain polymer sheets by punching holes in it followed by two stretching operations so that a grid is formed. They can be designed to have different strength or same strength in two directions. They are mainly used for soil reinforcement or for separation of materials or for improving bearing capacity of soil

❖ Geomembranes: These materials are available in wide range of permeability. Continuous geomembrane barriers of sufficiently low permeability can be used to control fluid migration in geotechnical engineering while those of high permeability are used for drainage.

❖ Linear strips for soil reinforcement: Polymer fibres are made into strips which can be used for reinforced earth in retaining walls. Glass- reinforced plastics are also considered as suitable for soil reinforcement.

 USES OF GEOTEXTILES

❖ As the embankments for flyovers in cities should occupy as little width as possible, the use of geotextiles as soil reinforcement for these embankments comes in very handy.

❖ Much steeper slopes than normally admissible with earth only can be provided by using soil reinforcement in the embankment.

❖As soil reinforcement for retaining walls and stability of slopes. For improving the bearing capacity of foundations.

❖As a filtration medium for drainage. In many situations, when used for drainage and separation, it also acts as a filter.

❖ Many new railway embankments for Indian Railways has been carried out by using plastic geotextile drains instead of old fashioned sand or wick drains. It is used as under railway track, to separate the ballast from sub grade, thus decreasing penetration of ballast into the weak sub grade.

❖ Geotextiles are used as drainage wicks to assist drainage and consolidation of clayey deposits. The modern readymade plastic geotextile drain consists of a plastic drain core and a geotextile jacket covering the plastic core pipe. They are efficient for soil drainage to assist in preloading of foundations.