Geotextile
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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 geosynthetics and each configuration—geonets, geogrids and others—can yield certain benefits in geotechnical and environmental engineering design. These products have a wide range of applications and are currently used to advantage in many civil engineering applications including roads, airfields, railroads, embankments, retaining structures, reservoirs, canals, dams, bank protection and coastal engineering.
[edit] Geomembranes
Geomembranes are impermeable membranes used widely as cut-offs and liners. Until recent years, geomembranes were used mostly as canal and pond liners. One of the largest current applications is the containment of hazardous and municipal wastes and their leachates. In many of these applications geomembranes are employed with geotextile or mesh underliners which reinforce or protect the more flexible geomembrane whilst acting as an escape route for gases and leachates generated in some wastes.
Geomembranes are made of various materials including low density polyethylene (LDPE), high density polyethylene (HDPE), polyvinyl chloride (PVC) and polypropylene (PP). Another type of geomembrane is bituminous geomembrane, which is a layered product of glass and bitumem-impregnated non-woven geotextile.
Each type of geomembrane material has different characteristics which affect installation procedures, lifespan and performance. For example, PVC geomembranes are very flexible and as a result can conform to uneven surfaces without being punctured. Polypropylene is susceptible to UV radiation and should not be used in where it will be exposed to sunlight or it will become brittle.
[edit] Geogrids
Geogrids are meshes typically made of a regular pattern of tensile elements usually made of a fairly rigid type of plastic. These are used to strengthen fill materials in geotechnical applications. They provide increased shear strength at soil strata interfaces. Their tensile strength can prevent or decrease the degree of differential settlement in by transmitting load over a larger area, diminishing the vertical stress—and subsequent compression—in the soil.
