Geotextiles are used with foundations, soils, rock, earth, or other geotechnical material as an integral part of a manufactured project, structure, or system. These textile products are made of synthetic fibers or yarns and constructed into woven or nonwoven fabrics that weigh from 3 to 30 oz/yd2 (100 to 1000g/m2). Geotextiles are more commonly known by other names, for example, filter fabrics, civil engineering fabrics, support membranes, and erosion control cloth.
Permeable geotextiles perform three basic functions in earth structures: separation, reinforcement, and filtration. Such geotextiles can thus be adapted to numerous applications in earthwork construction. The major end-use categories are stabilization (for roads, parking lots, embankments, and other structures built over soft ground); drainage (of subgrades, foundations, embankments, dams, or any earth structure requiring seepage control); erosion control (for shoreline, riverbanks, steep embankments, or other earth slopes to protect against the erosive force of moving water); and sedimentation control (for containment of sediment runoff from unvegetated earth slopes).
A geomembrane is any impermeable membrane used with soils, rock, earth, or other geotechnical material in order to block the migration of fluids. These membranes are usually made of synthetic polymers in sheets ranging from 0.01 to 0.14 in. (0.25 to 3.5 mm) thick. Geomembranes are also known as flexible membrane liners, synthetic liners, liners, or polymeric membranes.
Early liners included clay, bentonite, cement-stabilized sand, and asphalt. Modern geomembranes are commonly made of medium-density polyethylenes that are very nearly high-density polyethylenes (HDPE), several types of polyvinyl chloride (PVC), chlorosulfonated polyethylene (a synthetic rubber), ethylene propylene diene monomer (EPDM), and several other materials. Some geomembranes require reinforcement with an internal fabric scrim for added strength, or plasticization with low-molecular-weight additives for greater flexibility. See also Polymer.
Geomembranes are able to contain fluids, thus preventing migration of contaminants or valuable fluid constituents. Since they prevent the dispersal of materials into surrounding regions, geomembranes are often used in conjunction with soil liners, permeable geotextiles, fluid drainage media, and other geotechnical support materials. The major application of geomembranes has been containment of hazardous wastes and prevention of pollution in landfill and surface impoundment construction. They are also used to a large extent in mining to contain chemical leaching solutions and the precious metals leached out of ore, in aquaculture ponds for improved health of aquatic life and improved harvesting procedures, in decorative pond construction, in water and chemical storage-tank repair and spill containment, in agriculture operations, in canal construction and repair, and in construction of floating covers for odor control, evaporation control, or wastewater treatment through anaerobic digestion. See also Hazardous waste.