Geocomposite

Geosynthetics are manufactured synthetic materials (i.e., made from polymers or hydrocarbon chains) that are used for a wide range of engineering applications. Seven categories of geosynthetic materials are manufactured: geocomposites, geogrids, geomembranes, geonets, geopipes, geotextiles, and geosynthetic clay liners. The geocomposite consists of a combination of one or more geosynthetics, specifically a geogrid, a geotextile, a geomembrane, and/or a geonet, with another material. Geotextiles are used primarily for applications requiring separation, filtration, reinforcement, and drainage. Geogrids are used as reinforcement to improve the strength of soil or other materials. Geonets are relatively thin, planar geosynthetics used for drainage applications, whereas geopipes are buried plastic pipes used for drainage. Geomembranes and geosynthetic clay liners are thin (≤ 10 mm), relatively impervious geosynthetics that are used as barriers in containment applications for waste disposal and in situ remediation. Geosynthetics have gained widespread use only since about 1990, but their use in geoenvironmental engineering applications involving liquid and waste containment has grown substantially in the last decade. A detailed description of the properties, characteristics, and uses of each of these types of geosynthetic can be found in our wibsite.

❖Geotextile-geonet composites

When a geotextile is used on one or both sides of a geonet, the separation and filtration functions are always satisfied, but the drainage function is vastly improved in comparison to geotextiles by themselves. Such geocomposites are regularly used in intercepting and conveying leachate in landfill liner and cover systems and for conducting vapor or water beneath pond liners of various types. These drainage geocomposites also make effective drains to intercept water in a capillary zone where frost heave or salt migration is a problem.[citation needed] In all cases, the liquid enters through the geotextile and then travels horizontally within the geonet to a suitable exit.

❖Multi-linear drainage composites

A manufactured product composed of a series of parallel single drainage conduits (like perforated mini-pipes) regularly spaced across the width of the product and sandwiched between two or more geosynthetics (more often geotextiles). They are used for liquid drainage or gas collection while providing a separation and filtration function. Such multi-linear drainage composites are not susceptible to creep in compression or geotextile intrusion when confined in the soil, which means that they maintain their flow capacity over time, even under heavy loads.These drainage geocomposites are regularly used in landfill applications for leachate collection layers and cover systems, and in buildings for sub-slab depressurization systems to collect toxic gases (Radon, VOCs, etc.) and prevent their migration into the building.

❖Geotextile-geomembrane composites

Geotextiles can be laminated on one or both sides of a geomembrane for a number of purposes. The geotextiles provide increased resistance to puncture, tear propagation, and friction related to sliding, as well as providing tensile strength in and of themselves. Geotextiles are of heavy and are of the nonwoven, needle-punched variety. In such cases the geotextile component acts as a drainage medium, since it can conduct water, leachate or gases away from direct contact with the geomembrane.

❖Geomembrane-geogrid composites

Since some types of geomembranes and geogrids can be made from the same material (e.g., high-density polyethylene), they can be bonded together to form an impervious membrane barrier with enhanced strength and friction capabilities.

❖Geotextile-geogrid composites

A needle-punched nonwoven geotextile bonded to a geogrid provides in-plane drainage while the geogrid provides tensile reinforcement. Such geotextile-geogrid composites are used for internal drainage of low-permeability backfill soils for reinforced walls and slopes. The synergistic properties of each component enhance the characteristics of the final product.

❖Geotextile-polymer core composites

A core in the form of a quasi-rigid plastic sheet, it can be extruded or deformed in such a way as to allow very large quantities of liquid to flow within its structure; it thus acts as a drainage core. The core must be protected by a geotextile, acting as a filter and separator, on one or both sides. Various systems are available, each focused on a particular application.