Geocomposite

Materials to improve technical properties of soil or geotechnical structure

[[File:Geocomposite drain installation. jpg|thumb|upright=1.1|Installation of a geocomposite drain. These drainage geocomposites also make effective drains to intercept water in a capillary zone where frost heave or salt migration is a problem. In all cases, the liquid enters through the geotextile and then travels horizontally within the geonet to a suitable exit.

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.

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. The second type is in the form of drainage panels, the rigid polymer core being nubbed, columned, dimpled or a three dimensional net. With a geotextile on one side it makes an effective drain on the backfilled side of retaining walls, basement walls and plaza decks. The cores are sometimes vacuum formed dimples or stiff 3 D meshes. As with wick drains, the geotextile is the filter/separator and the thick polymer core is the drain. Many systems of this type are available, the latest addition having a thin pliable geomembrane on the side facing the wall and functioning as a vapor barrier. The third type within this area of drainage geocomposites is the category of prefabricated edge drains. These materials, typically 500 mm high by 20 to 30 mm wide are placed adjacent to a highway pavement, airfield pavement, or railroad right of way, for lateral drainage out of and away from the pavement section. The systems are cost effective and can be installed quickly.