A geocomposite consists of a combination of geotextile and geogrid; or geogrid and gromembrane; or geotextile, geogrid, and geomembrane; or any one of these three materials with another material (e.g., deformed plastic sheets, steel cables, or steel anchors). This exciting area brings out the best creative efforts of the engineer, manufacturer, and contractor. The application areas are numerous and growing steadily. The major functions encompass the entire range of functions listed for geosynthetics discussed previously : separation, reinforcement, filtration, drainage, and liquid barrier.

Geotextile - Geonet Composites

When one uses a geotextile over or under a geonet, or makes a geotextile-geonet-geotextile sandwich, the separation and filtration functions are always satisfied, but the drainage function is vastly improved over geotextiles by themselves. Placed horizontally, they make excellent dranis to upwardly moving water in a capillary zone where frost heave or salt migration is a problem. When the water enters the sandwich it travels horizontally within the geonet and away from where damage can occur. Such geocomposites have also been used in intercepting and conveying of leachate in landfills and for conducting vapor or water beneath pond liners of various types.

Geotextile - Geomembrane Composites

Geotextiles are laminated on one or both sides of a geomembrane for a number of puposes. In the reinforcement area, the geotextiles provids increased resistance to puncture, tear propagation, and friction related to sliding, as well as providing tensile strength in and of themselves. Quite often, however, the geotextiles are of the nonwoven, needle-punched variety and are of relatively heavy weight. In such cases they act as drainage media, since their in-plane transmissivity feature can conduct water or leachate away from direct contact with the geomembrane.

Geomembrane - Geogrid Composites

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

Geotextile - Geogrid Composites

Those geotextiles with low modulus, low strength and / or high elongation at failure can be greatly improved by forming a composite material with a geogrid, or even with a woven fabric scrim. The synergistic properties of each componenet usually enhances the final product.

Geotextile / Polymer - Core Composites

When one takes 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 water to flow within ts structure. It thus acts like a drainage core. The core is protected by a geotextile, acting as a filter, on one or both sides. Many systems are available. Strip, or wick, dranis fall into this group and it might eventually form a category in its own right, the word "geospacer" has been suggested. Here the polymer core is often fluted for ease of conducting water and formed about 4 in. (100 mm) wide with a geotextile stocking around it. The emergence of geotextile polymer-core composites has all but eliminated traditional sand drains as a rapid means of consolidating fine-grained saturated soils.
In the form of panels, the rigid polymer core can be nubbed, columned or dimpled and with a geotextile on one side makes an excellent drain on the backfilled side of retaining walls, basement walls and plaza decks. These cores are often vacuum formed. As with strip drains, the geotextile is the filter and the deformed polymer core is the drain. Many systems of this type are available, the latest addition having a thin pliable geomembrane on the facing the wall and functioning as a vapor barrier.
Lastly, within this area of drainage geocomposites comes the category of prefabricated edge drains. These materials, typically 18 in. (45 cm) are placed adjacent to a highway pavement or rail road right-of-way for lateral drainage out of, and away from, the pavement section. The systems are incredibly rapid in their installation and extremely cost effective.

Geosynthetic - Soil Composites

As typified by the geosynthetic clay liners, many other variations of geosynthetic products and soil can be developed.
For example, geocells are rigid polymer strips and geotextiles have been cleverly arranged vertically in a boxlike fashion, placed horizontally (standing upright) and filled with soil. Thus the material forms a cellular structure and acting with the contained soil, makes an impressively strong and stable mattress. Sizable earth embankments have been built on such structures with the possibility of supporting structures over weak soils weak soils in the near future (i.e., an inexpensive mat foundation).
Another variation is to use continuous polymer fibers and sand to form a steep slope with excellent strength properties. The fibers give the composite material a very pronounced apparent cohesion.

Other Geocomposites

By weaving steel strands within a geotextile matrix, incredible composite material strength can result. Used as a substrate, extrmely large loads can be sustained. A measurable increase in bearing capacity for the support of buildings is alos possible.
Open-graded styrofoam beads have been sandwiched between geotextile (as filters) and geomembranes (as vapor barriers) for drainage materials behind basement walls and earth-sheltered homes. Here the styrofoam acts as teh drain but has the added advantage of acting as a heat insulator.
Geotextiles with prefabricated holes for the insertion of steel rod anchors have been used to stabilize slopes and as in-situ compaction and consolidation systems. The rods act as anchors, stressing the geotextile against the soil, which is put into compression. The geotextile thus acts dually as a tensile stressing mechansim and as a filter allowing the pore water to escape while retaining the individual soil particles.
Added to this list are short fibers, grids, and nets to be placed in concrete or bitumen to form a high impact composite material, etc.

Major Applications of Geocomposite

  1. Geomembrane Protection
  2. Gas Venting
  3. Drainage


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