During the past half century, using various artificial materials under the title of geosynthetic has had an intensive progress in civil engineering projects. These materials are made of rubber and plastic materials and they are produced with various shapes and properties depending on their application and expected performance. Splitting, filtration, protection, drainage, arming and insulation from moisture are some of the main geosynthetic applications. Geosynthetics are widely used in many projects such as: dams, roads, retaining wall, buildings, soil improvement and many projects related to soil. Geosynthetics divide into a few major groups including geotextile, geogrid, geomembrane, geonet, geocomposite, GCL and geocel.
Geotextiles are usually produced in the form of woven or nonwoven fabrics. Woven geotextiles are made from mashing the vertical and horizontal strings that the final result of this, is the emergence of a resistant layer and somethings like fabric. Woven and nonwoven geotextiles are made of strings and fibers are generally polymer and they are consistent of polypropylene, polyester, polyethylene and polyamid. There's a small group of geotextiles which are consist of fiber and they are mainly used in the field of erosion control. The geotextiles applications are often for soil reinforcement, separating layers, soil drainage, increasing the bearing capacity of asphalt and soil, increasing the useful life of asphalt, construction protection of coastal and marine, homogenous subsidence in marine structures such as breakwaters eroding lands protection, protection of the upper layer on the railway, increasing the bearing capacity of subgrade of road and railway, protection of geomembrane layer and many others.
Geogrids are produced from materials such as polyethylene, polyester, fiberglass with different covers. Geogrids are grid mesh which are horizontal screens to keep the walls strong and they are used for soil reinforcement. Geogrid has more locking property compared with geotextile it means that geogrid involves with soil particles and it gives high bending resistance to its platform. The application of this product is mostly on retaining walls and road construction.
Geomembranes are often a sheet of polyethylene or PVC with insulation property of various surfaces without the need of special foundations. Using this product makes the surface impervious toward any kinds of fluid (for example; water, chemicals and petroleum). These products are often used for: sealing, artificial lakes construction, fish farms and industrial pools, waste water lagoons and water and waste water pipe liners. Geomembrane can be installed singly or with covers such as concrete slabs or gravel materials. Among other applications of this product, using for improving the quality of old dam, isolation, prevent subsidence in the floor of tanks, marine structures, etc. Geotextile is usually placed on and under the geomembrane to protect it against perforation, it also reinforces the strength of load bearing structure and geomembrane.
Geonets are produced from continuous injection of polymeric tapes with the exact angle relative to each other. They are usually made of polyethylene. Geonets with different pore sizes are available and depending on the size of soil particles are selected to create drainage possibility without displacement of soil particles. Thus, the main function of geonet is drainage geonets application is mainly to prevent slope erosion and proper drainage. Because of the low price of geotextiles, the application of geonets is limited.
Geocomposites are combination of different sheets such as; geotextile + geonet, geotextile + geogrid, geotextile + geocel, geomembrane + geotextile and in many cases used as filter-drain.
GCL is a type of geocomposite composed of geosynthetic sheets with clay interlayers (bentonite) and they are used for preventing water leakage and sealing. The common type of GCL is consist of a bentonite layer between two sheets of geotextile or between a layer of geotextile and geomembrane. Particular advantage of GCL is its self-healing and fusion property.
Geocels are formation of a three dimensional network of nonwoven polyesters which are used for preventing erosion and slopes erosion control.