Types of Geosynthetic Materials

Geosynthetic Materials

Geotextiles – Textiles in the traditional sense, they consist of synthetic fibers so that biodegradation is not a problem.  They make up one of the two largest groups of geosynthetics.  These synthetic fibers are made into a flexible fabric by standard weaving machinery or are matted together in a random, or nonwoven, manner.  The fabric is porous to water flow across its manufactured plane and within its plane.  There are at least 80 specific applications for geotextiles, but the fabric always performs at least one of five discrete functions: separation, reinforcement, filtration, drainage, or barrier to moisture.

Geomembranes – These are the other largest group of geosynthetics.  In sheer sales volume, they are probably larger than geotextiles because their growth has been stimulated by government regulations enacted in 1982.  The materials themselves are impervious thin sheets of rubber or plastic material used primarily for linings and covers of liquid- or solid-storage facilities.  Thus, the primary function is always as a liquid or vapor barrier.  The range of applications, however, is very great, and at least 30 applications in civil engineering have been developed.

Geogrids – Plastics formed into very open, gridlike configurations, geogrids have at least 25 applications, but they function almost exclusively as reinforcement materials. They represent a rapidly growing segment within the geosynthetics family, says Drexel University Professor Grace Hsuan.

Geonets – Also called “geospacers,” these products are usually formed by a continuous extrusion of parallel sets of polymeric ribs at acute angles to one another.  When the ribs are opened, relatively large apertures are formed into a netlike configuration.  Their design function is completely within the drainage area, where they have been used to convey fluids of all types, explains Hsuan.

Geosynthetic Clay Liners – Rolls of thinly layered bentonite clay sandwiched between two geotextiles or bonded to a geomembrane, these products are seeing use as a composite component beneath a geomembrane or by themselves as primary or secondary liners.

Geopipe – Perhaps the original geosynthetic material still available today is buried plastic pipe.  Plastic pipe is being used in all aspects of geotechnical, transportation, and environmental engineering with little design and testing awareness, probably because of a general lack of formalized training.  The critical nature of leachate collection pipes coupled with high compressive loads makes geopipe a bona fide member of the geosynthetics family.  Its function is clearly drainage.

Geocomposites – Combinations of geotextile and geogrid; geogrid and geomembrane; geotextile, geogrid, and geomembrane; or any one of these three materials with another material (e.g., deformed plastic sheets, steel cables, or steel anchors) are geocomposites.  This exciting area brings out the best creative efforts of the engineer, manufacturer, and contractor.  The application areas are numerous and growing steadily and they encompass the entire range of functions for geosynthetics: separation, reinforcement, filtration, drainage, and liquid barrier.

“Geo-Others” – Innovations in geosynthetics have created products that defy categorization.  These “geo-others” include such products as threaded soil masses, polymeric anchors, and encapsulated soil cells.  The geo-other name is not one specific area, although similar to geocomposites, its primary function is product-dependent and can be any of the five major functions of geosynthetics.  The category is ‘temporary housing,’ if you will, for any new products.  When it is determined the appropriate family, it is moved to “permanent housing.'”

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