5.1.1 General

The utilisation of polymers in Geotechnical Engineering (a sub-discipline within civil engineering which covers broadly all forms of soil or the earth s crust related problems) constitutes a major range of applications for these materials. The term geosynthetic has been coined to describe the synthetic polymers, almost exclusively thermoplastics, used for geotechnics problems including environmental geotechnology.

The American Society for Testing and Materials (ASTM) has defined geosynthetic in D4439-02 Terminology [1] as follows: a planar product manufactured from polymeric material used with soil, rock, earth, or other geotechnical engineering related material as an integral part of a man-made project, structure, or system. They are generally used in place of, or to enhance the function of, natural soil materials. Common geosynthetic polymers are polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyethylene terephthalate (PET), polyamide (PA), polystyrene (PS) and chloro-sulfonated polyethylene (CSPE). In all cases additives are used as colorants, ultraviolet (UV) light adsorbers, plasticisers, antioxidants, biocides, flame retardants, thermal stabilisers, lubricants, forming agents or antistatic agents [2]. Carbon black and UV stabilisers are the most common additives for protection from weathering.

The main types of geosynthetics are geotextiles, geomembranes, geogrids, geonets, geocomposites and geosynthetic clay liners. Estimations of the market activity of these products in North America between 1970 and 1992 given by Koerner [2] show a continued growth, which is probably still very strong. The amount of geosynthetics used in 1992 in North...