Of all the geotextile functions, reinforcement is perhaps the most diversely applied and most technically demanding. Applications vary from comparatively short term , low risk , installations such as unpaved roads ,to long term, high risk applications, such as vertical walls and bridge abutments .This function involves stabilization of soil mass by provision of tensile strength to the soil-fabric system. Geotextile of high tenacity , when placed in a soil mass, takes up some of the tensile stresses and helps distribute them more evenly.
The role of a geotextile as a filter is to permit the free flow of water from one side of the geotextile sheet to the other, without significant long-term loss of soil particles. When filtration is the primary function to be achieved two contradictory mechanisms to be achieved, adequate flow capability and upstream soil particles retention. Adequate flow requires large fabrics pores but soil particle retention requires small fabric pores. Thus, knowledge of both the flow regime and soil characteristics are essential for proper design .Typical applications areas of geotextiles for filtration are pipe underdrains, drainage for retaining walls and erosion control structures.