Filtration behavior of geotextile under overburden pressure and bi-directional cyclic flow

To prevent scouring problem of riverbanks, concrete structures such as RC walls have commonly been used. From aesthetic and ecological points of view, however, concrete structures have adverse impacts to the environment. In addition, they are apt to suffer from long-term scouring problem. Therefore, it would be beneficial to seek alternative structures that are safe, economic, as well as having more environmental amenity. One solution is to construct revetments or embankments using geotextiles as filters. These structures consist of a geotextile layer placed on a soil slope, then covered with armor stones. The main function the geotextile performs is filtration. The geotextile must be permeable enough to allow water move freely through the fabric, whilst it also can retain soil particles. Hence, the stability of the structure is ensured. In this research, a series of laboratory tests are conducted with the apparatus which can simulate the geotextiles in the revetments under bi-directional flow. Influencing factors considered are the vertical loading and the period of bi-directional flow that have a definite effect on the stability of revetments. The behaviors of non-woven geotextile with soils of various fine particle contents are studied. The settlement of the soil and the pore water pressures at various depths are recorded. Specimens and the grain size distribution of the soil before and after the test are examined to study the effect of erosion. The purpose is to obtain the load-displacement mechanism of the specimen, thereby to establish appropriate analytical models and design criteria accordingly.