Geotextiles have been extensively used in hydraulic structures as revetment filters subjected to wave loads. The alternating flow through the geotextile creates a flow regime very different from the unidirectional flow condition that has been extensively studied. The stability of the revetment system depends on many factors, such as the hydraulic properties of geotextile, the initial placement condition, particle size distribution of the subsoil, and the intensity of the wave loads. A new laboratory apparatus has been developed to investigate the influence of the hydraulic conditions on the behavior of soil-geotextile interaction and the stability of the revetment system. This apparatus is capable of simulating cyclic flow conditions normal to the soil-geotextile interface. Two series of tests have been conducted using this apparatus and preliminary test results are presented and discussed in this paper.
The main role of the geotextile as a filter in hydraulic structures such as revetments is to prevent the erosion of the subsoil, while allowing the free drainage of water across the revetments. Hence, the pore size of geotextile should be small enough to retain the soil particles, while large enough for free passage of water. Preferably, the performance of these geotextiles under active wave action has to be evaluated instead of unidirectional flow conditions. Conventional filtration criteria for geotextiles, established for steady flow conditions, state that for a uniformly graded soil, geotextile opening size must be smaller than a characteristic diameter of base soil, say D85 (some times this criterion also involves relative density of subsoil, coefficient of uniformity, etc.). In unsteady flow conditions, the stability of the revetment system depends on many factors, such as the hydraulic properties of geotextile, the grain size distribution and the initial condition of the subsoil, as well as the intensity of the wave loads.