A new test apparatus for the study of geotextiles behaviour as filters in unsteady flow conditions: relevance and use

In many applications, geotextiles are subjected to cyclic hydraulic loads, for example, when used as revetment filters. A new test apparatus has been developed to investigate the influence of a cyclic component in the hydraulic gradient and the effect of boundary conditions. The boundary conditions to be considered in such applications of geotextiles are mainly the normal effective stress and the type of contact, which can be more or less continuous. The test apparatus presented in the paper is capable of reproducing these conditions while imposing a cyclic gradient. A set of tests have been performed using the apparatus in cyclic flow conditions perpendicular to the filtering interface: typical test results are also presented in the paper.