The effect of fine soil content on the filtration characteristics of geotextile under cyclic flows

The use of geotextiles as filters for revetments or embankments has become popular. The geotextile filter must be permeable enough to drain water effectively, but it also has to retain the soil particles to prevent them from being washed out. In the research on the filtration function of geotextiles, retention and permeability criteria have been proposed. Most of the research has considered conditions that are simpler than real in situ conditions, such as cyclic flows due to the fluctuation of water table caused by sea waves, boats, or periodic drawdown of water for irrigation purposes. Moreover, soils with different fines contents will cause dissimilar soil erosion behaviour in a revetment that uses geotextiles. For this reason, a cyclic flow apparatus is adopted in this research to take account of the effect of overburden pressure and cyclic flows on soils. The soil samples are composed mainly of sand, with 0–10% fines content of silts and clays. The applied cyclic flow periods range from long to short, in order to simulate a range of waves. The results show that the fines content has a significant effect on the filtration behaviour of a soil–geotextile system. In addition, the normal pressure and cyclic flow period have an influence on the performance of the geotextile filter.