Sediment Retention and Clogging of Geotextile with High Water Content Slurries

Abstract

Over the past two decades, geotextile tube dewatering has been predominantly used for dewatering high-water content slurries, fly ash, and different types of sediments and sludges. The water content of these dredged sediments can be as high as 800% and their shear strength is very low before dewatering. The selected geotextile should be tight enough to allow for minimal, clog-free sediment piping and to maintain steady drainage through the geotextile tube. These steps ensure good sediment retention of high water content slurries and provide an adequate discharge capacity of geotextile tubes during dewatering. This study investigates the sediment retention and geotextile clogging of high water content slurries (232.56, 400 and 882.35%). A falling head test (FHT) was used to evaluate the dewatering performance of six pairs of woven and non-woven geotextiles with similar pore openings but different pore size distributions. FHT showed that the piping rate increases with decreasing water content in a slurry (232.56–882.35%) and the degree of clogging decreases with increasing pore sizes (both O50 and O98). In addition, a study was carried out to measure the pore size distribution of 51 geotextiles using capillary flow tests. The capillary flow test results are correlated to mass per unit area of geotextiles, a property of geotextiles which is easy to measure. It was found that O98, O50 and O10 of non-woven geotextiles decrease with the increasing mass per unit area. However, no such trend was found for woven geotextiles.