Laboratory studies on geotextile filters as used in geotextile tube dewatering

This study is concerned with geotextile filtration as an alternative for conventional disposal methods adopted for the disposal of high water content wastes. In this study, 42 dewatering tests using geotextiles of four different opening sizes were conducted on harbour sediment and fly ash to study the individual influence of factors like water content, gradation of solids, and opening size of geotextile on the over all efficiency of dewatering system. These factors contribute to the compatibility between accumulation of solids in geotextile and dewatering. A critical water content was observed for a given sludge and geotextile at which efficiency of filtration system is optimum. This optimum efficiency is almost the same for the sludges tested comprising of mainly silt size fractions with clay sizes less than 10% and geotextiles used, if the AOS of geotextile is <= 425 mu m. Based on the observations an equation for the determination of critical water content and criteria for the retention of solids were proposed, which are functions of AOS of geotextile and d(15) and d(85) sizes of sludge material in suspensions. (C) 2006 Elsevier Ltd. All rights reserved.