Dewatering Fly Ash Slurries Using Geotextile Containers

The design of geotextile containers for dewatering applications typically requires good retention of the confined fill material solids. This becomes difficult to achieve when the fill material is fine grained and the pore openings are large. Furthermore, the proper retention becomes critical if the confined material is contaminated. Fly ash is one of the fine-grained geomaterials that exhibit behavior that is different from regular soils because of differences in its particle structure and chemical composition. A laboratory testing program was conducted to evaluate the retention performance of geotextiles with fly ash slurries. The results indicated that fly ash could be successfully retained by a variety of woven geotextiles and nonwoven/woven combinations. Results also showed that use of a double-layer geotextile system, rather than a single woven geotextile, significantly increases the retention capacity.