Methods for improvement of clay slurry or sewage sludge

Clay slurry or sewage sludge may be used as fill materials for land reclamation. However, the treatment of very soft materials of high water content is difficult. One major difficulty is how to create a working platform on top of the slurry layer for required soil improvement works such as vacuum preloading to be carried out. Several methods that can be used to create a working platform on top of a slurry layer are reviewed in this paper. These include (1) sun drying; (2) capping with sand or other good soil; (3) use of geotextile; (4) cement mixing; and (5) dewatering using drainage. The advantages and disadvantages of each method are elaborated. Practical examples are given to illustrate the application of some of those methods. Sewage sludge is more difficult to treat because of its organic content and a combined chemical and mechanical method needs to be used. Two conceptual methods for using sewage sludge and other waste materials for land reclamation are also proposed.