Francis. It incorporates referee's comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document.

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.

This paper reports a field trial of membraneless vacuum preloading and fill surcharge to improve a compressible clay layer below sand fill at a reclaimed land site in Singapore. The thickness of the soft clay layer varied from 4 to 17 m. Due to the sand fill, a vacuum was applied to the clay layer using a proprietary membraneless method. Four weeks after the vacuum load was applied, a 2·5 m thick layer of sand fill was added as surcharge. Ground settlements, settlements and pore pressures at different depths in the soil were measured during the soil improvement. The measured field settlements and pore-pressure data were used to compute the degree of consolidation. The calculated values were found to differ considerably, the reasons for which are discussed. Experiences and lessons learned from the project are also highlighted.

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