Field trial of a membraneless vacuum preloading system for soft soil improvement

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.