Improvement of estuarine marine clays for coastal reclamation using vacuum-applied consolidation method

Consolidation occurs in estuarine marine clays for coastal reclamation by dissipation of the excess pore pressure, which is induced by increasing the total overburden stress during conventional mechanical surcharging. The excess pore pressure can be decreased usually by the use of several construction methods such as sand drain and paper drain. Besides the drain methods, vacuum can also be used in the soil mass to consolidate the estuarine marine clays by decreasing the pore pressure as well as increasing the effective stress.The study on vacuum consolidation is devoted so far mainly for laboratory model tests or numerical analysis in Korea. Recently, an instrumentation system was applied to manage the vacuum-applied consolidation on a field, in which a sewage disposal plant was constructed. While vacuum was applied, the behaviors of estuarine marine clays such as the settlement, lateral deformation and pore water pressure have been investigated precisely. The behavior of estuarine marine clays during vacuum-applied consolidation shows some difference from the behavior of estuarine marine clays in the case of conventional preloading. A principal difference is that the lateral deformation corresponding to settlement is smaller than before vacuum application even though the surcharge height has been increased.