Recent Developments of Vacuum-Assisted Consolidation of Soft Estuarine Clays

For vacuum-assisted ground improvement on highly compressible alluvial or marine deposits, the application of suction pressure accelerates consolidation and controls lateral deformation by isotropically increasing the effective stress. Analytical, numerical, and experimental research on vacuum-assisted prefabricated vertical drains (PVDs) has been conducted at University of Wollongong in past 15 years. Key factors such as vacuum distribution, extent of smear, occurrence of non-Darcian flow, and large-strain effects have been studied and their implications are presented in the paper. Some practical approaches have been proposed to facilitate industrial design schemes for vacuum consolidation. 2D plane strain conversion approach has been proposed for numerical modeling of large soft area treated with multiple PVDs. The behavior of vacuum stabilized soil in the field has been predicted by the numerical models applied to selected case studies through fully-instrumented field trials, by measuring settlement, lateral movement and excess pore water pressure data. A good agreement between the predicted and field data was achieved. Some key theoretical and numerical approaches are presented in this paper, together with the case study involving the Ballina Bypass in Australia.