Pre-construction consolidation of soft formation soils by applying a surcharge load alone often takes a long time, thereby impacting the construction schedule. Moreover, attributed to the low permeability and high thickness of low-lying clay deposits, the required surcharge load to achieve more than 90% degree of consolidation can be excessively high over a prolonged period. A system of vertical drains combined with vacuum pressure and surcharge preloading has become an attractive ground improvement alternative in terms of both cost and effectiveness. This technique accelerates soil consolidation by promoting rapid radial flow, decreasing the excess pore pressure while increasing the effective stress.
This lecture presents an overview of the theoretical and practical developments and salient findings of soft ground improvement via PVD and vacuum preloading with applications to selected case histories in Australia, Thailand and China.
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