Innovative Soft Soil Improvement Method through Intelligent Use of Vacuum De-Watering and Dynamic Compaction Techniques

Abstract

Recently, an innovative soft soil improvement method was advanced in China by integrating and modifying vacuum consolidation and dynamic compaction ground improvement techniques in an intelligent and controlled manner. This innovative soft soil improvement method, often referred to as “High Vacuum Densification Method (HVDM)”, has been successfully used in China and Asia for numerous large-scale soft soil improvement projects, from which enormous time and cost savings have been achieved. In this presentation, the working principles of the HVDM are described, followed by a summary of two case studies. Results of numerical simulation using FLAC3D computer program, in which dynamic compaction is modelled as a three-dimensional, coupled hydro-mechanical model, are presented to highlight the mechanisms of positive pore pressure generation due to dynamic compaction. Both field studies and numerical simulation results support the mechanisms of HVDM in that dynamic compaction induced positive pore water pressure together with vacuum generated negative pore water pressure have added effects in rapidly expelling water out of the soil, thus increasing density (reducing void ratio) and improving undrained shear strength of soft, fine-grained soils in a relatively short duration.