Drawdown of groundwater table causes the changes of net mean stress and matric suction in unsaturated soil

and then induces volume change of soil mass. By using the GDS unsaturated triaxial apparatus

the total volume change and water content change of the remoulded unsaturated soil in the test are studied in the drying process. For a typical foundation pit

ABAQUS is used to simulate two dimensional saturated-unsaturated steady-state seepage flows induced by foundation pit dewatering. Based on test and simulation results

using Fredlund constitutive model and effective stress theory

subsidences of unsaturated soil and saturated zones are estimated respectively for different drawdown depths. Computed results indicate that in total amount of subsidence

the portion of subsidence of unsaturated soil zone cannot be ignored. The contributions of unsaturated soil zone to total subsidence increases as drawdown depth increases.