Experimental study of consolidation properties of unsaturated soils during draining

Changes in groundwater elevation may cause a change in the net normal stress and matric potential within the soil mass, which results in volume changes of unsaturated soil. This research investigated the relationship between the drawdown of groundwater and the characteristics of volumetric compressibility of unsaturated soil. Sand column experiments were designed and conducted to measure the volume changes of coarse and fine sands under different types of drainage conditions at fast and slow drainage rates. The finite element program FEMWATER was calibrated and used to simulate the distributions of stress, tension and moisture content within the sands. Finally, based on the changes of net normal stress and matric potential and the observed volume change of the sands, a least-square method was applied to determine the volumetric consolidation parameters of the unsaturated soils.