Abstract:

A pressure plate method and vapor equilibrium technique with saturated salt solutions are used to investigate the water retention behavior of Shanghai soft clay in a wide suction range. From the relation between suction and degree of saturation, the air entry value is about 580 kPa and residual suction value is about 13.8 MPa for Shanghai soft clay layer. A method for determining air entry value using the relation between suction and water content is proposed, which is practical for the specimens with large volumetric shrinkage or deformation due to drying. Based on the deformation characteristics of the soil, the air entry value is about 600 kPa and residual suction value is about 13 MPa determined by using the above method, which is consistent with actual values. The air enter value and residual point of the specimens are determined with large volumetric shrinkage or deformation difficult to measure due to drying, as proposed by the water content versus suction relationship. This method can be used to avoid the effect of the volume measurement on the determinationof the air entry value and residual point.

Key words: Shanghai soft clay, unsaturated soil, soil-water characteristic curve (SWCC), air entry value, wide suction range