Yield stress and volume change behaviour of unsaturated soils

The SFG model (Sheng et al., 2008) provides a consistent explanation of yield stress, shear strength and volume change behaviour of unsaturated soils as functions of suctions. All these functions are based on one single equation that defines the volume change with suction and stress changes. This paper provides a systematic validation of the equation against experimental data. The experimental data used in the paper include those for samples prepared from slurry soils and compacted soils. It is shown that (1) the method currently used to determine yield stresses of unsaturated soils is incorrect, and (2) volume change behaviour of unsaturated soils can well be predicted by the SFG model.