A Comparison of Two Unsaturated Soil Constitutive Models in Static Consolidation to Investigate Change of Saturation and Volume

In this paper, the ability and performance of two unsaturated soil constitutive models are compared. One constitutive model is in the context of classical plasticity, and the other constitutive model is in the context of generalized plasticity. The selected models consider the effect of water retention curve on the unsaturated soil behavior. First, a program in FORTRAN language is written for each constitutive model. In the next step, the written program is validated with the experimental results. Finally, eight different suction-stress paths are modeled to identify the strengths and weaknesses of the constitutive models. The results showed that both models could simulate the loading at constant suction, increasing the yield stress and decreasing the soil deformation with an increase of suction. In drying–wetting cycles, the variation of the yield stress of the Sun et al., 2007 model is less consistent with experimental data than the variation of the yield stress of the EBSZ model, and Sun et al., 2007 Model cannot simulate some important properties of unsaturated soils. The EBSZ model cannot simulate a sudden volume reduction (failure) under decreasing suction in unsaturated soils. Using the EBSZ model in the deformation analysis of unsaturated soil may not be reliable.