Hydromechanical Constitutive Model for Unsaturated Soils with Different Overconsolidation Ratios

Overconsolidated unsaturated soils emerge in many engineering problems. This article presents a constitutive model for unsaturated soils using skeleton stress and degree of saturation as fundamental variables. A subloading surface is introduced into the framework to interpret the effect of overconsolidation on the coupled hydromechanical behavior of overconsolidated unsaturated soils. The main advantage of the proposed model is that it is capable of reproducing the hydromechanical behavior of unsaturated soils with different initial overconsolidation ratios, such as the overconsolidation effect on the shearing-induced saturation change. The material parameters of the proposed model can be calibrated through conventional tests. Numerical studies were conducted to assess the performance of the model for a fictional silt under two typical scenarios. The validity of the proposed model was confirmed by experimental results for both isotropic and triaxial conditions reported in the literature.