Constitutive model for unsaturated fine-grained soils incorporating small strain stiffness

In the paper, we present newly developed hydro-mechanical hypoplastic model for partially saturated soils incorporating small strain stiffness. The model is based on the existing hypoplastic model incorporating very small strain stiffness anisotropy. The model is combined with the hysteretic void ratio dependent water retention model and also with the approach enabling predictions of the very small strain stiffness and stiffness degradation curves. It is demonstrated by simulation of experimental data on completely decomposed tuff from Hong-Kong that the model predicts properly the very small strain stiffness dependency on mean effective stress, void ratio and degree of saturation. Central to correct predictions of suction history dependent stiffness degradation curves is consideration of the dependency of the elastic range size on suction.