A microstructure-dependent hydro-mechanical coupled constitutive model for unsaturated soils

Stress and hydraulic paths significantly affect the microstructure of unsaturated soil. On the other hand, different pore types and structures also have different impacts on mechanical and hydraulic behavior of soils with double-pore structures such as expansive soils and compacted soils. Based on the hydro-mechanical coupled constitutive model developed by Wheeler (GCM), the effective degree of saturation considering the different effects of macro and micro pores on the hydro-mechanical characteristics is introduced into the Bishop effective stress equation to take the influence of pore structure into account. On the basis of the effective degree of saturation, a microstructure-dependent hydro-mechanical coupled constitutive model for unsaturated soils is then proposed. The performance of the model is verified by various experimental data of isotropic compression tests and the predictions match the observations well, indicating the validity of the proposed model.