Constitutive modelling of the time-dependent behaviour of partially saturated rocks

This paper presents a new constitutive model for the time-dependent behaviour of partially saturated rocks. Hydromechanical coupling is formulated in the framework of porous media. Viscoplastic and isotropic damage laws are extended from the original Lemaitre's model using an equivalent pore pressure and an effective stress variable. The model contains a moderate number of parameters which can be identified from the results of typical laboratory experiments. This model can be used for simulating both saturated and unsaturated rocks in a unified manner. It is validated by experimental data obtained from some rocks. Its thermodynamic consistency is also discussed.