HYDRO-MECHANICAL COUPLING CONSTITUTIVE MODEL OF UNSATURATED SOILS WITH ARBITRARY DRYING-WETTING PATHS

A large number of tests have shown that after the saturated soil sample enters the hygroscopic stage in the dehumidification process, residual gas would be distributed in the pore of the soil sample in the form of closed bubbles in the high-saturation area. At this time, the soil sample shows great compressibility. When the matric suction is 0kPa after the hygroscopic process, the soil sample would not reach full saturation state. Wei et al. (2008) put forward the constitutive model of unsaturated soil without considering the influence of the residual gas content, and considering the soil sample after moisture absorption process could still achieve fully saturated state, which has certain deviation with the actual situation. In order to simulate the real situation more accurately, this paper proposes a modified constitutive model for unsaturated soils with different residual gas contents. The modified model is based on the theory of capillary hysteresis internal variables and the hydraulic coupling constitutive model for unsaturated soils. The modified model is verified with the measured data and can well simulate the influence of any wet and dry path on the mechanical properties of unsaturated soil.