A Micromechanics-Based Damage Model for Freeze–Thaw Rock Considering Moisture Migration

Under the freeze–thaw cycle, violent moisture migration will occur inside the rock mass, which will change the state of microcracks in the rock mass and ultimately affect its macro-mechanical behaviors. In this paper, the amount of moisture migration was introduced into the thermodynamic system as an intrinsic variable. Based on the friction-damage coupling model, the micro-elastoplastic damage constitutive model considering moisture migration was derived. The proposed model was verified by conventional triaxial tests of rocks under different freeze–thaw cycles and the model can satisfactorily simulate the stress–strain curve of the rocks. The amount of moisture migration under different freeze–thaw cycles is related to the porosity of rock masses. The elastic modulus, compressive strength and plastic strain at the peak strength are all linearly related to the amount of moisture migration. Moisture migration can reduce the strength characteristics of the rock and increase its plastic deformation. The model considers the moisture migration mechanism inside the rock during the freeze–thaw cycle and the micro-physical mechanism of rock failure. Therefore, the parameters in the model have clear physical meanings.