Frost Deformation and a Quasi-Elastic-Plastic-Creep Constitutive Model for Isotropic Freezing Rock

Freeze-thaw weathering of rock masses in cold regions is mainly caused by the freezing deformation of rock exposed to subfreezing temperature. The deformation behavior of freezing rock is focused on in this research. The phase transition process of the water-ice system in freezing rock is analyzed. A time-dependent variable named freezing degree is applied to describe the percentage of water phase changed into ice in the rock. The mechanical character of the freezing rock is investigated based on compression tests of freezing sandstone. Accordingly, the strength and yield criteria for freezing rock are analyzed. Next, a quasi-elastic-plastic-creep model is proposed to describe the time-dependent behavior of freezing rock. The total strain of freezing rock is decomposed into three parts, including the thermal strain of the rock matrix, the strain caused by the confining pressure, and the freezing strain caused by the phase transition of water in the rock. The freezing degree function is applied in the constitutive model, which is further redeveloped using the programming language VC++. Finally, a tunnel in a cold region is simulated using the new constitutive model. The result indicates that the new model can simulate the time-dependent behavior of freezing rock.