A temperature-dependent elastoplastic damage model for frozen sandstone

Abstract

Subzero temperature has a significant effect on mechanical behaviors of rocks. When a sandstone is in subzero temperature environments, the sandstone exhibits temperature-dependent mechanical characteristics due to the freezing of pore water and the shrinkage of mineral particles. To disclose the influence of subzero temperature on the mechanical behaviors of the frozen sandstone, triaxial compressive tests were carried out at four confining pressures (0 MPa, 1 MPa, 3 MPa, 5 MPa) and four subzero temperatures (0 °C, −5 °C, −10 °C, −15 °C). The laboratory tests show that the frozen sandstone undergoes four typical deformation stages from initial loading to failure: compaction, elasticity, yield and postpeak failure stage. With the temperature decreasing, the compaction stage gradually shortens, and the nonlinear behavior of yield stage weakens. The peak strength and initial yield stress of the frozen sandstone increase, and the initial and ultimate yield surfaces expand gradually with decreasing temperature. Based on the deformation features of the frozen sandstone, an elastoplastic damage model is established by considering the effect of subzero temperature on the yield process and deformation. The elastoplastic damage model was calibrated by the experimental data, and the comparisons demonstrate that the proposed constitutive model well agrees with the stress–strain curves at the four subzero temperatures. An exponential evolution law of the macroscopic damage is found in the elastoplastic model, which is totally consistent with the microscopic damage variation monitored by the acoustic emission (AE) technology. Therefore, the temperature-dependent elastoplastic model can well predict the whole deformation behaviors of the sandstone under different subzero temperatures and gives a quantitative description on the damage evolution, and may serve as theoretical references for the construction and safety operation of frozen rock masses in cold regions.