Damage constitutive model of freeze-thawed rock considering the characteristics of void compaction

The deformation of rocks in the nonlinear compaction phase varies significantly under the action of complex environments. In order to better describe the various stages of deformation and damage characteristics of the loaded rock in the cold zone rock engineering, the change rule of axial strain difference and axial strain is analyzed, and a method of determining the threshold point of rock stress is established. Based on the intergranular bond fracture model to define various types of damage variables, the damage evolution equations under freeze-thaw-loading were derived segmentally with the void closure point as the boundary, and the deformation of the rock is regarded as consisting of the deformation of the void and the solid particles, so as to establish a damage constitutive model of freeze-thawed rock with the consideration of the void compaction characteristics. To verify the rationality of the model, uniaxial compression tests of sandstone under FT cycles are conducted, the deformation characteristics and damage evolution pattern of rocks under freeze-thaw (FT) cycles are analyzed. The results show that the theoretical curves of the constitutive equation are in good agreement with the experimental curves, which reflect the whole process of deformation and failure of rock under freeze-thaw loading, and can characterize the influence of FT cycle and pore compaction on the deformation characteristics of rock.