Analysis of damage evolution and study on mesoscopic damage constitutive model of granite under freeze-thaw cycling

The failure of rocks in seasonal frozen areas under freeze-thaw cycles (FTCs) is a frequently problem in engineering construction, posing a huge threat to the stability of the engineering. In order to explore the mechanism of rock damage degradation. It is necessary to analyze the damage evolution process of rocks and establish an accurate FTCs rock damage constitutive model. Taking the granite in the seasonal frozen zone of Northeast China as the research object, the macro and meso parameters and microstructure of the FTCs granite were analyzed through indoor tests. A new method is proposed to define damage variables considering mesoscopic parameters to establish a mesoscopic damage constitutive model for rocks, further revealing the damage mechanism and failure law of rocks under freeze-thaw load coupling. The research results indicate that in the early stage of FTCs, 20 cycles contribute significantly to the damage and deterioration of rocks, accounting for about 50% of the 80 cycles. After 20 cycles, the degradation trend of various macroscopic and mesoscopic parameters is relatively slow. The residual strain of the rock accumulates as the number of FTCs increases, the brittleness of the rock weakens, and the plasticity strengthens. Based on the established new method of considering mesoscopic parameter damage variables, the viewpoint of introducing correction coefficients based on statistical constitutive models has been validated. After uniaxial compression test data verification, the model has shown good performance. This model expands the damage model of rock freeze-thaw compression coupling effect, providing reference for research on FTCs related to rocks.