Damage evolution characteristics of the shear band-bedrock interface under dry-wet cycling: experimental and numerical simulation

Using the “Banbiyan” dangerous rock mass (BDRM) in the Three Gorges Reservoir Area (TGRA) as a research background, this study investigates the damage evolution characteristics of shear band-bedrock interfaces under dry-wet cycling through a combination of dry-wet cycling tests, shear tests, and numerical simulations. The research findings are as follows: The shear band-bedrock interface’s peak shear strength has a negative connection with the frequency of dry-wet cycles and a positive correlation with normal stress. With an increase in dry-wet cycles, the total deterioration of cohesion gradually rises and shows minimal change after 10 dry-wet cycles, while the average deterioration in each stage progressively decreases. The total deterioration of the internal friction angle increases, though the average deterioration in each stage remains relatively consistent. Based on the mineral composition characteristics of the limestone, a mesoscopic parameter degradation formula for the interface under dry-wet cycling was established and validated for reliability. We used this formula in numerical simulations and obtained the microscopic damage phenomena of the interface under different height-to-length ratios and different dry-wet cycles. The variation patterns of peak shear strength, crack quantity, and the total energy changes with different height-to-length ratios under dry-wet cycling were analyzed. A degradation formula for interface shear strength parameters considering different height-to-length ratios under dry-wet cycling was proposed. The results indicate that the height-to-length ratio of the interface has a more pronounced effect on strength degradation than the number of dry-wet cycles. These findings provide valuable insights for studying the overall mechanical properties of shear bands and the stability of dangerous rock masses containing shear bands under reservoir water influence.