Damage mechanism of jointed rock masses in reservoir area under combined action of dry-wet cycles and dynamic loading

Abstract

[Objective] The reservoir-induced earthquakes caused by the impoundment and geological hazards such as reservoir bank landslides triggered by fluctuations in reservoir water level frequently occur. To accurately assess the impact of the Baihetan hydropower station construction on slope stability in the reservoir area, it is imperative to investigate the degradation characteristics of jointed rock masses under the combined action of dry-wet cycles and dynamic loading. [Methods] Based on this, for jointed dolomite and jointed sandstone collected from typical landslides in the Baihetan reservoir area, laboratory tests were conducted to systematically analyze the damage mechanisms of jointed rock masses under dry-wet cycles and dynamic loading, considering different lithologies and damage cycles. [Results] The result showed that under the combined action of dry-wet cycles and dynamic loading, the jointed rock masses rapidly degraded in the first three cycles. The shear strength degradation rates reached 25.5% for jointed sandstone and 22.3% for jointed dolomite. After five cycles, the degradation degree tended to stabilize. Under twelve cycles, the degradation rates of cohesion and internal friction angle of jointed sandstone rock masses reached 22% and 13%, and those of jointed dolomite rock masses both reached 33%. [Conclusion] The result indicate that the degradation of jointed rock masses is primarily controlled by mineral dissolution caused by dry-wet cycles and the abrasion of structural planes induced by dynamic loading. The degradation caused by dry-wet cycles is more pronounced for the jointed sandstone. Under low normal stress, more severe abrasion on sandstone structural planes is caused by the dynamic loading, whereas under high normal stress, higher damage degree of dolomite is caused by the dynamic loading. Under the combined degradation, the shear strength degradation rate of jointed sandstone is greater than that of jointed dolomite. However, this difference in strength degradation rates between the two rock types diminishes with increasing normal stress. The mechanical properties of jointed rock masses are significantly degraded by the combined action of dry-wet cycles and dynamic loading, and affected by lithology, normal stress, and the number of cycles. This provides an important theoretical basis for slope stability assessment and disaster mitigation in the Baihetan reservoir area.

Keywords

jointed rock masses / dry-wet cycles / dynamic loading / shear strength / degradation mechanism / mechanical properties / damage cycle / landslide