Time-dependent degradation mechanisms and instability prediction of dangerous rock mass on reservoir banks under multiphase hydro-mechanical coupling effects

Time-dependent assessment of dynamic instability, rockburst phenomena, and potential collapse of unstable rocky reservoir banks presents the critical engineering challenges under multiphase hydro-mechanical coupling effects. While existing research has primarily focused on reservoir bank instability under static water level conditions, it has largely overlooked the process of time-dependent material degradation in stability assessment frameworks. This study addresses this knowledge gap through an integrated approach combining numerical modeling and experimental investigation. A finite element model was developed based on the Jianchuandong Rock Mass (JRM), incorporating hydrostatic pressure variations and strength reduction techniques. Complemented by controlled dry-wet cycling experiments simulating reservoir water fluctuations, the research quantitatively evaluates the coupled effects of hydraulic variations and progressive rock deterioration. The results reveal significant temporal coupling between water level fluctuations and rock mass degradation, which mutually accelerates the destabilization process and ultimately leads to instability in the fifth hydrological year. The findings demonstrate that the proposed framework effectively captures the hydro-mechanical coupling mechanisms underlying reservoir bank behavior. This multi-field coupled analysis methodology achieves marked advancements beyond traditional static approaches through explicit consideration of time-dependent geotechnical mass deterioration characteristics, providing technical support for the lifecycle assessment of long-term operation water conservancy projects. • Time-Dependent Degradation Mechanisms of Reservoir Banks • Stability Prediction of Dangerous Rock Mass • Quantification of Multiphase Hydro-Mechanical Coupling Effects