Vibration response characteristics of potentially unstable rock slope induced by high dam flood discharge: a case from Guizhou, China

Flood discharge from high dams can generate fluctuating hydraulic pressures in stilling basins, which may induce vibration responses in adjacent potentially unstable rock slopes. This study investigates the dynamic response of the Dr2 potentially unstable rock slope near Suofengying Hydropower Station in Guizhou, China, under high dam flood discharge. A three-dimensional hydraulic model was first established to simulate the flood discharge and energy dissipation process under the five-gate fully open condition. The fluctuating hydraulic pressure time histories on the stilling basin floor were extracted and introduced into a dynamic numerical slope model. The time series characteristics of hydraulic excitation, displacement, velocity, and residual deformation were analysed. The hydraulic excitation is dominated by low-frequency components, with the main frequency range overlapping the lower natural frequencies of the slope, indicating potential dynamic amplification. The slope response exhibits obvious spatial heterogeneity. Dr2 is mainly sensitive to horizontal deformation, whereas the lower Dr3 rock mass, FJ fault zone, and talus deposit show stronger vertical displacement or velocity responses. Although no sustained dynamic instability occurs under the analysed condition, local deformation concentrations in weak geological zones deserve attention during repeated flood discharge events.