Numerical Simulation of Slope Deformation Induced by Rapid Drawdown: A Case Study

The rapid drawdown of reservoirs has an unloading effect and can cause slope deformation and failure. The paper investigates the impact of rapid water drawdown on the reservoir bank slopes, using a case study of the Dahua landslide around the reservoir area of the Dahuaqiao Hydropower Station for illustration. Furthermore, a numerical procedure based on the ABAQUS finite element code has been applied to model the coupled hydro-mechanical process. The analysis was undertaken by integration the shear strength reduction technique and transient unsaturated flow modeling. The numerical results show that the rapid water drawdown generates hydrodynamic pressure, which has a crucial impact on the movement behavior of landslides. Landslide deformation is triggered by the "fore-pulling" of rock mass at the slope toe caused by the water level change. Moreover, the calculated factor of safety decreases by about 10.83 percent as the water level drops at an average speed of 2.1 m/day. Based on the numerical simulation results and field monitoring data, the effectiveness of the numerical simulation has been discussed. The calculated values of the cumulative displacement at the three measuring points are 15.07, 9.08 mm and 5.25 mm, respectively. And the corresponding monitoring displacement values are 16.79 mm, 11.06 mm and 5.75 mm, confirming the numerical simulation's reasonableness. In addition, this study can provide a case reference for preventing the recurrence of similar incidents.