System reliability analysis of landslides subjected to fluctuation of reservoir water level: a case study in the Three Gorges Reservoir area, China

Reservoir-induced landslides are a common type of geological hazards in the hydropower area, where the frequent occurrence of catastrophic landslides has attracted widespread attention. This study focuses on the Huangtupo Riverside Slump 1#, a reservoir-induced landslide in the Three Gorges Reservoir Area of China, which has been investigated with double sliding surfaces. First, a series of numerical analyses are conducted to obtain the seepage field inside the landslide subjected to fluctuation of reservoir water level. Then the stability of the landslide is analyzed by employing the results of the seepage field. Subsequently, considering the uncertainty of strength parameters of sliding surfaces, the failure probabilities for the individual sliding surfaces are assessed via first order reliability method, and then the system reliability of the landslide is analyzed by applying the Ditlevsen's bounds method. The results indicate that the change of seepage field is closely related to the scheduling of reservoir water level and lags behind the scheduling, which has a greater impact on the stability of the 1-1# failure surface than the 1-2# failure surface. Similarly, the bounds of system failure probability vary with the reservoir water level, and the most dangerous probability occurs when the water drops to the lowest level. Evaluating the landslide from the perspective of system reliability greatly narrows the risk range, which has potential for further application in risk management and control. Besides, the relationships between the correlation coefficient of strength parameters and the landslide system response are discussed through parametric analyses.