Stability analysis of reservoir slopes under fluctuating water levels using the combined finite-discrete element method

Fluctuating water levels are responsible for many reservoir slope failures. This work develops a novel slope analysis model (Y-slopeW) to evaluate the reservoir slope stability under water-rock coupling effect, based on the combined finite-discrete element method (FDEM). The transient fluid fields under water level fluctuations are first calculated, and then slope stability under water-rock interaction is evaluated in terms of the safety factor using the strength reduction method. Several benchmark tests are proposed to validate the present model. Stability analysis of an ideal slope under reservoir water level fluctuation is analyzed, where the effect of reservoir fluctuation rate and rock permeability coefficient on slope stability are discussed in detail. A practical slope case (Majiagou slope) in the Three Gorges Reservoir area is studied. Results show that the fluctuating reservoir water level plays an important role in slope stability, and a rapid drawdown is the most unfavorable condition to the slope stability. The work detailed herein proposes an efficient tool to better understand the failure mechanism and stability evolution for slopes under water level fluctuation.