A simplified model for stability analysis of reservoir bank slopes under water level dropping condition

Changes in reservoir water levels significantly influence the slope stability. Determining how to deal with changes in the water level is crucial in slope stability analysis. In this study, the formula for the phreatic line in the slope is derived, and a simplified treatment method for reservoir water level decline is proposed. For this, the slope is divided into different regions, and the values for rock and soil parameters and seepage force are set in these regions. A classical particle discrete element model of the slope is established, the landslide process caused by the reservoir water level fluctuation is analyzed, and the influence of the falling water level speed and duration on slope stability is discussed. The results indicate that for a landslide induced by reservoir water level changes, the slope begins to deform significantly at the junction of the slope and water level line and collapses from the front edge of the slope, thus forming a larger landslide. The maximum displacement of the slope is positively correlated with the drawdown rate of the water level. When the drawdown rate of the water level is low, the largest deformation area is in the unsaturated region. When the drawdown rate of the water level is high, the largest deformation area is at the junction of the slope and water level. The maximum displacement of the slope first increases and then decreases with a continuous decrease in the water level; the most dangerous water level is in the lower one-third–one-fourth of the slope height. The proposed method is simple, fast, and intuitive and can provide a reference for engineering practice.