Sensitivity analysis of stability of anti-dip rock slope under fluctuating water level in the Three Gorges Reservoir Area

The fluctuation of water levels in large reservoirs has long been recognized as a critical external factor that affects the stability of bank slopes. However, there have been limited studies investigating the influence of reservoir water level (RWL) fluctuation on anti-dip layered rock slopes. In this study, we constructed a conceptual model by selecting the sandstone in the Three Gorges Reservoir Area (TRGA) as the strata and considering and slope height. Through seepage-stress field coupled analysis, we obtained the seepage field and groundwater lines, and determined the factor of safety (FoS) using the improved cantilever beam limit equilibrium method. We then investigated the variations of the groundwater line and FoS throughout the entire process of RWL rising and drawdown. Our results indicate that the changes in groundwater levels in the slope clearly lag behind RWL fluctuations, with stability improving during the rising stage but deteriorating during the drawdown stage. Range analysis, using the maximum curvature (MaxCurve) of the groundwater level line as the reference, reveals that the permeability coefficient has the most significant impact on the lagging effect, followed by the fluctuation rate, thickness, and dip angle. Similarly, when considering the amplitude of variation in FoS during the entire process of RWL rising and drawdown as the reference, range analysis shows that the permeability coefficient has the greatest impact on stability variation, followed by the fluctuation rate, thickness, dip angle, and slope height.