Influence of Morphology of Sliding Surface on Its Seepage Characteristics and Slope Stability Under Fluctuations in Reservoir Water Level

The fluctuation in reservoir water level is one of the key external factors affecting the stability of slopes. Finite element models are established for four typical slope types in the Three Gorges Reservoir area (line-shaped, arc-shaped, polyline-shaped, and chair-shaped), and the seepage characteristics and slope stability under different permeability coefficients are simulated. The results reveal the following: (1) The shape of the infiltration line is closely related to permeability. The infiltration line presents a convex shape when the permeability coefficient is lower than the rate of reduction in the reservoir water level, and a concave shape when the coefficient is higher than this rate. However, the infiltration line always presents a convex shape under the condition of increasing reservoir water level. (2) The wetting rate decreases with the increase in the permeability coefficient and attains its minimum value under the conditions of line- and arc-shaped slopes. (3) The slope safety factor first decreases and then increases with the decrease in the reservoir water level. Meanwhile, the converse occurs when the reservoir water level increases. (4) When the reservoir water level decreases, the line-shaped slope with a marginal permeability coefficient is the most hazardous, whereas the chair-shaped slope with a high permeability coefficient is the safest. (5) When the reservoir water level increases, the slope becomes unstable after the stable stage of the reservoir water level.