Abstract: The water level drawdown of reservoir or river often causes the decrease of stability of bank slopes. Establishing a rapid assessment approach for evaluating the stability of slope under the variation of water levels has an important practical significance. Based on the water level drawdown of reservoir or river, and the transient unsteady seepage in clay slope, the program based on shear strength reduction finite element method (SSR-FEM) is developed to compute the factor of safety (FOS) for the slopes under the action of surface water and ground water together. Considering the influences of soil properties, relative permeability ratio and boundary conditions on slopes stability, the relative stability graphic method is presented under the integration parameters of soil properties, relative permeability ratio, drawdown ratio, slope angle, etc. The suggested method can rapidly obtain the FOS of existing slope and the design inclination ratio of planning embankment, and it can also be a helpful supplement for the existing stability charts of simple slope.

Key words: slope stability, SSR-FEM, water level drawdown, graphic-method