Slope Stability Analysis As Water Level Change And Rainfall

The slope stability problem is a classic one of the three major problems in geotechnical engineering field. Slope generally includes natural slope and artificial slope. In design of highway, dam and reservoir bank dike engineering, it becomes a difficult problem to obtain the safety coefficient expressly when considering the water level change and the complex factors such as rainfall. This paper uses the finite element limit equilibrium method proposed by professor Shao in analysis of the seepage slope stability considering fluid-solid interaction. As a kind of deterministic stability analysis methods based on limit equilibrium conditions, it gets the stress field through the numerical method (finite element and discrete element or boundary element, etc.) firstly, and then according to the definitions of safety factor, we can search the most dangerous slip surface using the mathematical programming method. The physical meaning of safety factor definition is clear in the method, it combines the advantages of the limit equilibrium method and finite element method (FEM), as long as the stress field is obtained, it can be convenient and quick to find out the safety coefficient, the method is very suitable for engineering calculation and its advantages are more obvious in the stability analysis under complicated conditions.The overall framework of the paper carries out mainly in three parts:1. Illustrate research background, research status at home and abroad about slope stability under the influence of water, including numerical and experimental study about slope instability caused by water level changes and rainfall, and review the research content.2. Summarize the slope stability analysis methods in two aspects:the traditional method and the finite element method. With a homogeneous slope standard example, this part compares the results of traditional method and the finite element method (FEM), and also introduces a variable reduction method for strength calculation and verifying the rationality of the results.3. Slope stability analysis under the condition of unsaturated seepage, including:1) The unsaturated soil consolidation theory and numerical methods in the thesis, including the principle of effective stress about unsaturated soil, saturated and unsaturated soil seepage and coupling method and unsaturated unsteady seepage in the processing of boundary conditions and initial conditions.2) Based on Griffith's example in 1999, complete a steady seepage slope stability analysis by the finite element strength reduction method and the finite element limit equilibrium method, and compare the results with traditional limit equilibrium method.3) Based on Griffith's example, considering three kinds of mode proposed by other researcher, the ideal rapid drawdown mode, the ideal slow drawdown mode, and the drawdown under unsaturated and unsteady seepage, this part studies the influence of reservoir water level drawdown on slope stability, the calculation also considers the impact of some factors on the safety factor, such as water level drop height ratio. This part analysis the safety coefficient variation during pore pressure dissipation after rapid drawdown, using the finite element limit equilibrium method, and compare with the results of finite element strength reduction method.4) Slope stability analysis under the condition of rainfall in which the rainfall intensity are respectively 100 mm/d,200mm/d and 300mm/d;:a) A highway slope calculation with actual soil parameters, using finite element method to obtain the field of pore water pressure, seepage velocity and the temporal variation of equivalent plastic strain under different rainfall intensity, reflecting the progressive failure process of a slope under rainfall, b) Complete stability analysis for the slope during rainfall with the finite element limit equilibrium method and the finite element strength reduction method, obtain the variation of the slope safety coefficient and slip surface, c) With the finite element limit equilibrium method, this part studies stability of the slope under rainfall in which the rainfall intensity is close to the saturated permeability coefficient considering the slope Angle, the influence of the hydraulic parameters.