Numerical Analysis On Slope Seepage Field And Stability Under Rainfall Infiltration

The rainfall is one of the main causes of sliding failure of slope. Obviously, there is a close relationship between rain infiltration and slope sliding. This research on stability of slope during rainfall has been concerned and valued by the scholars of internal and overseas. Slope instability during torrential rain or long-lasting rain bring large damage to people’s lives and property, It is important for researching and predicting the sliding failure of slope to analysis the development of seepage field and instability of slope during rainfall. In the thesis, with saturated-unsaturated seepage theory, the changing regularity of seepage field is studied under the condition of rainfall, and the studies conclude the formation and variations of the slope volumetric water content, transient saturated region and pore water pressure. And the changing process of slope stability is carried out with the method of combining the seepage calculation of finite element and limit equilibrium. Then, the sensitive analysis for influential factor of slope seepage field and stability is made. Finally, the thesis analyzes the failure mechanism of slope under coupling effect of earthquake and rainfall. Research efforts have been carried on as follow:1The basic study on saturated-unsaturated seepage theory. Based on the Darcy’s law and the energy conservation law, the saturated-unsaturated seepage differential equation and the solution conditions are summed up. And this is taken as the basis of finite element numerical simulation.2The finite element analysis of development law of slope field on the condition of rainfall. In the thesis, the changing process of slope volumetric water content and pore water pressure are calculated on the condition of rainfall by two-dimensional finite element software. Moreover, the four influencing factors, rainfall intensity, duration, gradient and slope height are studied. The calculating results show that soil on the surface of slope is mainly affected under rainfall, and the first response to rainfall is the bottom of slope, then is the top of slope, finally is the internal soil of slope.3The analysis on slope stability on the condition of rainfall. Combined the seepage calculated result of finite element with the theory of unsaturated shear strength, the dynamic variation of slope stability under rainfall is analyzed by limit equilibrium method. Certainly, the changing rule of slope stability during rainfall at different rain condition and slope characteristic are also concerned. Some conclusions are drawn as follow:first, the safety factor of slope stability is decreased under rainfall; second, the minimum safety factor of slope is not appeared at the instant of rain stopped, but exhibits hysteresis, and rises again after rainfall.4The sensitivity analysis of influencing factors of slope seepage and stability. The influencing factors of slope seepage and stability, rainfall condition and slope characteristic, are calculated by grey relational analysis method. The useful conclusion is obtained:first, the rainfall intensity and duration are the main influence factors of slope seepage and stability; second, the rainfall intensity and duration need to be regarded as the main object in the optimum design of slope and landslide disaster prevention.5Analyze the failure mechanism of slope under coupling effect of earthquake and rainfall. By using numerical analysis method, this part calculates and analyzes the slope seepage and stability on the condition of the rainfall after an earthquake. The result shows that:first, the earthquake makes slope geotechnical body to produce permanent deformation and increase the permeability coefficient of slope, moreover, the rainfall infiltration will further decrease shear strength of slope, lead to the emergence of landslide. The earthquake combines with rainfall is more easily to induce landslide than single factor.