The Unsaturated Seepage And Stability Analysis On Slopes At River Banks With The Case Of Xicheng Landslides In Yunyang

The construction of the Three Gorge Dam will greatly change the hydraulic environment at the bank, impact the stability of slopes and induce many geo-hazards. In this thesis, the seepage, stress-strain field and the stability of slopes are analyzed with the case of Xicheng landslide in Yunyang.Prevalently, the finite element method is used for seepage calculation, mainly being based on the saturated seepage. In fact, the unsaturated seepage is also important because the unsaturated part in soil isn't absolutely dry and its physical and mechanical status will vary with the saturation degree of soil. So just dealing with saturated seepage can't make clear the seepage in unsaturated part, and also the entire soil body. In this thesis, seepage is solved by finite element method with the unsaturated soil mechanic theories, of which the result as the hydraulic condition the stress-stain field and the limited equilibrium stability are finished.In seepage analysis, it's abtained that at this landslide the seepage under reservoir water table drawdown or rain conforms to the general flow rules. In details, when reservoir water table rises, water infills from outside to inside of the slope and the phreatic line is concave at first, then tends to flatten when reservoir water table keeps still. When reservoir water table draws down, water outflow from inside to outside of the slope, and the phreatic line is convex, but not very evidently, then comes to flatten when reservoir water table is still. Under the condition of rainfall, and reservoir water table drawdown, the phreatic line rises up to some extent at the rear of the slope, which makes the hydraulic gradient increase and indicates rainfall put impact on the phreatic line in the slope.As for the stress-strain field in the slope, it's acquired that the displacement and shear strain ascend up with the rise of reservoir water table. The stability analysis is based on the limited equilibrium method, ie the general slice method. The change of slope stability is that, the factor of stability increases when reservoir water table rises up, decreases when reservoir water table keep steady. In the course of reservoir water table drawdown, the factor of stability descends whether rainfall or not, till to the stop of reservoir water table drawdown. It begins to increases gradually. Rainfall raises up the phreatic line, enlarge the hydraulic gradient and reduce the factor of stability in the same other conditions.