The Influence Research Of Soil Seepage On Slope Stability Under Reservoir Drawdown Condition

Since the tragedy of the Voiont reservoir caused by the bank slope landslide happened, the research on the stability of slopes under the conditions of reservoir water level change have drawn a lot of attention, and by now many academic achievements have been made, which include experimental research and theoretic research by calculation. For the aspect of theoretic research by calculation, the study focused on the application of Strength Reduction Method to solve the stability problem of the reservoir slope, lots of literature have discussed this, but there is still some problem existed. For example, the coupled calculation between seepage field and stress field, the lack of quantitative standard for the failure criterion of the Strength Reduction Method, and the research on the unsaturated soil seepage characteristics’ influence on the slope stability is few. As mentioned above, The main content of the thesis is as follows:(1) Fluid-solid coupled theory for the pore medium and its finite element form were introduced. The Strength Reduction Method was elaborated and the failure criterions of which were discussed, and a new failure criterion for the reservoir slope stability analysis under the condition of water level change have been proposed, which makes the critical criterion quantitative;(2) The ABAQUS finite element program is secondary developed to achieve the reservoir water level boundary condition which changes with time, and based on which a homogeneous soil slope model with water level change was built. While the seepage coefficient in the unsaturated region is considered unchanged, the influence of the different saturated seepage coefficient on the phreatic line and on the slope stability as well is analyzed, when the reservoir water level drawdown rate is set as1m/day.(3) The soil-water characteristic curve and the unsaturated seepage coefficient was calculated by applying the estimated calculation method proposed by Fredlund and Xing. And the3parameter in this method was analyzed to show their effect on the soil-water characteristic curve and the unsaturated seepage coefficient. The material parameters calculated from this estimated method was applied to the slope model, and a reservoir slope model under the condition of unsaturated and unsteady seepage was set up. Based on this model the influence of3undetermined parameters in the estimated calculation method on the phreatic line and Factor of safety was analyzed. Also this analysis is compared with the saturated seepage only analysis.(4) The unsaturated unsteady seepage model built was applied to the finite element calculation and analysis for the Shazizhai reservoir danger control and reinforcement project. According to the requirement of the national standard the seepage stability and the anti-sliding stability was checked, and the calculation conditions proposed by the standard are expanded, the seepage stability and the anti-sliding stability under different drawdown rate of the water level was also considered. Several seepage reinforcement method for the earth and rock dam was introduced, and a proper plan was chosen for this project. A finite element model was also built for the reinforced dam, and the seepage stability and the anti-sliding stability was also analyzed under the conditions required by the national standard as well as under the conditions with different water level drawdown rate.65Figures,6Tables,80Reference.