Stability Analysis And Prediction Of Dashishu Landslide In Xiaolangdi Reservoir

The Dashishu landslide is located at the Xiaolangdi reservoir,upstream 7km the Xiaolangdi dam.A significant instability volume of about 450×10⁴m³ occurs in the deformation and crack area,the potential sliding volume is about 1915×10⁴m³.In thispaper,engineering geological analysis,rigid limit equilibrium analysis,three–dimensional numerical calculation and other means are used to analyze and evaluate the stability of the landslide and to predict its deformation trend.The main research contents and results are as follows:?1?The engineering geological analysis method is used to analyze the engineering geological conditions of the landslide area,the development characteristics of the landslide,and the mechanism of instability and deformation.It is preliminarily determined that the Dashishu landslide is the resurrected body of Shuiquantou ancient landslide,and which damaged mainly in the form of traction creep failure.It is a large bedrock landslide developed in the bedrock slope area,and the further development of Dashishu landslide will be promoted by the fluctuation of reservoir water level,the infiltration of rainfall and the influence of groundwater activity.?2?The Geo-studio program of the limit equilibrium method was used to analyze and evaluate the stability of the Dashishu landslide under different conditions.The results show that Dashishu landslide is in a stable state under the natural condition,the rainstorm condition and the reservoir water level plummeting condition.The shallow landslide of the Dashishu is instable while the deep landslide of the Dashishu is stable under the coupled earthquake and rainfall earthquake conditions.?3?Based on FLAC^3D fast Lagrangian difference software,the deformation and stress distribution characteristics and stability of the Dashishu landslide under different conditions are compared and analyzed.For the high water storage,earthquake has the greatest impact on its stability,then the sudden drop in rainfall and the reservoir water level dropped suddenly.Under the condition of a sudden drop in reservoir water level,the plastic zone of the landslide body develops strongly.Compared to the natural state,the distribution cloud map of the plastic zone gradually shifts to the leading edge of the landslide,and the shear strain increases obviously.Under the condition of rainfall,the shear strain increment cloud map and plastic zone cloud map increases along the downward direction of the landslide trailing edge,and the displacement also increased obviously.The suddenly drop of reservoir water level mainly impacts on the front and middle part of the landslide body,and the rainfall mainly impacts on the tensile crack at the back edge of the landslide.?4?The analysis of the monitoring data of Dashishu landslide shows that the deformation curve of the back edge of the slope is characterized by obvious"step"development,and there are sudden changes in June and July every year.Metabolic model based on the equivalent time equidistant GM?1,1?prediction model has been analyzed and evaluated based on the landslide deformation monitoring data.The results show that the equidistant GM?1,1?prediction model can be carried out in short-term.