Research On Slope Stability Of No.Ⅶ Deposit Slope Of Lawa Hydropower Engineering

The paper selects Deposit Ⅶ as the object of study,which is on the left bank and downstream of Lawa Hydropower Project,a project on the upstream of the Jinsha River.As the largest deposit in the project area,Deposit VII has a total volume of 27.20 million m3.Based on the processing and analysis of the collected previous project investigation data,it’s believed that the overall stability,geologic structure,and slope deformation mechanism of the deposit would greatly affect the dam site and dam type selection and permanent structure layout of Lawa project.Therefore,study of the essential characteristics and formation mechanism of the deposit,detailed deposit stability analysis and calculation,and judgment by specifications and standards will be of great significance to the construction and long-term safe operation of Lawa project.The main results of the study are summarized as follows:(1)The stratum geological parameters required for establishing the calculation model have been obtained by analyzing and studying Deposit Ⅶ in terms of topography and landform,lithologic characteristics of stratum,rock mass structure and deformation mechanism on the basis of the previous investigation data of Lawa project and by processing and summarizing the available geological data and the parameters of similar projects;(2)With rigid body limit equilibrium method adopted for 2D calculations in this paper,calculations have been conducted for overall stability,upper-and lower-layer stability along the slip zone and the local surface layer stability of three selected typical geological profiles by several methods with Slide software,and analytical judgment has been made for the results obtained;moreover,for the impacts of internal friction angle and cohesive force on the safety and stability of the slip zone,a sensitivity analysis has been carried out;(3)Finite element numerical analytical calculations for the three selected profiles have been performed with ANSYS software,and then scientific and rational judgment has been made through analyzing and comparing the obtained results of the overall stress,strain,deformation and vector characteristics of the three profiles and the stress,strain,deformation and vector characteristics of the slip zones under three operating conditions;meanwhile,the strength reduction method has been adopted for the calculation of slip zone stability.(4)For Deposit Ⅶ,the results of qualitative and quantitative analysis and study by several methods indicate that the stability coefficients under the three calculated conditions are greater than the permissible safe values stipulated in the specifications,and the overall stability of the deposit is relatively satisfactory.However,local small-scale shallow-layer slide may occur on the surface layer,so it’s required to intensify the monitoring.