Study On The Stability Of The Left Bank High Slope Of The First Hub Of Bowa Hydropower Station

Bowa Hydropower Station is located in Muli County,Liangshan Yi Autonomous Prefecture,Sichuan Province.The hydropower station project area is located in the alpine valley area,with abundant mountains on both sides.The topography of the valley is generally narrow and steep,and it is a "V"-shaped valley.The bedrock on the left bank is exposed in a large area,and the landslide accumulation bodies are scattered,and the natural slope is generally large.The geological conditions of the project area are complex,and dangerous rock groups are distributed in many places on the left bank slope,and fragments sometimes slide down.Affected by the earthquake in November,2019,the natural slope on the left bank has experienced two high-level rock collapses so far,which has serious hidden dangers to the safety of local people and the construction of the project area of the first hub of hydropower station.Therefore,it is of great practical significance to study the stability of the high slope on the left bank of the first hub.Firstly,this paper summarizes the research status of slope stability of hydropower stations built in the canyon area at home and abroad,and finds that many scholars have made many fruitful achievements in landslide prevention,deformation mechanism and failure mode of hydropower stations in the canyon area.However,most scholars mostly consider the instability mechanism of the whole slope from the internal rock mass properties of a single slope,or only consider the characteristics of the geographical area where the external slope is located,and calculate the influence of the external environment of the slope on the slope stability.The research content on this is not perfect,so the influence of these aspects on the slope stability should be comprehensively considered.Therefore,in order to meet the research requirements of slope stability of hydropower station,this paper studies the stability of high slope on the left bank of the first junction of Bowa Hydropower Station.Get the following results:(1)The engineering geological conditions of the first junction of Bowa Hydropower Station are introduced from eight aspects.geographical location,topography,hydrometeorology,geological structure,stratigraphic lithology,neotectonic movement and earthquake,hydrogeological conditions and structural plane.In addition,according to the different lithology of the left bank slope layer,the left bank slope is divided into three sections: H1,H2 and H3,and the main distribution areas of dangerous rock mass are obtained.Secondly,for the confirmed collapse bodies BT1 and BT2,according to the previous fine three-dimensional model,the shape of the slip surface can be geometrically modeled.Based on the multi-angle analysis of the collapse volume,it can be shown that the accuracy of the three profile models of the collapse bodies BT1 and BT2 can meet the requirements of quantitative stability calculation.(2)Based on the analysis of the factors affecting the stability of the left bank slope,it is concluded that the failure boundary of the left bank slope in the gate site area of Bowa Hydropower Station is mainly formed by the combination of the slope surface shape,rock schistose surface,joint surface and other unfavorable structural planes.The complex cutting of joints and cracks makes the slope mainly have three kinds of deformation and failure modes:wedge-shaped deformation and failure mode,sliding deformation and failure mode and falling deformation and failure mode.According to the analysis of the deformation and failure mode mentioned above,the physical and mechanical parameters of rock and soil and the mechanical parameters of structural plane need to be used in the subsequent stability calculation.Based on this,combined with the preliminary data of Bowa Hydropower Station and the inversion analysis of typical sections of damaged rock mass,the recommended values of physical and mechanical parameters of rock mass on the left bank slope of Bowa Hydropower Station are obtained comprehensively.(3)Based on the current slope line of the left bank slope in the gate site area of Bowa Hydropower Station,the overall stability calculation and local stability calculation are carried out.The former mainly uses the rigid limit equilibrium method to analyze the broken-line sliding of the slope,while the latter selects typical blocks on the slope surface for theoretical calculation and three-dimensional block calculation.Finally,the overall stability and local stability of the slope are quantitatively evaluated.(4)Through field investigation and analysis of existing data,the engineering geological conditions of the left bank slope are defined;The development characteristics of two collapses are analyzed.The engineering geological model of the left bank slope is established.The overall stability and local stability of the slope are quantitatively evaluated.Draw the main conclusions and provide the basis for the follow-up governance work.