Study On The Storage Stability Of The Right Bank Slope At The Middle Dam Site Of Banda Hydropower Station

Slope stability has always been the most concerned problem in water conservancy and hydropower projects for a long time.In the operation or storage stage of the reservoir,the change of water level has a crucial effect on the stability of the slope,so it can be said that the change of water level plays a controlling role on the stability of the bank slope.The middle dam site is located at about 0.6km in the upper reaches of siruhe river,and the dam site area has a straight river course.Moreover,during the dry water period of the river,the elevation of the river at the dam site is 2892 m,the width of the river surface is 40 m ? 90 m,the water depth is generally,and the general range is 5m ? 10 m.The water level after the normal impound is 3054 m,and the river's width is 400 m ? 440 m.Through the engineering geological conditions of the right bank of dam site,rock mass structural plane development characteristics,rock mass quality classification,and through the test of all kinds of physical and mechanical properties of rock mass parameters,etc,on the basis of investigation,using the numerical simulation of natural conditions and water storage condition of slope seepage field,stress field change,to analyze the slope stability.The research results are mainly as follows:(1)The primary structural plane,structural plane and shallow structural plane of the right bank slope at the middle dam site are well developed,which makes the rock mass structure of the right bank slope at the middle dam site more complex.At the same time,according to the field geological survey,the study area is classified according to the rock mass structure,rock mass structural plane and rock mass quality by referring to relevant specifications.Cataclastic-block-cataclastic structure;Mosaic-sub-block structure;Submassive-massive structure;Rock mass structural plane in the study area is divided into ?,?,? level,and further analysis on the surface of the structure of three kinds of development;Study the slope rock mass quality evaluation according to the BQ method,quality of rock mass can be divided into four categories: ?,? respectively,?,?,including strong weathering of rock mass and strong alteration rock belongs to the ? class.(2)According to the overall weathering characteristics of each adit,it can be found that: most of the rock mass in the study area has strong weathering characteristics,and there are some strong weathering sections,but the thickness of the middle elevation and high elevation of the weak upper weathering zone are all greater than 100m;In the direction of elevation,the weathering degree of rock mass and elevation increase in the same direction,with the increase of the distance from the slope surface,the weathering degree decreases in the horizontal direction.According to the development of unloading fissure in each adit,it can be divided into strong unloading,weak unloading and ununloading.(3)The Seep module in the numerical simulation Geo Studio was used to calculate the changes of the infiltration lines and pore water pressure of the three sections at different water storage speeds at different heights.The results show that the infiltration line and pore water pressure gauge in the slope show a certain hysteresis.In addition,the pore water pressure near the slope surface of the slope body,there is a negative pressure,the direction of the front edge of the slope body.(4)The Sigma module in the finite element software Geo Studio was used to analyze the change characteristics of seepage field and stress field under the rising water level of the reservoir.The results show that due to the rise of water level,the stress stress field changes to different degrees,the maximum principal stress,minimum principal stress and shear stress isoline distribution map become denser,and the values become larger.(5)According to the potential sliding surface that may exist in the failure mode of slope failure,the rigid body limit equilibrium method is used to calculate the potential sliding surface.Under the conditions of different elevation and different water storage speed,the stability coefficient generally shows a decrease and then a rise.At the same time,in the natural state,the potential sliding surface is in a stable or basically stable state.Due to the rise of water level,the stability coefficient of some potential sliding surface is reduced to different degrees,which may lead to local instability.(6)Using the FLAC3D three-dimensional numerical simulation method,analysis the global stability of the slope under the condition of natural and water storage,the natural condition,when calculating the water storage condition of the slope of maximum principal stress and minimum principal stress,shear strain increment and displacement field of the results showed that the maximum principal stress value increases,the minimum principal stress in the slope loose cataclastic rock mass characterized by tensile stress,the displacement value of expanded several times,at the same time of B-B 'section shear strain increment has almost completed,have occurred the possibility of instability.