Study On The Rock Mass Structure Characteristics And Stability Of Left Abutment Slope Of Shaping ? Hydropower Station

Located in Ebian County and Jinkouhe District,Leshan City,Sichuan Province,the proposed Dadu River shaping I hydropower station is located in the middle of the middle reaches of Dadu River,with a total installed capacity of 360MW and a dam type of concrete gate dam,with a maximum dam height of 63m.Shaping cascade hydropower station is the 20th of 22 planning cascade in the middle reaches of Dadu River.The regional fault F₁₀ is developed in the dam site area,which runs through the upstream and downstream of the dam site.Its strike is roughly the same as the river flow direction,and it tends to the inner side of the mountain on the left bank,with an inclination of 60o?80o.Affected by F₁₀ fault,the left bank has a high degree of weathering,and the rock mass is relatively broken.There are deformation bodies in the left bank dam abutment area.The occurrence of rock mass changes greatly.There are problems of dam abutment leakage and slope stability,which are directly related to the safety of water storage during the construction period and operation period of the project.Therefore,it is very important to analyze and study the rock mass structure and stability of the left bank dam abutment slope.In this paper,the left bank slope of Jinkouhe dam site,the recommended dam site of Dadu River shaping I Hydropower Station,is taken as the research object.After consulting the previous relevant research results,the field geological survey of the dam site area is carried out,and the relevant indoor tests are carried out,the engineering geological conditions,the structural characteristics of the slope rock mass,the engineering characteristics of the regional fracture structural plane,and the strength of the rock mass and structural plane are referred Number,rock mass quality classification,slope deformation and stability are studied systematically.According to the development characteristics,engineering properties and structural influence of the F₁₀fault?i-level structural plane?,which has a great influence on the left bank slope in the dam site area,combined with the structural quality classification of the slope rock mass of the left bank abutment slope and the corresponding field and indoor test parameters,the geological analysis method,the rigid limit equilibrium method and the numerical simulation analysis method are used to analyze the natural slope of the left bank and the excavated natural slope.The deformation characteristics of the model are analyzed and the stability evaluation is given.Through systematic analysis and research,this paper mainly obtains the following basic understanding and conclusions:?1?The structural conditions of the area where the first-class hydropower station is located are complex,and the regional structural stability is classified as poor.The basic seismic intensity of the project area is VII.There are vein intrusions near the river bed on the left bank,which are mainly altered diabase and granite porphyry.According to the survey,the regional fault F₁₀ is located in the dam site area,and the stratum has been metamorphosed in varying degrees through multiple geological tectonic processes.The stratum dip angle is relatively steep.The occurrence of dolomite stratum on the left bank of the dam site is:N20°?40°E NW?50°?70°.The unloading and surface weathering of slope rock mass are relatively strong,and the surface rock mass is relatively broken.Influenced by the steep structural plane,the groundwater in the slope area of the left bank abutment is deeply buried,and the rainfall in rainy season is quickly lost,which has little impact on the slope.?2?According to the field survey and indoor statistical analysis,there are grade I?V structural planes on the left bank abutment slope,among which the regional major fault F₁₀?grade I structural plane?has a great influence on the structure and stability of the left bank,with the occurrence of N0°?40°E NW?60°?80°,and no outcrop on the surface.The main strike of the slope fault is NNE,followed by NE and NNW,and the steepest dip angle is the most developed,while the gentle dip angle is relatively undeveloped.The fault is mainly compressive,mainly rock debris type.In terms of the occurrence direction of the joint fissures on the abutment slope,the dominant directions on the left bank are mainly NNW and NNE directions,which are parallel development and intermittent extension,and the steep dip structural plane has the absolute advantage,followed by the slow dip structural plane.?3?The qualitative and quantitative methods are used to evaluate the rock mass quality of the slope.The results show that the quality of rock mass of the left bank abutment slope is in the order of V,IV and III rock mass,mainly V rock mass,the overall rock mass is relatively broken,most of which are distributed in the fault fracture zone developed by F₁₀ fault?I structural plane?and the surrounding rock area affected by the strong weathering unloading on the slope surface and the deep slope;IV rock mass is mainly crushed by fault compression Zone,vein development,water level and other leading factors are some of the weakly weathered rock mass;the proportion of class III rock mass is the least,mainly the slightly weathered rock mass with better integrity in the depth of the slope.At the same time,according to the quality classification of slope rock mass,with reference to the recommended values of rock mass parameters in the specifications,combined with the engineering geological analogy method,indoor rock mass mechanical experiment and field test data,the rock mass mechanical parameters are determined comprehensively.At the same time,the mechanical properties of the fault zone structure were tested in the field and indoor,and the results of the physical tests on F₁₀ fault were obtained,which can provide reference for the analysis of slope stability system and the actual slope design.?4?By using geological analysis,rigid limit equilibrium method and numerical simulation analysis method,the stability of left bank abutment slope is systematically analyzed and evaluated in strict accordance with the construction process.The analysis shows that the saturation line in the left bank abutment slope gradually rises with the construction excavation and later water storage operation,and the influence depth of water storage on the slope body increases;the settlement of the railway subgrade shows a trend of small inside and large outside;After the completion of the first level excavation,the stability of the left bank slope as a whole and the foundation cover boundary is relatively stable,the local stability of the railway subgrade slope is relatively low,and part of the calculation conditions are in an unstable state,so the railway subgrade slope needs timely support.using geological analysis,rigid limit equilibrium method and numerical simulation analysis method,the stability of left bank abutment slope is systematically analyzed and evaluated in strict accordance with the construction process.The analysis shows that the saturation line in the left bank abutment slope gradually rises with the construction excavation and later water storage operation,and the influence depth of water storage on the slope body increases;the settlement of the railway subgrade shows a trend of small inside and large outside;After the first level excavation,the stability of the left bank slope as a whole and the foundation cover boundary is relatively stable,the local stability of the railway subgrade slope is relatively low,and part of the calculation conditions are in an unstable state,so the railway subgrade slope needs timely support.