Study On The Deformation Failure Model And Stability Of The Abutment Of Danba Hydroelectric Station In Dadu River

The Danba hydropower station installs capacity of 1196.6MW in Dadu River,which adopts the gravel soil core wall rockfill dam, the dam height of 36 m. The slope of dam shoulder area is high and steep, which is influenced by different periods,different scales and the internal and external force, the rock mass structure is complex,and the slope problem is more prominent. It is an important factor to control the stability of the slope by the development of the joint, small fault and crush zone in the region, and the surface of the slope is accompanied by a strong weathering unloading effect, it has great influence on the stability of the slope, which is related to the success or failure of the project construction, and it will play an important role in the feasibility, safety and economy of the whole project, and which has a great extent affect on the construction of the investment and benefits. Therefore, it is necessary to analyze the stability of the slope stability of the dam shoulder.This paper relies on the thematic study about slope stability of dam area of Danba hydropower station in Dadu River. On the basis of a comprehensive understanding of the stability of rock slope, through a detailed study about the dam engineering geological conditions, slope structure, weathering and unloading features,rock mass quality and slope failure type and boundary conditions, then the stability of the dam abutment slope is studied as the core. through a variety of methods to obtain rock mechanical parameters, than the stability of natural slope and the stability of the slope after excavation are analyzed and evaluated systematically by qualitative analyses and calculations. The specific research contents and results are as follows:(1) Through the investigation and analysis of the geological environment of the slope, The abutment slope mainly exposed fifth rock group of stratigraphic Silurian Maoxian group and first rock group of Weiguan a set of strata. Lithology takes quartz rock with felsic granulites, small two sillmanite garnet schist, dolomitic coarse marble,felsic granulites and cloud quartz schist as the main. The non regional faults(I, II) of the slope of the dam shoulder are through, the secondary small faults of the dew, thecrushing and crushing zone, and the joint and fissure(fracture zone) have a controlling effect on the stability of the slope, weak weathering and unloading with horizontal depth 30~50m, the slope structure of abutment area is weakly weathered block structure ~ lower layer structure.(2) Study on rock mass structure characteristics of dam shoulder slope: including the distribution law, the development density, the surface characteristic, the continuous characteristic and the shape of the space combination. The main structural plane of the dam abutment slope is the small fault and compresso-crushed zone of III,IV grade. The structural plane of III stage is mainly based on NNW, The development of the structure of grade IV is less, and the distribution of NNW and near EW is the main one, the structure of V level is mainly of joint and crack. Because of the topography, rock group different dam slope area, the development characteristics of rock joints and fractures are different, But it is major in the middle steep and high-angle angle, which has a high proportion of joint development. Through a systematic research on the characters of rock mass structure and the size of the system,it provides a basis for selection of dam site rock mass quality classification and rock mass mechanics parameters.(3) Application of quality classification of slope rock mass, on the basis of the qualitative classification of slope rock mass quality classification, the SMR classification method and the modified CSMR classification method, the quality classification of the slope is carried out. The main rock mass quality grade of dam abutment slope is III1 and III2, of the 2 kinds of rock mass, The IV rock mass is mainly in the soft stratum(rock vein development, fault, crush zone) and the weak weathered rock mass section of the slope surface. According to the slope rock mass quality classification, the rock mass mechanical parameters are determined according to the rock mass quality classification in the reference standard, combined with the engineering geological analogy method, field test and laboratory test data.(4) The slope of the dam abutment is a layered structure~block structure, the deformation and failure mode of the slope is determined by the combination of joint and fracture development. By cutting the structure of different directions, the formation of many blocks, individual development into dangerous rock. Deep deformation is mainly determined by the combination of unloading fracture, small fault and joint density zone. Affected by the surface control structure of outside slope,on the surface of left bank slope, deformation failure mode is mainly plane slip failureand collapse type failure, and the surface deformation and failure mode is mainly for wedge sliding and falling failure, which forms rock cavity concave landform.(5) By using geological analysis method, rigid body limit equilibrium method and finite difference method, the analysis and evaluation of the slope stability. The analysis shows that the overall stability of the natural slope is good, mainly for the rock stability of strong unloading zone, the steady state is up to standard in various working conditions, the stability coefficient is greater than 1.05, but for the individual block, at the state of the earthquake and rainstorm conditions, it is in the limit equilibrium, there is instability risk. The engineering slope is in the basic steady state under the natural condition, in the limit equilibrium state under earthquake and heavy rain condition, there is instability risk. It is mainly due to the shear outlet of the leading edge induced by excavation, the construction of the opening line of the slope above the appropriate system to anchor, when the construction is required, the slope of the opening line above is required to be anchored properly and systematically.