Study On The Ultimate Capacity Of Arch Dam And Stability Evaluation Of The Abutment Slope Of Dagangshan Hydropower Station

With the vigorous development of water resources in China,a large number of hydropower stations are being built or have been put into use in Southwest China.These hydropower stations are accompanied by tall arch dams and high-steep rock slopes,and the geological conditions in the dam site are harsh.So,the stability of arch dam and slope of hydropower station becomes particularly prominent.Once disasters such as dam-collapse and landslides occur,not only the toppling damage of arch dam occurs,the safety of the lives and the property of the downstream people is also a huge threat.It is very urgent and necessary to study the extreme carriers of arch dam and the stability of the abutment slope,and which has important engineering and practical significance.In this paper,Dagangshan Hydropower Station is taken as the project background,and the ultimate bearing capacity of arch dam and the stability of the shoulder slope are studied through on-site monitoring,theoretical analysis and numerical calculations.The main research contents and results of this paper are as follows:1.The distribution characteristics of the natural geo-stress in dam site area and the failure mode of the slope rock mass after excavation are analyzed by the field experiment of natural geostress in dam site area.It is found that the ground stress in the dam site area belongs to the medium-high ground stress state.The distribution law of radial displacement and tangential displacement of arch dam in different dam sections and different elevations is analyzed by the field deformation monitoring.It is found that the radial displacement of the arch dam reaches the maximum at the dam axis during the impoundment period,and the tangential displacement reaches the maximum at 1/4 of the left and right sides of the arch dam.2.A three-dimensional numerical calculation model considering joints and shear holes of Dagangshan hydropower station is established.The stress and displacement distribution of arch dam and slope under different water levels are studied.It is found that the highly stressed zone area of the arch dam moves from the toe area to the heel area with the decrease of water levels.The ultimate bearing capacity and failure mode of arch dam are analyzed by the overload method,the strength reserve method and the cusp catastrophe theory.It is found that the left and right arch ends of the dam crest elevation and the left and right sides of the dam heel are the first to crack under different overload or load reduction coefficients.The vulnerable area of the arch dam is delineated from a macro perspective.According to the numerical calculation results,the numerical calculation model of triaxial test in the vulnerable area of arch dam and dam foundation is constructed by PFC3D discrete element software.The mechanical characteristics and failure modes of arch dam and slope are studied from microscopic angle.3.The dam abutment position is defined as the vulnerable area based on the previous analysis,and the comprehensive evaluation index system of abutment slope stability is constructed by considering the various affecting factors.An abutment slope stability evaluation method based on VIKOR-binary semantics is proposed.The development of visual execution window and operation software for comprehensive evaluation model is realized based on Python software.The stability evaluation system of the abutment slope is applied to different hydropower stations.It is found that the calculation results of the rock slope stability prediction model proposed in this paper are more accurate than those obtained by other evaluation methods,and which are more consistent with the actual engineering situation.The research results of this paper have certain reference significance and application value for the safe operation of hydropower station and the stability analysis of arch dam and high rock slope.