Study On The Slope Stability Prediction Of The Reservoir Bank Of The Zhongbo Hydropower Station In Tibet

Proposed ZhongBo hydropower station is located in the eastern qinghai-tibetPlateau in China jade living in prosperous ZuoGong county area downstream of theriver. ZhongBo reservoir is a typical valley reservoir which has complex geologicalconditions.All kinds of the colluvial deposit and diluvium, landslide debris, debrisorder of merit of quaternary covering the development. For a few large fracture alongthe jade living distribution, local rock band slope integrity is poor.After thecompletion of the reservoir,the geological conditions of reservoir bank will producesharp change.The reduce of the strength of rock mass, artificial lake wave erosionscour and additional dynamic water pressure caused by water level fluctuation andthere may be a large dump deformation that will make the slope stability problembecoming more prominent.So,bank slope deformation failure mode and inducingfactors is analyzed, and the rock band slope and soil bank comprehensive evaluationof the stability of the reservoir tank is of huge significance.ZhongBo reservoir area in general is given priority to in canyon section, There isjust about4km long wide valley section near the GuoLuQu.The rock is mainly marble,limestone, slate, sandstone and siltstone. Article divide the hub area into three factorssuch as head area of the reservoir,middle part of the reservoir,tail area of the reservoirand nine smaller section on the basis of field geological investigation, considering theexisting topography and geomorphology, strata lithology and its influence on hubarea.so it can give a full view of basic geological characteristics of the hub area。Thelope stability evaluation also according to the division subsequently,so the results canbe compared clearly.Reservoir bank soil slope stability evaluation take slope geologic analogymethod of the stable slope forms and angle(Two stage method).The final width of bank collapse after water storage is calculated based on the stable slope angle ofdifferent height bank.The focus of this method is the getting of the overwater stableslope angle and the underwaterstable slope angle of .Bank collapse predictioncalculations use the composite value of water stable slope angle and the underwaterstable slope angle of the investigation field and similar reservoir soil bank slopevalue which has run for years.Debris paper to distinguish the different genetic types ofsoil slopes, and according to its specific composition further specialization, based onthe above principle, the statistics of medium wave reservoir bank collapse predictionof all kinds of soil bank characteristic value, the value is high credibility, and inconformity with the field geological macroscopic judgment.The construction of bank rock slope stability evaluation system mainly use thefuzzy comprehensive evaluation method. The method to a affected by many factorssuch as geological disaster risk assessment, and has a strong fuzziness, advantage isvery obvious.The evaluation factor set,weight set and the evaluation level isdetermined.On the basis of predecessors’ experience, analogy and other evaluationsystem and the specific situation in the study area,the single factor value isdetermined.In consideration of the complex indicators and the difficult to directlycompare the importance of the risk, Each index weight is determined using thecombination of qualitative and quantitative comprehensive analysis.Specifically, firstof all, is to analyze the basic geological factors affecting the stability of rock slope,namely geological lithology, geological structure conditions, geological conditions,topography and river bank deformation and failure conditions, choosing the aboveseveral factors as the basis of stability evaluation.To determine factors influence thestability evaluation index, such as human activities, factors such as earthquakeintensity, rainfall and reservoir level fluctuation, to determine evaluation indexweights value distribution, and finally set up the intact rock slope stability evaluationsystem.In accordance with the uniform evaluation criteria, to evaluate each segmentaccording to the geotechnical slope one by one, and then for each period ofcomprehensive evaluation, the final overall evaluation in the study area.The author use the segmented evaluation method.Divide the study area into threepart,that is,the head area of the reservoir,middle part of the reservoir,tail area of thereservoir and nine smaller section considering the landform, stratum lithology and itsinfluence on hub area construction.The evaluation factors set conclude the formation lithology,geological structure,geological structure type, the status qua of the bank slope deformation and destruction, river erosion, rainfall, earthquake and water level fluctuation.The evaluation systemdivide the rock slope stability into four levels: better, good, poor, poorer.According to the results of the evaluation scheme,the soil slope in the head areaof reservoir has a better stability, individual some deposit (the downstream of the damsite) have a pooer stability;the soil slope in the middle area of reservoir has a betterstability except the talus and the soil slope between the downstream dam site and theZhangHongQu has a a bit poorer stability,the slope in poor stability is very little; thesoil slope in the tail area of reservoir has a better stability,some scree, artificialabandon slag deposit and the first period in ice water has a poor stability and the largenumber of soil bank in some tributary has a poor or poorer stability.Rock band slopeis stability generally good or better, mainly is good. The first section and the thirdsection of the head area of reservoir is good. The second section of the stability isbetter.The rock slope of the middle area of reservoir has a good entirety stability andthe second and the third period of it are best relatively and the area where has a poorstability is very little, less than3%.The rock slope of the tail area of reservoir has agood entirety stability and the left bank stability is better than the right. Stabilityevaluation result is tally with the qualitative analysis in general.