| Stability of high rock slopes has become the key engineering geological problem in the construction of hydropower station in mountainous area.An excellent example is Rumei hydropower station on Lancang River,which is located in Tibet,China.It is the fifth-level power station among the seven cascades planned for the river basin below Changdu City.The adjacent upper and lower steps are Banda Hydropower Station and Bangduo Hydropower Station.The height of cutting slope in the right bank of Rumei hydropower station reaches 665 meters,with a total of more than 1000 meters of the natural slope,and the permanent slope above the dam top is up to 350 meters.The geological condition is complicated in the study area: well developed fractures,strong weathering and unloading,numerous rock mass with fragmented and loosen surface.Based on methods such as geological survey,data collection,laboratory and in situ test and mathematical statistics,a systematic study is carried out to analyze the stability of the high slope of the right bank abutment of Rumei hydropower station..The main research results obtained are as follows:(1)Dincontinuity development characteristic is studied using the methods of geological survey,statistical analysis,interpretating the digital image of the prospecting adits.The fractures developed in the slope can be categorized into deterministic and random fractures.The deterministic one mainly involves three types: surface cracks,faulty belts and small faults exposed by adit.Additionally,the main three sets of random fractures including two sets with high-angle and the other one set with low-angle.Then,the grading standard of the discontinuity of Rumei Hydropower Station is established,considering the situation of the project.Reusults show that the right bank slope mainly develops fractures of grades III,IV and V.(2)Physical and mechanical parameters of the rock,rock mass and discontinuity were obatained by statistical analysis,estimation based on the Heok-Brown criterion,on the basis of data obtained in laboratory test,in situ rock mass shear test.(3)Indicator of RBI(the rock blocky index)was used to classify the rock mass structure.Firstly,RBI investigation was carried out in the representative boreholes and prospecting adits.Then,rock mass structure was classified.The results show that very blocky and mosaic structures are the main rock mass structure in the study area.(4)Based on the detailed geological survey of PD6,PDZ08 and PDZ10,combinedwith laboratory test and field acoustic wave test,the rock mass quality classification of slope is carried out using BQ method,RMR method and CSMR method respectively.The classification results show that quality of the slope rock mass is mainly grade III and grade IV.The correlation between BQ method and CSMR method is significant.(5)The kinematics analysis was used to study the stability and failure mode of rock slopes by considering connectivity rates of fractures,based on the geological condition in PD6,PD2,PDZ10 and PDZ42.The results show that in the region of PD6,the main failure modes of the slopes are wedge and toppling failures when the connectivity rate of fractures is larger than 45%,and the main failure mode of the slopes is toppling failure when the connectivity rate of fractures is smaller than 45%;for the rock slopes in the region of PD2,the main failure mode of the slopes is toppling failure when the connectivity rate of fractures is larger than 30%,and the slopes are stable when the connectivity rate of fractures is smaller than 30%;for the rock slopes in the region of PD10,the main failure mode of the slopes is toppling failure when the connectivity rates of fractures are 40%,50%,70%,and 100%,and the slopes are stable when the connectivity rates of fractures are of other values;for the rock slopes in the region of PD42,the main failure mode of the slopes is toppling failure when the connectivity rate of fractures is larger than 40%,and the slopes are stable when the connectivity rates of fractures are of other values.(6)Failure modes of the cutting slope were proposed after geological analysis and the kinematics analysis,based on survey of the exsiting failure phenomenon in the slope and prospecting adits.Toppling and sliding-cracking will be the main failure modes in the cutting slope.(7)Slope Stability Probability Classification method that considers the failure mode of rock slope was adopted to evaluate the stability of high-steep rock slopes in Rumei hydropower station.Hydropower-SSPC based on prospecting adits was also proposed,the failure modes of the rock slopes were classified into tectonic controlling and non-tectonic controlling types.The results show: the failure mode of the slopes after excavating is mainly controlled by the topping failure along steep inclination fractures,and there is no non-tectonic controlling failure mode.The obtained results are consistent with those obtained from the kinematics analysis and the numerical simulation.The main innovation of this dissertation is as follows:(1)The SSPC method considering failure mode was used to the stability evaluationof high steep slope in hydropower engineering.The Hrdropower-SSPC evaluation method based on adit geological data is established.(2)The selection and determination of rock compressive strength,weathering degree and other evaluation indexes of original SSPC method were improved.According to the test results of adit acoustic wave,the weathering degree of slope rock mass is quantitatively evaluated.The formula of critical slope height is optimized and applied to the stability evaluation of right bank abutment slope of Rumei power station.(3)Mathematical relationship between the GSI and seismic velocity of slope rock mass was obtained by back analysis based on in situ deformation test sonic wave testing,which provide a new mehod getting the GSI in the evaluation. |
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