Comprehensive Evaluation And Geological Defects Treatment Of Bedrock Body Quality In Yangfanggou Hydropower Station Along Yalong River

Yangfanggou hydropower station which lies in middle reaches of Yalong river in the Muli county of Liangshan state in Sichuan province is the planning No.5 hydropower station along that reach. The dam area is symmetrical"V"type high mountain valley, where slopes on both sides are steep .While considering slope stability, it calls for special requriment for both roof elevation of rock surface and excavation depth in bedrock body. Therefore, how to choose excavation depth and to analyze and handle geo-problems under effected factors are significant to the construction.Now the construction is at the feasibility study stage. All the investigations and designation works in this paper are synchronous with present construction. Based on present engineering geological problems and investigations and tests, this paper has done profound research on characteristics of rock mass structure and weathering and unloading in the dam area. And chosing of dam base level has been made according to comprehensive evaluation of rock mass quality and stability of both high slope and the dam. Finally, engineering treatment has been made to the deficient bedrock. The main results are as follow:(1)Rock mass structure division plan has been set up through the research of rock mass structure and weathering and unloading factors. Also, a comprehensive zoning of weathering and unloading has been made. From the above analysis, rock mass construction of granite on both banks gradually gets better, even if abrupt changes are within gradual changes. To a certain depth, the degree of decency has little influence on the mass structure. In that situation, faults and its impact zone are to blame for rock mass sturcture changing, which induce relatively weak rock mass structure. (2)A comprehensive classification of rock quality has been made based on Hydro-electric power engineering geological classification of rock and BQ and RMR. The results indicates that rock depth ofâ…¢1 andâ…¡type rock mass in 1995m in shallow than that in 2020m and 2060m, rock depth ofâ…¢1 near spandrel groove at right bank of 2020m is relatively deep within whichâ…¢2 belt exsit, a thicky scale ofâ…¢1 andâ…¢2 rock belt exsit withinâ…¡type rock mass on the left bank downstream.(3)The results from available rock show thatâ…¡type rock of relatively highly anti-slide and anti-deformation can be uesd for dam foundation, whereasâ…¢1 type rock also can be used partly andâ…¢1 type rock can mainly be uesd for spandrel groove whileâ…¢2 type rock can be used partly andâ…£and other type rock must be excavated. Based on these principles, different plan of dam base level can be choosed. The main effected factors of deficient rock are fault structure, gently inclined joint and weathering and loading of rock mass. To ensure stress distribution and stability of high slope at dam abutment after exvacation, accordingly treatments have been raiesd.