Evaluation On The Rock Mass Quality Of Dam Site Area In Yebatan Hydropower Station On The Upper Reaches Of Jinsha River

The hydropower station in southwest of China is distributed steply on Dadu River, Yalong River, Jinsha River, Lancang River and Nujiang River.The merit of the rock mass quality mass plays a vital role on the construction of hydropower station. not only does it affect the choice of the dam site and also control the depth of slope excavation. It not only affect the selection of dam site, also affect the excavation depth of slope. Yebatan hydropower station is located in the boder of Baiyu county of Sichuan province and Changdu prefecture of Tibet autonomous region. The dam site area has majestic mountains, steep terrain, narrow valley, high shore slope, forming a deep mountain " V " Valley. Therefore, The complex engineering geology condition causes the rock mass quality exist difference.This paper takes the rock of dam site area in Yebatan hydropower station as research object. Based on the statistical analysis of field data, and combined with the indoor and outdoor experimental data, by adopting the combination of qualitative and quantitative way of thinking to determine the degree of weathering and unloading of the rock. Then on the basis of weathering unloading line was carried out the rock mass quality classification, at the same time find out the cause of the differences. Finally, it is concluded the rock mass classification system and the results. The main researches are as follows:(1)Analyzing the engineering geological characteristics of Ⅰ, Ⅱ, Ⅲ, Ⅳ, Ⅴ level structure on the advantage of structural plane, the angle of structural plane, the filling type of structure surface and the state of groundwater through the actual measure data of 27 adits.(2)Using velocity ratio, the number of joint in 5m adit and uniaxial compressive strength to differentiate the doundaries of upper weak-weathered rock and under weak-weathered rock. And combines with the qualitative boundaries, it concludes the final rock weathering boundaries.(3)Using the number of open joint in 5m adit and longitudinal wave velocity to differentiate the doundaries of strong unloading, weak unloading and deep unloading. And combines with the qualitative boundaries, it concludes the final rock unloading boundaries.(4)Counting the strength of rock, spacing of joint, coefficient of rock, and RQD to obtain the preliminary classification of rock mass of dam site area.(5)Using BQ and RMR to classify the rock mass quality based on the final weathering and unloading line. It analyses the correlation, consistency and coincidence rate of the classification result, and finds out the reason why there are differences in the classification result.(6)According to the analysis of the reason determines the parameters that need to be revised. Combining with the actual engineering geological conditions of Yebatan hydropower station, it revises the corresponding parameter’s score values and modifies the correspondence between the values of BQ and RMR and rock level. Then it puts forward the corresponding revised scheme and concludes the revised BQ and correction RMR classification result. At last, it analyses the coincidence rate of the revised classification result.(7)According to the revised BQ and RMR scheme, it puts forward a suitable rock mass quality classification system for Yebatan hydropower station. Combining the revised BQ, RMR classification result and water resources and hydropower dam foundation rock mass engineering specification, this paper obtains the comprehensive classification result of the dam site area finally. It is concluded the mechanics parameters value of the different level of rock mass and the rock mass structure. And analyzes and the relationship between the mechanical parameters and the rock mass quality classification result.