Study Of Foundation Rock Mass Quality Checking On The Right Bank Of Jinping I Hydropower Station

Jinping I Hydropower Station which is under construction is located on the west side of Jinping grand river bend in the middle of Yalong river. Type of the dam is Double-curvature arch dam, the designed height is 305m, reservoir storage is about 77.6×108 m3, and equipped capacitor is 3600MW.In this dissertation, the study subject is the foundation rock mass on the right bank 1885 ~ 1700m elevation of JinpingⅠHydropower Station. Base on the investigation of the characteristics of rock mass structure as well as engineering geological conditions, the characteristics of rock mass quality has been analyzed. Using the geological analysis, , engineering statistical method and fuzzy comprehensive evaluation method, a more complete analysis of foundation rock mass quality characteristics on the right bank has been done and the corresponding support recommendations for distinguished geological defects are given; the characteristics of the rock mass structure, acoustic wave, deformation modulus and their associated relationship have been determined by research, the difference of rock mass quality distribution between now and before has been analyzed, and the rock mass quality has been reevaluated. At the same the effect of blasting excavation on rock mass quality also has been studied. Details and results are as follows:1)Through on-site survey, the characteristics of the rock mass structure on the right bank of 1885 ~ 1700m elevation have been studied.2)According to the single factor and multi-factor classification standards in Jinping rock mass quality classification, combining acoustic wave and deformation modulus data, the characteristics of acoustic wave velocity and deformation modulus have been reviewed, and their associated relationship and the difference from before have been analyzed.3)Based on lithological composition, rock structure, weathering and unloading conditions and acoustic test data, the exposed geological defects on the excavation foundation rock which the engineering geological characteristics are poor has been depicted in a separate. Combining the rock mass quality classification standard, they have been classified and the corresponded treatment recommendations have been given according to the principles of foundation rock mass treatments.4)By the use of the idea of combining qualitative and quantitative grading, the rock mass quality on the bench has been reevaluated by the fuzzy comprehensive evaluation method. In order to compensate the deficiency of using the excavation bench as evaluating unit, combining the characteristic of rock structure, acoustic wave velocity, geological defects, the distribution characteristic of rock mass quality have been checked.5)Combining the long term observational holes'acoustic wave velocity data and monitoring data, the impact of blasting excavation on the rock relaxation have been analyzed. Generally speaking, the blasting relaxation depth is between 0.8m and 2.4m, however, the difference of stress relaxation depth is bigger.Through the above analysis, after the excavation of foundation on the right bank, rock mass in general agreed with the earlier stage's, foundation conditions agreed with the results and understanding of preliminary investigation.Ⅱ,Ⅲ2,Ⅴ1 level rock compared with earlier stage's, the rate is less than 1.0%,Ⅲ1 level rock area decreased by about 3.7%,Ⅳ1 increased the level of rock about 5.2%. Geological defects is the main factors that affect the quality of the right bank of the dam foundation rock mass, the need for separate treatment are as follows: f13 and f14 fault zone and their effects'areas, the weak to strongly weathered, the weak levelⅢ2 unloading rock, strongly weathered green schist; Other weak weathering Green schist need to be shallow cleaned before Dam concrete pouring...