Rock Mass Quality Classification And Engineering Effect Study Of Complicated Rock Mass At The Right Dam Foundation Of Nuozadu Hydraulic-Power Station In Lancang River

Nuozadu hydraulic-power station will be built in Lantsang river in Yunnan province, has a oversize hydraulic power project, its highest height of the design dam achieve 260 meter, and its installed capacity arrive 5,600,000 kilowatt. Past investigation found the rock in the right dam foundation composing of granite(γ₄³ï½žÎ³₅¹) in dyas- trias,which has a very complicated mechanical environment. The complicated phenomenon is as follows: tectonism, alteration, rock mass demobilize, rock mass stress release and other factors. Because of this several weakness rock zones and a loosen rock mass zone are develop in the right dam foundation. Hereby, a study on the mechanical genesis ,rock mass quality and engineering effect of the complicated rock mass is very important. Base on site investigation and abundant past achievement, we carefully studied it and draw some conclusions.The mechanical genesis of the complicated rock mass is because several times of tectonism in pro-period made the structure of rock mass in the right dam foundation damaged seriously and rock mass alteration made its mechanical character more anisotropy. After that the fractures in the right dam foundation slope were stretched at the beginning of the Quaternary Period because in the period Yakouhoushan mountain quaquaversal dome was blowups quickly. At the same time, the valley trenching of Lancang River reach to 800-1000 meter in altitude at the right bank in Nuozadu dam site. This two reason accelerated the groundwater infiltration in the right bank slope. So, the weathering agency could have invaded deeply in the right bank slope. After long-term synthetic action of these factors, the complicated rock mass in the right dam foundation come into being.The adjoining rock engineering geological classification of water -conservancy and hydraulic-power project reconnaissance code (GB50287-99), geomechanic system (Bieniawski,1973), rock mass quality index Z (Xiaowang ,1995), artificial neural network and field classification were used in the rock mass quality classification. A evaluate system relative to the rock mass mechanism of the complicated rock mass was achieved finally. The result of rock mass classification reflected that the rock mass quality is relative compactly to the mechanical genesis of the complicated rock mass.In the last part of the thesis a study of engineering effect about the complicated rock mass was done base on a numerical simulation and the engineering geological condition in the dam site. Numerical simulation result reflect several disciplinarian of stress-distortion action in the right bank slope. Firstly, today's right bank stress field mainly is grave stress field. Secondly, because of strong stress release in the flat of the slope, there has a high grads zone. After the engineering slope wasdug, several small plastic zone the designed rock-fill dam will coming in the temporary slope, because rock-fill dam change the stress field on a small degree. But a gravity dam will arouse a great area of plastic zone in the permanent slope, which will bring a stability problem.After detail and depth study ,the rock-fill dam project is more compatible of the engineering geology condition in Nuozadu hydraulic-power station's dam site.