Rock Mass Quality Classification For Dam Foundation Of Maji Hydroelectric Power Station In Nujiang

Nu River hydropower station located between the Fugong county and Gongshan county in Yunnan Province. The largest height of the arch dams planed to reach 300m and its installed capacity could reach 4200MW.This hydropower station belongs to a large (1) project. So, it would be of great significance to classify reasonably the dam bedrock, select kinds of rocks indexes, rational use of rock and select dam configuration.This power station lied in the valley between Indian Ocean Plate and the Eurasian plate splicing site. It belongs to Gangdise-nyainqentanglha–Gongshan arc wrinkle belt. Although it located in the southwest Yunnan seismic zone, its engineering structure had more stable than others and its seismic activity is weak, only reaching basicⅦintensity degree and corresponding bedrock acceleration rate could reach 112.2 gal.The Mountains height around two sides of the Nu River hit 3000-4000m, there was a complex geological surrounding. Its bed layer belongs to the Gala Bo Carboniferous rock group, whereas the dam site area belongs to the Caledonian granite gneiss rock group, its rock was mainly composed of Granite gneiss. So its structure was mainly metamorphic belt, the dam site area crack developed rapidly and had more strong rhythm. There was obvious crustal stress, so the data of ground stress was higher than two banks of the dam. The largest main stress value was 29Mpa; it had also an effect on dam belt rock.Under the continual action of rock structuring change, such as weathering or unloading, the dam belt rock shaped the existing soft rock belt, so it needs to use kinds of methods to analysis its characteristics, including geophysical prospecting , deformation test, other physical mechanics experiment.This paper is about the research of belt rock surrounding on the foundation of the investigation on scene and in-depth research. Also, the belt rock physical mechanics characteristics were studied. Kinds of single indexes about belt rock qualities were analyzed. Using the indoor and outdoor kinds of rock mass classification methods theory, some suitable standards about Magee hydropower rock mass were designed and further analyzed.The classification methods were put in accordance with engineering rock mass standard and some standard RMR M, RMR. rock mass was carried on comprehensive value using this methods, the standard changed from I to V. this methods had many advantages, first, it was more convenient and rapid to carry on grading the rock mass, secondly, it was suitable to work and carry on reasearch on the scene. it could have a better effect to building dam.