| Quality Classification and Stability Assessment of Surrounding Rock Mass in Underground Cavities of Xiluodu HydroelectricPower Station On Jinsha RiverAbstract Rock mass quality classification and stability assessment of underground cavities are two closely correlated aspects, while study on rock mass structure feature is its foundation. Taking underground cavities of Xiluodu Hydroelectric Power Station in the left bank of Jinsha River as an example, the paper bases the study on engineering geological condition of the research region. Making use of abundant field investigation and statistic data, it systematically studies developmental characters of discontinuities in underground cavities and correctly measure off rock mass structure type. Quality classification of surrounding rock mass are carried out according to the classification system in the Hydroelectric Standard of P.R.C(HC) and Geomechanics System(RMR), Q system, which are very popular in the world at present. Additionally, classification system of surrounding rock mass that appeals to this area is explored by properly modi1~uing the system brought forward in Engineering Rock Mass Class qlcatian Standard Stability analysis of the hat under different kinds of rock mass structure is completed and the upper wall stability of the main workshop is studied in the light of SMR system used in slope stability analysis. Subsequently, a geomechanical model of underground cavities is set up and numerical simulation is accomplished applying 2D-FEM program. It focuses on whole stability of underground cavities under gravity and tectonic stress, the effect of mechanical parameters, construction order and interlayer shearing belts. Finally, synthetic discrimination of surrounding rock mass quality is completed and corresponding timbering measure is put forward, which is of great importance to design and construction of the cavities.
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