Abstract: Based on an analysis of engineering geology conditions of Pengshui Underground Plant, the 3-dimensional distinct element numerical model is established. The excavation and reinforced process of underground powerhouse of Pengshui project are analyzed by using 3DEC. The pattern of deformation, stresses state, distribution of plastic regions caused by excavation and influence factors of cavern surrounding rock are studied. Several conclusions are drawn: the whole stability of excavated and reinforced surrounding rock is good according to this paper’s calculation conditions; the displacement of upstream and downstream walls are about 15~35 mm under excavation and control of discontinuous combination; the mostly deformation of cavern walls are completed from excavated to subsequent 2~3 excavation steps. the excavation phases from 223.0 m to 201.0 m are important to stability of cavern walls; the characteristics of lay, interlay and continuous joints and the blocks location cut by discontinuous have significant effect on surrounding rock stability, but local shale deformation and geostress have little influence on the stability of cavern walls.

Key words: Pengshui Underground Power Plant, cavern surrounding rocks, analysis on stability;3DEC