The construction and excavation process of underground powerhouse of Fuziling Pumped Storage Hydropower Station are simulated by three-dimensional fast Lagrangian method(FLAC3D). The pattern of deformation caused by excavation and stress state in surrounding rock mass are studied. The stabilities of surrounding rock mass of the powerhouse and the high slope of the surge chamber are analyzed. The bolting supports are performed on the region of the underground powerhouse caverns; and the mechanical properties of the reinforced surrounding rock mass are analyzed. By using the Ubiquitous model of FLAC3D program

we introduce a major joint cranny to surrounding rock mass and analyze the excavation deformation and the integral stability of the underground powerhouse caverns. Compared the numerical simulation results with no joint cranny around the surrounding rock mass

the effects of joint cranny on the stability of surrounding rock mass are evaluated comprehensively.