Abstract：Modeling the effect of blasting-caused damage，anisotropy of rock masses and excavation sequence on deformational behaviour and stability of large-scale underground houses is important in the design and information-oriented construction of the pumped storage power plant. A powerful three-dimensional numerical method that can be applied for that purpose is presented in this paper. The influence of damage caused by blasting and discontinuities in rock masses on the stability of houses is considered by reducing the deformation coefficient E of the surrounding rock masses based on the relation to seismic velocity Vp. Numerical simulations of the underground excavation of the Omaru Pumping-up Hydroelectric Power Plant，which is one of the big construction projects in Kyushu island，Japan，were carried out to evaluate the influence of damage caused by blasting and reinforcement by rock bolts on the stability of powerhouses. The damaged range and mechanical properties of rock masses near to the walls of houses are determined by using the back analysis approach in which three lines of the measurement results during the arch part excavation process were used to verify the simulations. Finally，applying the improved model and properties of rocks，the house stability and reinforcement effect of the preliminarily designed support system are also estimated for the safety in the coming several bench excavation process.
