Abstract：Numerical simulation is one of the main approaches to deal with such problems as reasonable layout and construction of underground powerhouse. The computer codes for fast Lagrangian analysis of continua，FLAC and FLAC3D，with the explicit finite difference method are regarded to be suitable respectively for both two- and three-dimensional numerical simulations of problems involving supported construction process in geotechnical engineering. As an engineering example，the cavern group of the underground powerhouse of Guandi Hydropower Station on the Yalong River in Southwest China is analyzed. The two-dimensional FLAC analysis is performed firstly for the optimization of location and spacing schemes of the three main chambers，i.e. the generator chamber，the main transformer chamber and the tail water surge chamber，considering their parallel arrangement and the modeling efficiency and computing cost. Then，the entirely-supported construction process of the cavern group of the underground powerhouse under the determined optimal layout scheme is simulated in three dimensions with FLAC3D. The distributions of displacement，stress and plastic deformation in the rock masses surrounding the caverns and the loads carried by the supporting structures are obtained. It is proven by the results that the numerical simulations of the layout and construction process of underground powerhouse with explicit finite difference method using respectively FLAC2D and FLAC3D match those of the practical case. The results from nonlinear stress analyses can be used to guide the design of excavations and rock supporting mechanisms.
