Numerical Simulation of Stability for Underground Powerhouse Cavern Group of Jinping Hydropower Station

A brief introduction is given to the great challenge during construction of Jinping hydropower station for four tunnels with small space, which is a key cascade underground hydropower project, located in the Southwest China, at the Yalong River. The vertical geo-stress (63MPa) is highest in similar engineering in China. Through numerical simulation, comparison with displacements, energy density and plastic zone of surrounding rock, a detailed description is carried out to calculate and analyze for different spaces between adjacent tunnel´s centers. Horizontal displacements of two lateral walls are unsymmetrical extremely. But it is symmetric fundamentally for walls of medial tunnels. Consequently, more attention should be paid to outboard tunnels displacement during construction of cavern group. There is increasing zone of energy occurrence at surrounding rock upper the vault (2m~3m), which plays an important role in integral stability of cavern group and needs to be strengthened for design. The minimum safety space between adjacent tunnel is 40~45m. The actual space of Jinping hydropower cavern group is 60m, so it is safe. Not only is the analysis method fit for Jinping hydropower station, but it can be as reference for similar cavern group engineering.