Abstract: Dagangshan hydroelectric power station is a large scale hydropower project developed recently on the Dadu River. In order to analyze the stability of surrounding rock of underground powerhouse caverns during construction excavation, the multiple regression analysis method is employed to inverse the initial geostress field of plant zone, and the functions of initial stress distribution are proposed. The variation regularities of displacement field, stress field and plastic zone of underground powerhouse caverns after excavation are obtained according to the established 3-D numerical computational model. Computing results show that the surrounding rock of Dagangshan underground caverns is stable as a whole after excavation. The weak rock veins are key factors influencing the stability of surrounding rock of underground powerhouse. The soft rock veins and fracture zone must be pre-grouted and reinforced during construction. These computation conclusions have guided the design and construction of the project effectively.

Key words: Dagangshan hydropower station, underground powerhouse stability of surrounding rock, multiple regression analysis, 3-D numerical computational model