Study on Dynamic Stability of Large-Scale Underground Cavern Group during Construction Period of Hydropower Station

Abstract

Taking excavation and supporting of surge tank large-scale underground cavern group of Nuozhadu hydropower station as example, the stability of surrounding rock is analyzed systematically, and the best lining scheme is obtained. Through primary supporting calculation, the displacement and the small main stress increases continuously with excavation of cavern; the rock-point safety factor of decreases continuously with excavation of cavern; the displacement, the small main stress and the rock-point safety factor soon changed when the surrounding rock unloaded suddenly, therefore, the surrounding rock must be supported timely. After excavation, the maximum total displacement is 10.57mm, the maximum tensile stress is far less than the tensile strength of surrounding rock, and the minimum safety factor of key point does not satisfy the requirement of standard; the surrounding rock surface will be broken but not large-area damage basis of excavation. The key point’s safety factor changes and the safety factor satisfies the standard requirement only when the elevation of the second lining larger than this key point. According to lining scheme comparison, the scheme that concrete of surge tank pouring to elevation 625.5m is the most economic and reasonable lining scheme for this engineering.