Abstract: The construction of underground powerhouses for hydropower stations has always been a focal point and challenge in design and construction due to their large scale, high side walls, extensive spans, and complex geological conditions. This study relies on the Shuangjiangkou hydropower station, known for having the highest geostress globally, to investigate the engineering issues related to hard rock deformation and failure under extremely high stress, along with stability control methods. The research is divided into two main aspects: Firstly, we estimate and adjust the in-situ stress field of underground caverns in deep-cut valley areas using limited geostress test data and the brittle failure phenomena observed in the pilot tunnels. Secondly, we examine the typical failure phenomena of underground caverns under extremely high stress, including global issues from high-stress failure and block instability due to localized rock veins cutting, along with corresponding failure mechanisms and control measures. The findings offer valuable case studies and references for constructing large underground caverns in high-stress hard rock environments.

Key words: large underground caverns, high stress, failure phenomena, rock vein, stability control