Study on the stability assessment of surrounding rock under combined support conditions for a cavern group spanning a large-scale fault zone

Abstract The stability of underground cavern groups spanning complex fault zones is a critical challenge in deep underground engineering construction. This study establishes a comprehensive numerical model of the caverns using FLAC3D to evaluate the stability of the surrounding rock of a hydropower station cavern group spanning a large-scale fault zone under combined support conditions, focusing on stress and plastic zone analyses. The results indicate that, under the combined support scheme, the tensile and compressive stresses of the shotcrete remain within the allowable limits specified by relevant standards; the area of the plastic zone in the surrounding rock is significantly reduced and does not interconnect. These findings theoretically validate the rationality of the combined support scheme. This study provides essential design and construction references for underground cavern group projects in complex fault zones, offering significant practical implications for ensuring the safe construction of deep underground engineering projects.