Yudong Li, Min Xia, Jiayuan Fan, Qi Huang, Wenhui Zeng, Rongquan Fan

Base friction model test investigation of deformation modes of gently dipped layered surrounding rock

Santrauka This study investigates the deformation and failure mechanisms of gently layered surrounding rock during underground excavation in a hydropower station in Shaanxi Province, China, through base friction physical simulation tests. Results indicate rock mass instability is governed by weak discontinuities (layer planes, joints, and faults). Four failure modes emerge: (1) tensile crack collapse at the tunnel arch induced by stress concentration, (2) shear slip at the sidewalls and shoulders due to exceeding shear strength, (3) bulging deformation of thin-layered rock under compressive stress, and (4) slight uplift at the invert of the main powerhouse due to upward pressure. The physical simulation tests replicate the deformation and failure evolution of the surrounding rock mass during excavation. Initially, the process is characterized by tunnel arch spall and slight slip, progressing to rock mass collapse due to structural plane coalescence. The study reveals the complex mechanical behaviour of failure in gently layered surrounding rock. The tunnel arch exhibits a “tension crack collapse – shear slip – bedding” failure mode, while the sidewall is primarily influenced by shear slip. Findings confirm discontinuities’ control on the stability of layered surrounding rock, offering guidance for deformation support and long-term maintenance. These results provide significant theoretical and practical implications for engineering applications.

Doi https://doi.org/10.5200/baltica.2026.1.2

Raktažodžiai tunnel; gently-inclined layered rock mass; physical simulation; failure mechanisms

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