Analysis of underground cavern surrounding rock stability and anchoring effects under high stress using an optimized DDA-RF method

This study focuses on the stability of surrounding rock (SR) in underground cavities of China’s western high-stress regions, using the tailwater pressure–regulating chamber of a hydropower station on the lower Jinsha River as the case. Models with and without bolts are established for excavation simulation. Based on the key assumptions of linear elastic rock blocks, fully bonded bolt–rock interface, and instantaneous excavation unloading, results show that SR failure follows a vault → walls → floor sequence consistent with excavation order. Bolts significantly enhance stability: They reduce fractured zone depth (defined as the maximum distance from excavation boundary to continuous fractured network) by 33.33% in the vault and right wall (from 6 to 4 m) and 25% in the left wall (from 8 to 6 m). For displacement (measured as absolute movement of key monitoring points relative to initial state), bolts achieve an 86.96% reduction in vault settlement (from 93.64 to 12.21 mm) and 71.38% reduction in right wall convergence (from 21.63 to 6.19 mm). However, the F1 structural plane limits bolt effectiveness on the left wall and floor, where fractured zone depth remains unchanged at 2 m. This study provides scientific support for support design in high-stress underground projects.

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