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<p>This study investigates the rockburst failure mechanism of circular caverns subjected to unilateral unloading through a combination of true-triaxial laboratory tests and discrete element numerical simulations (PFC). Granite specimens containing prefabricated circular holes were tested under four representative stress conditions. The results indicate that sidewall failure initiates when the maximum far-field principal stress reaches approximately 0.166–0.235<i>σ</i><sub><i>c</i></sub>. Unilateral unloading significantly weakens the surrounding rock, leading to a strength degradation exceeding 44.9%, with increasing axial stress proves more effective in mitigating damage than reducing lateral stress. Rockburst occurs predominantly on the sidewall opposite the unloading surface, forming a characteristic unilateral V-shaped notch. Numerical simulations reveal that strong force chains initially collapse on the sidewall adjacent to the unloading surface, then progressively migrate toward the opposite side, eventually triggering macroscopic spalling, with over 80% of failures tension-dominated. Unilateral unloading causes more sudden rockbursts than triaxial loading, typically forming a shallow V-shaped notch. These findings provide valuable guidance for predicting and controlling rockburst risks in sequentially excavated underground caverns.</p>

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Rockburst failure mechanism of deep circular caverns induced by unilateral unloading

  • 期刊论文

  • 发表日期：

    2026年6月25日

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  • Zhaoxi Yan,
  • Xiang Li,
  • Kewei Liu,
  • Jiacai Yang,
  • Longfeng Chen,
  • Peiyu Wang

摘要

This study investigates the rockburst failure mechanism of circular caverns subjected to unilateral unloading through a combination of true-triaxial laboratory tests and discrete element numerical simulations (PFC). Granite specimens containing prefabricated circular holes were tested under four representative stress conditions. The results indicate that sidewall failure initiates when the maximum far-field principal stress reaches approximately 0.166–0.235σc. Unilateral unloading significantly weakens the surrounding rock, leading to a strength degradation exceeding 44.9%, with increasing axial stress proves more effective in mitigating damage than reducing lateral stress. Rockburst occurs predominantly on the sidewall opposite the unloading surface, forming a characteristic unilateral V-shaped notch. Numerical simulations reveal that strong force chains initially collapse on the sidewall adjacent to the unloading surface, then progressively migrate toward the opposite side, eventually triggering macroscopic spalling, with over 80% of failures tension-dominated. Unilateral unloading causes more sudden rockbursts than triaxial loading, typically forming a shallow V-shaped notch. These findings provide valuable guidance for predicting and controlling rockburst risks in sequentially excavated underground caverns.