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<p>Tensile–shear coupling failure of bolts under deep and complex environmental conditions is a primary cause of surrounding rock instability in coal mine roadways. To analyze failure mechanisms and improve support durability, this study developed a tensile–shear testing apparatus to simulate underground conditions. By integrating mechanical testing, micro-/mesoscale characterization, and numerical simulation, bolt load-bearing behavior and failure mechanisms were systematically investigated under varying conditions. The results indicate that installation angle and shear gap exert a pronounced influence on bolt performance, whereas pretension torque and axial force show limited effects. Accordingly, a 15° installation angle in roadway shoulder zones is recommended, together with reinforcement of the support system to alleviate shear stress concentration in the bolt body. Comparative analysis demonstrated the superior durability of fine-threaded bolts under complex loading. Consequently, a novel fine-threaded bolt was developed to mitigate surface stress concentration. Under combined loading, this optimized bolt reduced the plastic zone area by 23.35% and eliminated high-stress regions exceeding 800&#xa0;MPa, substantially lowering failure risk and supporting safe deep roadway operations.</p>

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Failure Mechanism and Control Strategies of Tensile–Shear Coupling in Bolts Under Complex Conditions

  • 期刊论文

  • 发表日期：

    2026年4月6日

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  • Zhe He,
  • Nong Zhang,
  • Zhengzheng Xie,
  • Peng Wang,
  • Zhe Xiang,
  • Zhiwen Chen,
  • Wei Li,
  • Asaad Algarni

摘要

Tensile–shear coupling failure of bolts under deep and complex environmental conditions is a primary cause of surrounding rock instability in coal mine roadways. To analyze failure mechanisms and improve support durability, this study developed a tensile–shear testing apparatus to simulate underground conditions. By integrating mechanical testing, micro-/mesoscale characterization, and numerical simulation, bolt load-bearing behavior and failure mechanisms were systematically investigated under varying conditions. The results indicate that installation angle and shear gap exert a pronounced influence on bolt performance, whereas pretension torque and axial force show limited effects. Accordingly, a 15° installation angle in roadway shoulder zones is recommended, together with reinforcement of the support system to alleviate shear stress concentration in the bolt body. Comparative analysis demonstrated the superior durability of fine-threaded bolts under complex loading. Consequently, a novel fine-threaded bolt was developed to mitigate surface stress concentration. Under combined loading, this optimized bolt reduced the plastic zone area by 23.35% and eliminated high-stress regions exceeding 800 MPa, substantially lowering failure risk and supporting safe deep roadway operations.