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<p>To investigate the impact of tendon bond length on the bolt support system, this study examines the mechanical properties of rock bolt systems with varying bond lengths under axial load using a distributed optical fiber strain monitoring system, acoustic emission monitoring system, and pull-out tests system of rock bolts. The analysis focuses on the influence of bond length on the bearing capacity and failure modes of the rock bolt system. It has been found that: (1) The epoxy grout exhibits “scaly” crack zones at the boundary between its tensile and compressive strain regions. Interestingly, the spacing of these “scaly” cracks aligns with the thread spacing of the rock bolt, indicating that stress concentration at the rock bolt’s threads causes the cracks in the grout. (2) Under axial loading, the grout–rock interface first debonds near the beginning of the bonded section, reducing the effective bond length. This leads to increased shear stress at the grout–rock interface. When the shear stress exceeds the bond strength, further debonding occurs, and the debonded region propagates toward the bottom of the anchor segment as axial stress increases, ultimately resulting in complete failure of the rock bolt system. (3) When the bond length is short, the primary failure mode of the rock bolt system is debonding failure at the bond length involving both tendon–grout and grout–rock interfaces. Conversely, when the bond length is sufficient, the primary failure mode is tensile failure of the bolt within the free section. Therefore, damage to the rock bolt system tends to initiate at the interface with the weaker bond of the tendon–grout and grout–rock interfaces, illustrating a “short-plate effect.”</p>

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Quantitative Assessment of Rock Bolt Bond Length on Load-Bearing Capacity and Failure Mechanisms

  • 期刊论文

  • 发表日期：

    2025年9月26日

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  • Chuanming Li,
  • Jiankui Bai,
  • Ruimin Feng,
  • Jucai Chang,
  • Wenbao Shi,
  • Xiang Gao,
  • Kun Wang,
  • Zhengrong Zhang,
  • Bochao Nie,
  • Chuan Li,
  • Jianguo Cao,
  • Qinghua Han

摘要

To investigate the impact of tendon bond length on the bolt support system, this study examines the mechanical properties of rock bolt systems with varying bond lengths under axial load using a distributed optical fiber strain monitoring system, acoustic emission monitoring system, and pull-out tests system of rock bolts. The analysis focuses on the influence of bond length on the bearing capacity and failure modes of the rock bolt system. It has been found that: (1) The epoxy grout exhibits “scaly” crack zones at the boundary between its tensile and compressive strain regions. Interestingly, the spacing of these “scaly” cracks aligns with the thread spacing of the rock bolt, indicating that stress concentration at the rock bolt’s threads causes the cracks in the grout. (2) Under axial loading, the grout–rock interface first debonds near the beginning of the bonded section, reducing the effective bond length. This leads to increased shear stress at the grout–rock interface. When the shear stress exceeds the bond strength, further debonding occurs, and the debonded region propagates toward the bottom of the anchor segment as axial stress increases, ultimately resulting in complete failure of the rock bolt system. (3) When the bond length is short, the primary failure mode of the rock bolt system is debonding failure at the bond length involving both tendon–grout and grout–rock interfaces. Conversely, when the bond length is sufficient, the primary failure mode is tensile failure of the bolt within the free section. Therefore, damage to the rock bolt system tends to initiate at the interface with the weaker bond of the tendon–grout and grout–rock interfaces, illustrating a “short-plate effect.”