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<p>To examine the influence of non‑persistent fracture geometry on the anisotropic shear‑compression response of rock masses and the associated bolt reinforcement mechanisms, a series of rock‑like specimens was fabricated containing fractures with systematically varied persistence, aperture, offset distance, and dip angle. Direct shear tests were conducted under a constant normal stress of 5&#xa0;MPa, and the geometric attributes of the resultant fracture networks—including crack type, length, and orientation—were quantitatively characterized using ImageJ analysis software.The results demonstrate that, among the geometric parameters examined, fracture persistence engenders the most pronounced degradation in shear strength and should therefore be regarded as the primary controlling parameter in reinforcement design. Dip angle governs the evolution of failure mode: at low inclination angles (0–30°), failure is dominated by wing‑crack initiation and shear slip, whereas at higher angles (60–90°), the mechanism transitions to a combined mode involving wing cracking and triangular‑zone diffraction, with the 60° specimen exhibiting the highest crack density. Quantitative mapping of the fracture networks reveals that secondary shear cracks are predominantly localized within the 21–40&#xa0;mm length range and the 120–150° orientation interval. In contrast, wing cracks display the greatest propagation capacity, attaining average lengths of approximately 50&#xa0;mm. Bolt reinforcement substantially suppresses the development of secondary shear cracks through dowel action and modification of the local stress path, thereby promoting a transition from brittle to ductile behavior. Nevertheless, its restraining effect on wing‑crack propagation remains limited. Reinforcing efficiency attains a maximum at a dip angle of 15°, although under this condition the bolt is subjected to severe combined shear–tensile loading, rendering it particularly susceptible to necking‑induced plastic failure.This study furnishes a quantitative assessment of the coupling between geometric anisotropy of fractures and bolt reinforcement mechanisms, elucidating their synergistic interplay in dictating failure modes and crack propagation characteristics. The findings establish a rigorous theoretical foundation for the development of differentiated bolt‑support strategies in fractured rock masses.</p>

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Experimental Study on Shear Anisotropy and Anchoring Mechanism of Fractured Rock Masses

  • 期刊论文

  • 发表日期：

    2026年5月10日

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  • Shuguang Zhang,
  • Jiamian Lin,
  • Wenbo Liu,
  • Xiang Huang,
  • Dipeng Zhu,
  • Wenwu Ou,
  • Shutian Zhao,
  • Yipin Liu,
  • Yingbo Li

摘要

To examine the influence of non‑persistent fracture geometry on the anisotropic shear‑compression response of rock masses and the associated bolt reinforcement mechanisms, a series of rock‑like specimens was fabricated containing fractures with systematically varied persistence, aperture, offset distance, and dip angle. Direct shear tests were conducted under a constant normal stress of 5 MPa, and the geometric attributes of the resultant fracture networks—including crack type, length, and orientation—were quantitatively characterized using ImageJ analysis software.The results demonstrate that, among the geometric parameters examined, fracture persistence engenders the most pronounced degradation in shear strength and should therefore be regarded as the primary controlling parameter in reinforcement design. Dip angle governs the evolution of failure mode: at low inclination angles (0–30°), failure is dominated by wing‑crack initiation and shear slip, whereas at higher angles (60–90°), the mechanism transitions to a combined mode involving wing cracking and triangular‑zone diffraction, with the 60° specimen exhibiting the highest crack density. Quantitative mapping of the fracture networks reveals that secondary shear cracks are predominantly localized within the 21–40 mm length range and the 120–150° orientation interval. In contrast, wing cracks display the greatest propagation capacity, attaining average lengths of approximately 50 mm. Bolt reinforcement substantially suppresses the development of secondary shear cracks through dowel action and modification of the local stress path, thereby promoting a transition from brittle to ductile behavior. Nevertheless, its restraining effect on wing‑crack propagation remains limited. Reinforcing efficiency attains a maximum at a dip angle of 15°, although under this condition the bolt is subjected to severe combined shear–tensile loading, rendering it particularly susceptible to necking‑induced plastic failure.This study furnishes a quantitative assessment of the coupling between geometric anisotropy of fractures and bolt reinforcement mechanisms, elucidating their synergistic interplay in dictating failure modes and crack propagation characteristics. The findings establish a rigorous theoretical foundation for the development of differentiated bolt‑support strategies in fractured rock masses.