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<p>The mechanism of shear failure of rock bridges, which are the core load-bearing parts of nonpersistent joints in natural rock masses, under confining pressures is crucial for the stability of deep engineering projects. In this study, the mechanical responses and fracture characteristics of granite samples with different rock bridge lengths were investigated using triaxial shear testing systems via the short core compression (SCC) method. The results demonstrate that the confining pressure significantly enhances the shear strength of rock bridges by strengthening normal constraints; the confining pressure also suppresses lateral expansion and promotes shear-dominated failure. Under low confining pressures (≤ 10 MPa), the rock bridge length regulates modes of failure: short bridges exhibit homogeneous shear failure due to stress concentration, whereas long bridges develop multistage microcracks under tensile–shear coupling, resulting in a higher roughness. Experiments reveal that high confining pressures (&gt; 10 MPa) induce smoother shear surfaces with a more uniform height distribution of asperities. Finite element analysis reveals that confining pressure regulates crack propagation paths by modifying stress intensity factors, with more pronounced stress concentrations in short bridge samples, for which a new pressure-dependent correction model was proposed. The SCC-derived shear strength parameters were validated against direct shear and triaxial compression tests. Numerical simulations of tunnel excavation further confirmed the applicability of the SCC-derived parameters. The findings provide theoretical and experimental foundations for the assessment of stability and hazard prevention in deep rock engineering projects while offering novel insights for optimizing high-confining-pressure shear testing methodologies.</p>

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Experimental Study on Shear Failure Mechanism of Granite with Different Length of Rock Bridge Under Confining Pressure

  • 期刊论文

  • 发表日期：

    2025年11月20日

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  • Dekang Sun,
  • Hanpeng Wang,
  • Yuguo Zhou,
  • Bing Zhang,
  • Fubin Hou,
  • Jinhou Zhang,
  • Yunhao Wu

摘要

The mechanism of shear failure of rock bridges, which are the core load-bearing parts of nonpersistent joints in natural rock masses, under confining pressures is crucial for the stability of deep engineering projects. In this study, the mechanical responses and fracture characteristics of granite samples with different rock bridge lengths were investigated using triaxial shear testing systems via the short core compression (SCC) method. The results demonstrate that the confining pressure significantly enhances the shear strength of rock bridges by strengthening normal constraints; the confining pressure also suppresses lateral expansion and promotes shear-dominated failure. Under low confining pressures (≤ 10 MPa), the rock bridge length regulates modes of failure: short bridges exhibit homogeneous shear failure due to stress concentration, whereas long bridges develop multistage microcracks under tensile–shear coupling, resulting in a higher roughness. Experiments reveal that high confining pressures (> 10 MPa) induce smoother shear surfaces with a more uniform height distribution of asperities. Finite element analysis reveals that confining pressure regulates crack propagation paths by modifying stress intensity factors, with more pronounced stress concentrations in short bridge samples, for which a new pressure-dependent correction model was proposed. The SCC-derived shear strength parameters were validated against direct shear and triaxial compression tests. Numerical simulations of tunnel excavation further confirmed the applicability of the SCC-derived parameters. The findings provide theoretical and experimental foundations for the assessment of stability and hazard prevention in deep rock engineering projects while offering novel insights for optimizing high-confining-pressure shear testing methodologies.