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<p>The rock discontinuities of rock masses significantly affect the safety and stability of deep mining, traffic tunnels, and large underground caverns. In deep underground engineering, the surrounding rock mass is subjected to three-dimensional (3D) high-stress conditions while simultaneously experiencing dynamic disturbances from multiple directions owing to blasting and mechanical excavation. However, the shear mechanical behavior and fracture mechanisms of rock mass rock discontinuities under the combined effects of 3D stress and dynamic disturbances remain unclear. This study employed a newly developed shear testing system to propose a true triaxial disturbance shear testing method for investigating the fracture behavior in rock mass rock discontinuities under 3D disturbances. Through true triaxial shear tests on limestone rock discontinuities with varying disturbance amplitudes and frequencies, this study analyzed their effects on the mechanical behavior and fracture evolution, including the disturbance shear strength, deformation characteristics, fracture surface morphology, and energy evolution patterns. The results indicated that as the disturbance amplitude and frequency increased, the disturbance critical strength decreased, whereas the fracture surface anisotropy, deformation ductility, and rock mass energy accumulation (total strain energy, elastic strain energy, and disturbance dissipation energy) exhibited an increasing trend. Higher disturbance amplitudes produced smoother fracture surfaces with a near-linear decrease in roughness, whereas higher disturbance frequencies generated rougher fracture surfaces with increasing roughness at an accelerating rate. A higher disturbance amplitude (or lower frequency) led to earlier crack initiation within the rock mass rock discontinuities and more localized acoustic emission (AE) events near the planes. During disturbance shear fracturing, the microtensile cracks consistently dominated, while the micro-shear cracks gradually increased as the disturbance amplitude and frequency increased. As the 3D-disturbance shear failure approached, notable AE precursors emerged, including a rapid decrease in the <i>b</i> value, sudden increase in the fractal dimension, and significant rise in high-amplitude AE events.</p>

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Shear Failure Mechanism and Precursors of Rock Discontinuities Triggered by 3D-Disturbance During Tunnel Excavation

  • 期刊论文

  • 发表日期：

    2025年10月6日

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  • Zhi Zheng,
  • Feng Yu,
  • Shaojun Li,
  • Wuqiang Cai,
  • Shili Qiu,
  • Wei Wang

摘要

The rock discontinuities of rock masses significantly affect the safety and stability of deep mining, traffic tunnels, and large underground caverns. In deep underground engineering, the surrounding rock mass is subjected to three-dimensional (3D) high-stress conditions while simultaneously experiencing dynamic disturbances from multiple directions owing to blasting and mechanical excavation. However, the shear mechanical behavior and fracture mechanisms of rock mass rock discontinuities under the combined effects of 3D stress and dynamic disturbances remain unclear. This study employed a newly developed shear testing system to propose a true triaxial disturbance shear testing method for investigating the fracture behavior in rock mass rock discontinuities under 3D disturbances. Through true triaxial shear tests on limestone rock discontinuities with varying disturbance amplitudes and frequencies, this study analyzed their effects on the mechanical behavior and fracture evolution, including the disturbance shear strength, deformation characteristics, fracture surface morphology, and energy evolution patterns. The results indicated that as the disturbance amplitude and frequency increased, the disturbance critical strength decreased, whereas the fracture surface anisotropy, deformation ductility, and rock mass energy accumulation (total strain energy, elastic strain energy, and disturbance dissipation energy) exhibited an increasing trend. Higher disturbance amplitudes produced smoother fracture surfaces with a near-linear decrease in roughness, whereas higher disturbance frequencies generated rougher fracture surfaces with increasing roughness at an accelerating rate. A higher disturbance amplitude (or lower frequency) led to earlier crack initiation within the rock mass rock discontinuities and more localized acoustic emission (AE) events near the planes. During disturbance shear fracturing, the microtensile cracks consistently dominated, while the micro-shear cracks gradually increased as the disturbance amplitude and frequency increased. As the 3D-disturbance shear failure approached, notable AE precursors emerged, including a rapid decrease in the b value, sudden increase in the fractal dimension, and significant rise in high-amplitude AE events.