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<p>The phenomenon of rock-bursts, which are exacerbated by elevated surrounding rock stress and intricate lithological conditions, becomes more prevalent in deep mining operations, thereby posing significant risks to safety in production. To investigate the failure mechanisms of surrounding rocks at depth, particularly in relation to lithological effects and lateral constraints, a series of true triaxial tests incorporating acoustic emission (AE) techniques were conducted. These tests aimed to analyze the mechanical behavior of coal-rock combinations under varying lithological conditions and orientations of maximum principal stress, while also examining the damage mechanisms and AE precursor characteristics associated with these combinations. The findings reveal that during triaxial compression testing, the ultimate strength of coal-rock combinations diminishes by 1.2% to 15.5% when the direction of the maximum principal stress shifts from the <i>Z</i>-axis to the <i>Y</i>-axis. Conversely, the strength of intact coal/rock increases by 13.7%–51.6%. coal-rock combinations dominated by shear failure, whose proportion is 5.6%–11.2% higher than that in intact coal/rock specimens, whereas intact samples exhibit tension–shear coupled failure. The spatial extent of shear cracks expands with increasing lateral stress difference: when the difference rises from 5 to 15&#xa0;MPa, the range widens by 6.8%–12.5%. Reorienting the maximum principal stress to the Y-axis raises the incidence of shear cracks near the σ₂ direction by 9.5%–18.6%. Acoustic-emission evolution shows that a larger strength contrast within the assembly (coarse sandstone–coal) shortens the stable AE phase by 32.2% and increases event frequency by 16.7%, whereas high-strength intact rocks (siltstone) prolong the stable phase by 27.3%. When lateral stress surpasses 15&#xa0;MPa, there is a notable reduction in the initiation and damage evolution of cracks in coal and rock, attributed to the influence of lateral stress, while the impact of maximum principal stress becomes significantly more pronounced.</p>

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Failure Mechanism of Deep Surrounding Rock Influenced by Effects of Lithology and Lateral Constraint Under True Triaxial Stress

  • 期刊论文

  • 发表日期：

    2025年8月21日

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  • Hongyue Ren,
  • Wei Zhang,
  • Weiyao Guo,
  • Baoliang Zhang

摘要

The phenomenon of rock-bursts, which are exacerbated by elevated surrounding rock stress and intricate lithological conditions, becomes more prevalent in deep mining operations, thereby posing significant risks to safety in production. To investigate the failure mechanisms of surrounding rocks at depth, particularly in relation to lithological effects and lateral constraints, a series of true triaxial tests incorporating acoustic emission (AE) techniques were conducted. These tests aimed to analyze the mechanical behavior of coal-rock combinations under varying lithological conditions and orientations of maximum principal stress, while also examining the damage mechanisms and AE precursor characteristics associated with these combinations. The findings reveal that during triaxial compression testing, the ultimate strength of coal-rock combinations diminishes by 1.2% to 15.5% when the direction of the maximum principal stress shifts from the Z-axis to the Y-axis. Conversely, the strength of intact coal/rock increases by 13.7%–51.6%. coal-rock combinations dominated by shear failure, whose proportion is 5.6%–11.2% higher than that in intact coal/rock specimens, whereas intact samples exhibit tension–shear coupled failure. The spatial extent of shear cracks expands with increasing lateral stress difference: when the difference rises from 5 to 15 MPa, the range widens by 6.8%–12.5%. Reorienting the maximum principal stress to the Y-axis raises the incidence of shear cracks near the σ₂ direction by 9.5%–18.6%. Acoustic-emission evolution shows that a larger strength contrast within the assembly (coarse sandstone–coal) shortens the stable AE phase by 32.2% and increases event frequency by 16.7%, whereas high-strength intact rocks (siltstone) prolong the stable phase by 27.3%. When lateral stress surpasses 15 MPa, there is a notable reduction in the initiation and damage evolution of cracks in coal and rock, attributed to the influence of lateral stress, while the impact of maximum principal stress becomes significantly more pronounced.