不同载荷作用下含瓦斯煤岩组合体能量演化行为及渐进损伤特性
Energy evolution and progressive damage characteristics of gas-bearing coal-rock combination under different loads
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摘要: 研究常规三轴载荷和分级循环载荷作用下含瓦斯煤岩组合体能量演化特征及渐进损伤行为, 对深部煤岩瓦斯复合动力灾害的防控具有重要意义。采用实验室试验、理论分析等研究方法, 开展了不同围压和应力载荷的声发射−渗流−损伤三轴同步试验, 分析了受载含瓦斯煤岩组合体的力学响应特征、渐进损伤行为及能量演化规律, 结合宏−细观破坏特征, 揭示了围压及应力载荷对含瓦斯煤岩组合体失效行为的影响机制。研究结果表明: ①组合体试样的峰值强度、弹性模量、残余强度均随围压增加线性增大, 在围压相同时, 分级循环载荷下的弹性模量比常规三轴载荷低0.13~1.76 GPa, 峰值强度比常规三轴载荷低8.91%~20.81%; ②围压升高显著抑制裂隙发育, 但分级循环载荷的起裂应力比和损伤应力比更低, 试样更易在低应力下产生裂纹; ③试样声发射信号随渐进损伤特征应力呈阶段性变化特征, 峰值声发射计数随围压的提高而增大。围压的增加会限制试样内部裂纹的扩展和贯通, 分级循环载荷下, 声发射计数的Kaiser效应区延长, Felicity效应区缩短; ④分级循环载荷的总能量、弹性能和耗散能均高于常规三轴载荷, 较大应力幅值区间内能量耗散更显著, 试样破坏面的SEM细观结构更加复杂和粗糙, 裂纹和孔隙特征更加明显, 分形维数值比常规三轴载荷大0.057~0.280; ⑤高围压产生的损伤作用大于压缩限制作用, 加剧了煤岩组合体的界面破坏效应, 破坏模式以剪切破坏为主。研究结果为深部煤层开采过程中高应力、高瓦斯压力区的煤岩瓦斯复合动力灾害防控提供理论依据。Abstract: It is of significant importance to investigate the energy evolution characteristics and progressive damage behavior of gas-bearing coal-rock combinations under both conventional and graded cyclic loading conditions for the prevention and control of deep coal-rock-gas composite dynamic disasters. By laboratory testing and theoretical analysis, a series of coupled acoustic emission (AE)-seepage-damage triaxial tests were conducted under various confining pressures and stress paths. The mechanical response, progressive damage behavior, and energy evolution patterns of loaded gas-bearing coal-rock combinations were systematically analyzed. By combining macro-meso failure characteristics, the influence mechanisms of confining pressure and stress loading on the failure behavior of gas-bearing coal-rock combinations were revealed. The results show that the peak strength, elastic modulus and residual strength of the composite specimens increase linearly with confining pressure. Under the same confining pressure, the elastic modulus under graded cyclic loading is lower by 0.13−1.76 GPa, and the peak strength is lower by 8.91%−20.81% than those under the conventional triaxial loading. Increasing confining pressure significantly suppresses crack development, while graded cyclic loading exhibits the lower crack initiation stress and damage stress ratios, making specimens more prone to cracking at lower stress levels. Acoustic emission (AE) signals exhibit stage-wise variations corresponding to characteristic stresses during progressive damage. Peak acoustic emission counts increase with higher confining pressure. Elevated confining pressure restricts internal crack propagation and coalescence. Under graded cyclic loading, the Kaiser effect zone of acoustic emission counts extends, while the Felicity effect zone shortens. The total energy, elastic energy and dissipated energy under graded cyclic loading are all higher than those under conventional triaxial loading. Energy dissipation is more pronounced in intervals with the larger stress amplitudes. SEM observations reveal more complex and rougher failure surfaces under graded cyclic loading, with more evident cracks and pores, and fractal dimension values larger by 0.057−0.280 than that under conventional triaxial loading. High confining pressure induces greater damage effects than compressive restrictions, exacerbating interfacial failure in coal-rock combinations, with shear failure being the dominant failure mode. These findings provide a theoretical basis for preventing and controlling coal and gas composite dynamic disasters in high-stress and high-gas-pressure zones in deep coal mining.
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