煤岩张剪裂隙震源机制及应力反演方法

Tensile–Shear Microcrack Source Mechanism and Stress Inversion Methods of Coal–Rock

  • 摘要: 精准监测与定量反演煤岩裂隙形态及应力场分布特征,是揭示冲击地压演化过程及致灾机理的科学基础,更是解决深地工程动力灾变演化问题的重要手段。以位移不连续理论为基础建立不同破裂类型的裂隙震源模型,通过修正Bott假设,提出适用于张剪裂隙类型的应力反演模型,并融合格里菲斯与摩尔−库仑准则构建复合破裂判据,实现真实裂隙面的有效识别,并以震源机制参数及应力场参数的最优适配为目标,进一步提出裂隙震源与应力联合迭代反演方法,并开展了实验室尺度的煤岩破坏监测反演的实践应用。结果表明:偏移角α可有效区分张拉、剪切及压缩等破坏类型,提出基于张剪复合失效准则的裂隙面与应力迭代求解方法,有效选取真实裂隙面提高应力反演精度,建立裂隙震源与应力的联合交替迭代模型,可有效减少理论滑移方向与真实滑移方向的偏差。在煤岩三点弯曲试验过程中,偏移角α主要处于0°~20°,表明破裂微裂纹主要为张剪复合类型,利用应力反演模型求得最大主应力σ1为拉应力,中间主应力σ2和最小主应力σ3为压应力,应力形状比平均值为0.87,表明σ1占主导作用,σ2σ3几乎相等,符合三点弯曲试样的受力状态,应力分布影响了试样裂纹运动方向主要为沿X轴方向的张拉分离,并促进了裂纹取向为沿Y轴方向的发育扩展。另外,应力旋转作用导致裂纹面取向在Y轴方向的分量被减小,裂纹运动方向与X轴方向的夹角增大,而这一改变随着应力旋转角度的增大得到加强。利用裂隙震源与应力联合迭代反演方法对应力反演过程进行优化,理论滑移方向与真实滑移方向之间的平均滑移偏差角依次降低了33.91%、79.86%和94.12%。将提出的张剪震源应力反演方法与VAVRYČUK方法进行对比,应力的形状比噪声误差率最大降低了6.49%,三向应力反演精度平均提升了15%~40%,研究成果可为煤岩体动力灾变演化研究提供一种科学方法,为深地工程冲击地压孕育机制解析与灾害预警提供新的理论支撑。

     

    Abstract: Precise monitoring and quantitative inversion of coal–rock fracture geometries and stress‐field distributions are regarded as fundamental scientific prerequisites for elucidating the evolution of rockburst processes and associated failure mechanisms, and are considered an essential approach for resolving dynamic disaster evolution in deep engineering. Microcrack source models corresponding to different fracture types are established on the basis of the displacement discontinuity theory. By modifying the Bott assumption, a stress inversion model applicable to tensile–shear fractures is proposed, and a composite failure criterion is constructed through the integration of the Griffith and Mohr–Coulomb criteria, enabling effective identification of true fracture planes. With the optimal compatibility between source‐mechanism parameters and stress‐field parameters taken as the target, a joint iterative inversion method of microcrack sources and stress fields is further developed, followed by laboratory‐scale monitoring and inversion experiments on coal–rock failure. The results indicate that the offset angle α effectively discriminates tensile, shear, and compressive fracture types. The iterative solution method for fracture planes and stress based on the tensile–shear composite failure criterion enables robust selection of true fracture planes and improves stress inversion accuracy. Establishment of a joint alternating inversion model of microcrack sources and stress effectively reduces the deviation between theoretical and actual slip directions. During three‐point bending tests on coal–rock specimens, α predominantly ranges between 0° and 20°, indicating that microcracks mainly exhibit tensile–shear composite characteristics. The stress inversion model yields a maximum principal stress σ1 in tension, whereas σ2 and σ3 are compressive. The average stress shape ratio reaches 0.87, demonstrating the dominance of σ1 and the near equivalence of σ2 and σ3, consistent with the loading state of three‐point bending specimens. The stress distribution governs crack motion predominantly as tensile separation along the X-axis and promotes crack development preferentially oriented along the Y-axis. Moreover, stress rotation reduces the Y-axis component of fracture‐plane orientation, increases the angle between crack motion and the X-axis, and this alteration intensifies with increasing rotation angle. Optimization of the stress inversion process using the joint inversion method progressively lowers the mean slip deviation angle between theoretical and actual slip directions by 33.91%, 79.86%, and 94.12%, respectively. Compared with the VAVRYČUK method, the proposed tensile–shear source stress inversion method achieves up to a 6.49% reduction in the noise error rate of the stress shape ratio, while improving the average accuracy of three‐directional stress inversion by approximately 15%–40%. These findings provide a rigorous methodological framework for investigating the dynamic failure evolution of coal–rock masses and offer new theoretical support for deciphering the incubation mechanisms of rockburst hazards and advancing disaster early-warning strategies in deep engineering.

     

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