A comprehensive analysis of crack initiation and propagation in coal is critical for understanding its mechanical behavior and its impact on permeability. The finite element-based digital volume correlation (DVC) of time-resolved X-ray tomography images under cleat-parallel uniaxial compression provides 3D incremental strain fields to understand the evolution and propagation of cracks. In this study, DVC coupled with quantitative image analysis was used to understand the role of cleats in guiding and initiating cracks in coal. Simulation of fluid flow through coal at different loading segments provides dynamic quantification of evolution in permeability. After each loading stage, quantification of strain eigen vectors and image analysis indicates appearance, coexistence, and coalescence of tensile and shear cracks guided by the organic matter in coal. We established that constructive interference between tensile and shear crack systems enhances permeability and decreases tortuosity by almost 3x and 7x respectively in coal by widening crack aperture, however, destructive interference is likely to lead to matrix pulverization and clogging of larger crack apertures. During compression, while one part of the coal matrix shows extension perpendicular to the loading direction, another part shows slippage parallel to the loading direction. Based on the variation in crack propagation behavior, four distinct crack morphology zones were identified and discussed. We found that the tortuosity of the cracks decreases exponentially, while permeability and crack volume fraction increase exponentially up to 2.8 μm² and 28.6% respectively with increasing load. The box-counting-based fractal dimension for the cracks shows a steady increase from 1.58 to 1.78 with loading due to the evolution of existing cracks, and the formation of new cracks.

全面分析煤中的裂纹萌生和扩展对于了解其力学行为及其对渗透性的影响至关重要。夹板平行单轴压缩下时间分辨 X 射线断层扫描图像的基于有限元的数字体积相关性 (DVC) 提供了 3D 增量应变场，以了解裂纹的演变和扩展。在这项研究中，DVC 与定量图像分析相结合，用于了解夹板在引导和引发煤裂缝中的作用。在不同装载段模拟流体流过煤，提供了渗透率演变的动态量化。在每个加载阶段之后，应变特征向量的量化和图像分析表明外观、共存和合并煤中有机质引导的拉伸和剪切裂纹。我们确定，拉伸和剪切裂纹系统之间的相长干涉通过扩大裂缝孔径分别提高了煤的渗透性和弯曲度几乎 3 倍和 7 倍，但是，相消干涉可能导致基体粉碎和较大裂缝孔径的堵塞。在压缩过程中，煤基体的一部分显示出垂直于加载方向的延伸，另一部分显示出平行于加载方向的滑移。基于裂纹扩展行为，四个不同的裂纹形态区域被识别和讨论。我们发现裂纹的曲折度呈指数下降，而渗透率和裂纹体积分数随着载荷的增加分别呈指数增加至 2.8 μm ²和 28.6%。由于现有裂纹的演变和新裂纹的形成，裂纹的基于盒计数的分形维数随着载荷从 1.58 稳定增加到 1.78。