Ma Xingying, Gong Xuanping, Cheng Xiaoyu, Cheng Cheng, Yang Peng, Xiao Lu, Sun Yongxin, Sun Baoqiang
China Coal Energy Research Institute Co., Ltd., Xi'an 710054, China.
School of Emergency Management and Safety Engineering, China University of Mining & Technology (Beijing), Beijing 10083, China.
ACS Omega. 2025 Sep 13;10(37):42933-42946. doi: 10.1021/acsomega.5c05736. eCollection 2025 Sep 23.
To investigate the influence of the confining pressure and axial loading rate on the damage-permeability characteristics of gas-containing coal, a solid-gas coupling experimental platform for coal was utilized to conduct damage-permeability experiments under varying confining pressures and axial loading rates. The study aimed to explore the coupling mechanism between coal damage and permeability under different influencing factors, providing a theoretical basis for determining the optimal extraction window during coalbed gas extraction. The results indicate that higher loading rates lead to a slight increase in the peak axial stress of coal samples in the stress-strain curve, with the permeability peak point lagging behind the axial stress peak point. As the confining pressure increases, the compressive strength of coal gradually improves but the permeability continuously decreases. Under uniaxial compression, coal samples exhibit an X-shaped conjugate inclined shear or single inclined shear failure. Higher loading rates result in greater damage to the coal samples, more complex failure patterns, and larger crack lengths and apertures, whereas higher confining pressures inhibit the further development of failure patterns. Based on the fractal dimension of coal surface damage, the surface fractal dimension of coal decreases linearly with increasing confining pressure after loading, further confirming that higher confining pressure reduces the complexity of crack development in coal samples. Therefore, in engineering practice, selecting the optimal window for gas extraction requires comprehensive consideration of the effects of mining speed and confining pressure as well as rational allocation of extraction negative pressure in different zones, to achieve efficient coalbed gas extraction.
为研究围压和轴向加载速率对含瓦斯煤损伤-渗透特性的影响，利用煤的固气耦合实验平台，在不同围压和轴向加载速率下进行损伤-渗透实验。该研究旨在探究不同影响因素下煤损伤与渗透率之间的耦合机制，为确定煤层气开采过程中的最佳抽采窗口期提供理论依据。结果表明，较高加载速率会使煤样应力-应变曲线中的轴向应力峰值略有增加，渗透率峰值点滞后于轴向应力峰值点。随着围压增大，煤的抗压强度逐渐提高，但渗透率持续降低。在单轴压缩下，煤样呈现X形共轭斜剪或单斜剪破坏。较高加载速率会使煤样损伤更大、破坏模式更复杂、裂纹长度和开度更大，而较高围压会抑制破坏模式的进一步发展。基于煤表面损伤的分形维数，加载后煤的表面分形维数随围压增大呈线性减小，进一步证实较高围压降低了煤样裂纹发育的复杂程度。因此，在工程实践中，选择最佳瓦斯抽采窗口期需要综合考虑开采速度和围压的影响，以及不同区域抽采负压的合理分配，以实现煤层气的高效抽采。
