In the process of coalbed methane (CBM) extraction, coal seam penetration modification is frequently subjected to several cycle impact due to drilling-blasting method and deflagration fracturing method. Therefore, the split Hopkinson pressure bar (SHPB) was utilized to investigate the impact cycle effect and confining pressure effect on dynamic behavior of coal. Furthermore, the low-field nuclear magnetic resonance (NMR) was utilized to evaluate the modification of multiscale pore before and after 5 cycles impacts. Finally, the 3D profile scanner was utilized to quantify fracture surfaces and assess fracture roughness variation. The results showed that there existed the 6 MPa critical confining pressure that altered the dynamic mechanical properties of coal. Due to the combined effect of the confining pressure and cycle impact, the damage variable based on the energy method showed a log-normal distribution. With increasing strain rate, the micropores evolved into mesopores and macropores. There was a critical strain rate that caused the ratio of effective porosity to total porosity to shift from increasing to decreasing. Furthermore, the fracture roughness was shown to be positively correlated with the ratio and negatively correlated with seepage fractal dimension. The research findings can provide theoretical guidance for the safer and more efficient CBM exploitation.

在煤层气开采过程中，由于钻爆法和爆燃压裂法，煤层渗透改造经常受到多次循环的影响。因此，利用分体式霍普金森压力棒（SHPB）研究冲击循环效应和围压效应对煤体动力行为的影响。此外，利用低场核磁共振（NMR）评估了5次循环冲击前后多尺度孔隙的变化情况。最后，利用 3D 轮廓扫描仪量化断裂表面并评估断裂粗糙度变化。结果表明，存在6 MPa临界围压改变煤的动态力学性质。由于围压和循环影响的共同作用，基于能量法的损伤变量呈现对数正态分布。随着应变率的增加，微孔演化为中孔和大孔。存在一个临界应变率，导致有效孔隙度与总孔隙度之比从增加变为减少。此外，裂缝粗糙度与该比率呈正相关，与渗流分形维数呈负相关。研究成果可为更安全、更高效的煤层气开采提供理论指导。