煤层开采过程中频繁采掘扰动或远场顶板周期性破断会产生多次的震动载荷，震动载荷对于煤样微观孔裂隙结构和宏观力学行为具有重要影响。为探索震动载荷下煤样孔裂隙结构演化特征，选取烟煤煤样，利用霍普金森压杆(SHPB)试验系统开展了多次震动载荷冲击煤样试验，借助低场核磁共振分析仪测试了每次冲击后煤样T₂谱，并通过核磁共振成像(MRI)分析了煤样孔裂隙分布及其损伤演化特征。结果表明，随着震动载荷作用次数增加，煤样峰值应力与动态弹性模量均呈现线性下降趋势，震动载荷冲击效应使得煤样承载和抵抗变形能力显著弱化，因此有必要对煤样孔裂隙演化特征展开深入分析。从T₂谱和MRI信息得出，震动载荷初次作用下煤样总体孔隙体积大幅增加，其中吸附孔体积增高达5.0倍，随着震动载荷持续作用，煤样微裂隙开始连通汇聚形成宏观裂纹，使得渗流孔之间连通性大幅提高，煤样总体孔隙率达到峰值，较煤样原始孔隙率提高约6倍。在煤样受震动载荷损伤、破坏的整个过程中，渗流孔的连通性逐渐提高与改善，其分形维数呈线性下降趋势。通过核磁共振成像揭示了震动载荷对煤样孔裂隙作用机制，结果表明煤样中部区域孔隙最先发育并逐步形成微裂隙，在后续震动波反射、拉伸作用下，损伤破坏区域向两侧逐渐演变直至贯通试样。

Frequent mining disturbance or periodic rupture of far-field roof in coal seam mining will produce multiple vibration loads, which have an important influence on the micro pore-fissure structure and macro mechanical behavior of coal. In order to explore the evolution characteristics of pore-fissure structure of coal under vibration load, the SHPB test system was used to carry out a multiple vibration load impact test on bituminous coal. With the help of low-field nuclear magnetic resonance analyzer, the T₂ spectrum of coal after each impact was tested, and MRI was performed to analyze the law of pore distribution and evolution, and the damage evolution characteristics of coal pore-fissure structure were studied. The results demonstrate that the peak stress and dynamic elastic modulus of coal show a linear decline trend with the increase of vibration load, and the impact effect of vibration load significantly weakens the bearing capacity and deformation resistance of coal, so it is necessary to conduct in-depth analysis on the evolution characteristics of coal pore cracks. According to the T₂ spectrum and MRI information, the total pore volume of coal increases greatly under the first action of vibration load, in which the adsorption pores volume increases by 5.0 times. With the increase of the number of vibration loads, the volume of seepage pores begins to increase significantly, while the volume of adsorption pores remains basically unchanged until the sample is completely destroyed. During the multiple action of the vibration load, the internal damage of the coal body gradually accumulates from the initial point distribution to strip distribution until micro-cracks are formed. With the multiple action of the vibration load, the microcracks of the coal sample begin to connect and converge to form macrocracks, which greatly improves the connectivity between the seepage pores, and the overall porosity of the coal sample reaches a peak value, about 6 times higher than the original porosity. During the whole process of coal body being damaged and destroyed by vibration load, the connectivity of seepage pores is gradually increased and improved, and its fractal dimension shows a linear decline trend. The MRI reveals the mechanism of vibration load on coal pore-fissure, and the results show that the central region of the coal first develops and gradually forms microcracks. Under the action of reflection and stretching of subsequent vibration waves, the damaged areas gradually extend to both sides until penetrating the sample.