Plasma technology has a potential application prospect in the field of coal seam permeability enhancement. However, the relationship between plasma breakdown energy and the improvement effect of coal pores and fractures is lack of in-depth research. This study proposed a novel method for characterizing the plasma breakdown energy, and three testing techniques, namely, particle size distribution, mercury intrusion porosimetry (MIP) and low-field nuclear magnetic resonance (NMR), were utilized to examine the pore and fracture distribution of coal samples obtained from Jiulong Mine under varying breakdown energy conditions. The influence between breakdown energy and pores and fractures development is revealed. The results show that: (1) The degree of coal sample fragmentation increases with the increase of plasma breakdown energy. (2) Different breakdown energy induced the development of different pore distribution patterns. At lower breakdown energy, an increase in the volume of macropores dominates. As the breakdown energy increases, there is a rapid increase in the volume of mesopores, a slight increase in minipores, and the least increase in micropores, indicating that plasma treatment primarily improves pores with diameters greater than 100 nm. The test results of the three techniques were mutually verified. (3) Compared with capacitance energy and voltage, the effective breakdown energy obtained by the integral method has a more significant linear relationship with the particle size distribution, total pore volume, and average pore diameter, indicating that the effective breakdown energy is more suitable for characterizing the crushing effect of plasma. During the plasma breakdown process, the expansion stress and thermal stress formed by the effective breakdown energy exceeded the local tensile strength of coal, leading to the generation and development of pores and fractures, which in turn led to the rupture of the coal body. The larger the breakdown energy, the larger the crushing circle formed around the ion channel, the finer the coal is crushed, and the more pore fractures are developed. These nascent pores and fractures provide channels for gas transport, which is extremely favorable for coal mine gas extraction. The research conclusions provide theoretical support for the application of plasma in fracturing and permeability enhancement in coal seams.

中文翻译：

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等离子体击穿对烟煤孔隙和裂隙的影响：一种新的击穿能表征方法

等离子体技术在煤层增透领域具有潜在的应用前景。但等离子体击穿能与煤孔隙、裂隙改善效果之间的关系缺乏深入研究。本研究提出了一种表征等离子体击穿能的新方法，并利用粒度分布、压汞孔隙度测定法（MIP）和低场核磁共振（NMR）三种测试技术来检查孔隙和裂缝分布不同分解能条件下从九龙矿获得的煤样。揭示了击穿能与孔隙和裂缝发育之间的影响。结果表明：（1）煤样破碎程度随着等离子体击穿能的增加而增加。 (2)不同的击穿能导致不同的孔隙分布模式的发展。在较低的击穿能下，大孔体积的增加占主导地位。随着击穿能的增加，介孔体积迅速增加，微孔略有增加，微孔增加最少，表明等离子体处理主要改善直径大于100 nm的孔隙。三种技术的测试结果相互验证。 (3) 与电容能量和电压相比，积分法得到的有效击穿能量与粒径分布、总孔容、平均孔径具有更显着的线性关系，表明有效击穿能量更适合表征等离子体的破碎效果。等离子体击穿过程中，有效击穿能形成的膨胀应力和热应力超过煤体的局部抗拉强度，导致孔隙和裂隙的产生和发展，进而导致煤体破裂。击穿能越大，离子通道周围形成的破碎圈越大，煤被破碎得越细，孔隙裂隙越发育。这些新生孔隙和裂缝为瓦斯输送提供了通道，对煤矿瓦斯抽采极为有利。研究结论为等离子体在煤层压裂增透中的应用提供了理论支撑。