Plasma based on electrical discharge has attracted extensive attention in various fields for cracking hard coal, yet the behavior characteristics of plasma channels and the evolution law of fractures in coal have not been investigated in depth. In this study, the evolution law of plasma-induced fractures in coal was revealed by means of physical experiments and numerical simulations. Moreover, the propagation behavior of plasma channels in coal was analyzed. The main conclusions were drawn as follows. The propagation of fractures in coal manifests four behavior characteristics due to numerous minerals and pores in coal bodies: 1) Newly formed fractures are interconnected and develop towards primary fractures; 2) Mineral enrichment areas have an attraction effect on fractures; 3) Fractures propagate along interfaces between minerals and coal matrix; 4) Fractures penetrate through minerals. Besides, the development law of plasma channels in coal under different voltage conditions was explored based on the WZ (Wiesmann H J and Zeller H R. A.) breakdown model of solid dielectrics. It was found that plasma channels in coal develop from the positive electrode to the negative electrode in a “dendritic” shape. The influences of pores and pyrite in coal differ significantly on the patterns and development trends of electrical branches. Specifically, pores in coal have an attraction effect on electrical branches. This indicates a sudden increase in the electric field intensity around fractures, which leads to a surge of local stress and thereby induces the generation of fractures. The research findings are of crucial significance for theoretical study on the propagation mechanism of plasma-induced fractures in coal.

中文翻译：

---

多孔介质材料中等离子体诱导裂缝的演化规律——以煤样品为例


基于电火花的等离子体在裂解硬煤方面引起了各个领域的广泛关注，但等离子体通道的行为特征和煤中裂缝的演化规律尚未得到深入研究。本研究通过物理实验和数值模拟揭示了等离子体诱导的煤裂缝演化规律。此外，还分析了等离子体通道在煤中的传播行为。主要结论如下。由于煤体中矿物和孔隙众多，煤中裂缝的扩展表现出四种行为特征：1）新形成的裂缝相互连接并向原生裂缝发展;2） 矿物富集区对裂缝有吸引力;3） 裂缝沿矿物和煤基质之间的界面传播;4） 裂缝穿透矿物。此外，基于固体电介质的 WZ （Wiesmann H J 和 Zeller H R. A.） 击穿模型，探讨了不同电压条件下煤中等离子体通道的发展规律。研究发现，煤中的等离子体通道以“树枝状”形状从正极发展到负极。煤中孔隙和黄铁矿对电枝格局和发展趋势的影响差异显著。具体来说，煤中的孔隙对电分支有吸引力。这表明裂缝周围的电场强度突然增加，从而导致局部应力激增，从而诱发裂缝的产生。研究结果对等离子体诱导裂缝在煤中扩展机制的理论研究具有重要意义。