Research on simulating coal crack development under high voltage electric pulse stress waves using zero thickness cohesive elements

• Published in: Fuel (Guildford) Vol. 378; p. 132657
• Main Authors: Wu, Jiayao, Jiang, Changbao, Hou, Diandong, Nie, Baisheng, Yan, Fazhi, Wu, Mingyang
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.12.2024
• Subjects: Coal fracturing; Crack development process; High-voltage electrical pulse technology; Stress wave; Zero thickness cohesive elements; High-voltage electrical pulse technology; Crack development process; Stress wave; Coal fracturing; Zero thickness cohesive elements
• ISSN: 0016-2361
• DOI: 10.1016/j.fuel.2024.132657

•Stress wave attenuation causes regional variations in coal fracture patterns.•Developed an FDEM-based model for high voltage pulse coal fracturing.•Higher stress wave attenuation observed near plasma channels.•Quantified how stress wave parameters influence coal fracturing. High voltage electric pulse (HVEP) technology has demonstrated significant potential in enhancing coal seam permeability. However, there is a notable gap in numerical simulation studies that investigate the cracks development patterns in coal under the influence of this technology. In this study, a HVEP coal rock fracturing system was utilized to conduct a physical simulation experiment of coal sample electrical fragmentation. A finite-discrete element method (FDEM) model, incorporating zero-thickness cohesive elements, was developed to simulate the process of stress wave-induced crack propagation in coal, triggered by the plasma channel. The results indicate that over time, the stress wave typically exhibits an initial rapid rise followed by an oscillatory decline. The peak value of the stress wave decreases significantly with distance, stabilizing beyond a propagation distance of 10 mm. Furthermore, the fracturing efficacy of coal by HVEP stress waves is closely linked to specific characteristic parameters: within the range of 75–125 MPa, a positive correlation exists between the stress wave peak and the complexity of the coal crack network. Reducing the stress wave loading rate can increase the crack area to some extent, although excessively slow loading rates may lead to excessive energy dissipation during propagation, which is detrimental to crack expansion. Conversely, when the ratio of β to α ranges from 1 to 100, decelerating the attenuation rate of the stress wave aids in generating stress concentration within the crack zone, thereby facilitating crack propagation. The established numerical model aims to advance understanding of HVEP’s fracturing mechanisms and enhance its application in coalbed methane extraction.