Growth mechanisms of electrical breakdown channel in electro-pulse-boring under external strong magnetic fields

Abstract

Electro-Pulse-Boring (EPB) generates electric breakdown channels in dielectric media to achieve efficient rock fragmentation for deep energy resource development. Strong magnetic fields have been shown to enhance the longitudinal penetration of plasma channels; however, the effects of magnetic-source position and field intensity on breakdown trajectory remain unclear. In this study, a numerical model called Rock Electrical Breakdown under Strong Magnetic fields model is established based on the solid-insulation breakdown theory, Kirchhoff's voltage law, and Maxwell's equations. The model is used not only to investigate how plasma channels initiate, propagate, and penetrate under different magnetic-field orientations, spatial positions of the magnetic source, and intensity of the external magnetic field but also to clarify how magnetic forces govern channel growth. The results indicate that the magnetic forces significantly promote the longitudinal development of the plasma channels. By adjusting the orientation of the magnetic field, the trajectory of the channel can be effectively controlled, thereby enhancing the performance of EPB. The axial distance between the magnetic source and the rock is identified as a key parameter that determines the distribution of the magnetic field within the rock, with the maximum extent of rock damage occurring at 6–8 mm. Moreover, increasing the intensity of the external magnetic field further accelerates the longitudinal extension of plasma channels and enhances the overall efficiency of EPB. This study may provide theoretical support for EPB technology assisted by strong magnetic fields.