The influence of pore characteristics on rock fragmentation mechanism by high-voltage electric pulse

Abstract

Abstract High-voltage electric pulse (HVEP) is an innovative low-energy and high-efficiency technique. However, the underlying physics of the electrical breakdown within the rock, and the coupling mechanism between the various physical fields involved in HVEP still need to be further understood. In this study, we establish a 2D numerical model of multi-physical field coupling of the electrical breakdown of porous rock with randomly distributed pores to investigate the effect of pore characteristics (porosity, pore media composition) on the partial electrical breakdown of rock (i.e. the generation of a plasma channel inside the rock). Our findings indicate that the generation of a plasma channel is directionally selective and extends in the direction of a weak electrical breakdown intensity. As the porosity of the rock increases, so does the intensity of the electric field in the ‘electrical damage’ region—the greater the porosity, the greater the effectiveness of rock-breaking. As the fraction of pore fluid (S water/S air) gradually declines, the generation time of the plasma channel decreases, and the efficacy of rock-breaking by HVEP increases. In addition, in this study, we conducted an indoor experiment utilizing an electric pulse drill to break down the rock in order to recreate the growth mode of the plasma channel in the rock. Moreover, the experimental results are consistent with the simulation results. In addition, the development of this type of partial electrical breakdown is confirmed to be related to electrode polarity and pore characteristics via the experiment of the symmetrical needle-needle electrode arrangement, which further demonstrates the mechanism of partial electrical breakdown. This research is significant for comprehending the process of electric impulse rock-breaking and gives theoretical guidance and technological support for advancing electric impulse drilling technology.