High-voltage electric pulse drilling (HVEPD) is a promising technique for deep hard-rock drilling due to its controllable energy release and environmental advantages. To improve its drilling efficiency in hard formations and to clarify the evolution of electrical breakdown channels in rocks under high-voltage loading, an integrated HVEPD experimental system was developed, and a numerical model incorporating rock heterogeneity was established based on Maxwell’s equations, heat conduction, and electrical breakdown damage theory. Rock-breaking experiments and numerical simulations were conducted on granite and sandstone using different electrode geometries and pulsed electrical parameters. The results show that electrical breakdown channels preferentially propagate along pores, microcracks, and mineral phases with higher dielectric constants, forming irregular tree-like patterns within the rock. The optimal voltage ranges were identified as 110–140 kV for conical electrodes and 230–260 kV for pentagonal prism electrodes. Owing to its stable non-tip discharge behavior, the cylindrical electrode exhibited approximately 10% higher rock-breaking efficiency than the triangular prism electrode and is recommended for granitic hard rocks. In addition, a damped oscillation of the load voltage was observed during electrical breakdown, leading to energy dissipation. These findings provide guidance for parameter optimization and electrode design in HVEPD applications.
Zhu et al. (Mon,) studied this question.