Research on the Effects of an Electrode Drill Bit during the Rock Drilling Process by High-Voltage Electric Pulse

High-voltage electric pulse rock-breaking (HVEPB) has proved to be a novel and inexpensive method of breaking rock regardless of rock composition, but the design of the electrode drill bit lacks a theoretical basis. In this paper, we first establish a plasma channel model for electric breakdown and a numerical rock-breaking model for HVEPB, which can simulate the rock electrical breakdown plasma channel and the effect of different electrode drill bits on HVEPB. Second, we analyze the effects of different electrode arrangement structures and high-voltage electrode angles on plasma channels and the effects of internal cracks and rock-breaking processes through numerical simulation. Finally, we describe HVEPB experiments conducted using electrode drill bits with different electrode arrangement structures and high-voltage electrode angles, and with the boreholes reconstructed in three dimensions to analyze the effects of different electrode arrangement structures and high-voltage electrode angles on HVEPB drilling. The results show that the effects of the electrode drill bits on HVEPB are reflected mainly in the difference between the plasma channel and shock wave. Different electrode arrangement structures and high-voltage electrode angles result in different electric fields and energy utilization efficiencies within the rock, resulting in different shock waves and differences in the depth, shapes, and penetration of the plasma channels. The simulations and experimental studies in this paper can guide and optimize the design of the discharge tool to upgrade the drilling efficiency of HVEPB.