Background Plasma channels serve as key pathways for energy transfer and play a central role in electrical pulse rock fragmentation. Factors governing their evolution include the charging voltage of the pulse capacitor, discharge electrode spacing, and electrode type, among others. However, plasma channel evolution under different combinations of discharge parameters remains unclear.

Purpose This study aims to clarify, through experiments and simulations, the effects of two key parameters, namely the charging voltage of the pulse capacitor and electrode spacing, on plasma channel evolution, and to quantify the relationships between key discharge parameters and rock fragmentation performance.

Methods A comprehensive experimental platform for electrical pulse rock fragmentation, incorporating optical imaging with high spatial and temporal resolution, was developed. Granite samples were subjected to 20 repetitive discharges under each of three discharge parameter combinations (350 kV/3 cm, 350 kV/5 cm, and 300 kV/3 cm). Optical images of the plasma channels, channel length, and fragmentation volume were acquired and analyzed. Quantitative analyses were also conducted using a plasma channel impedance model.

Results The results showed that, at a charging voltage of 350 kV and an electrode spacing of 3 cm, the plasma channel initiated at the electrode tips, propagated through the rock, and bridged the high-voltage and ground electrodes. Its optical emission intensity gradually increased as electrical energy was delivered by the circuit, began to decrease after 13.15 μs, and continued to decay until arc extinction. Both increasing the charging voltage and increasing the electrode spacing enhanced the optical emission intensity of the channel and improved rock fragmentation performance. Specifically, a higher charging voltage shortened the channel formation time, whereas a larger electrode spacing partially inhibited channel development. Under a given discharge parameter combination, the channel length increased approximately linearly with the number of discharges, while the fragmentation volume increased continuously. Analysis using the plasma channel impedance model further showed that increasing the charging voltage from 200 to 400 kV increased the channel radius, shock-wave intensity, and internal energy. The model predictions agreed with the experimental trends.

Conclusions These findings clarify how charging voltage and electrode spacing affect plasma channel evolution, and provide a theoretical basis for optimizing the parameters of electrical pulse rock fragmentation systems and improving rock fragmentation performance.