Effect of high-voltage electric pulse stimulation on heated-granite: An experimental investigation

High-voltage electric pulse (HVEP) technology merits further investigation into its potential applications. The effectiveness of using HVEP to induce pre-damage and deteriorate hot dry rock (HDR) was investigated in this study. Different peak voltages of HVEP were applied to heated-granite flake specimens. Furthermore, the influence of temperature on HVEP stimulating granite was investigated. The results show that when the applied peak voltages exceeded 96 kV, through-fracture failure occurred in the heated-granite specimens, with higher voltages producing more complex through-fracture networks. The microcrack density of granite specimens increased from 8.63 mm/mm² to 13.26 mm/mm² when the applied voltage rose from 96 kV to 144 kV. Notably, the difficulty of granite electrical breakdown gradually decreased with the increasing temperature of thermal treatment. Through-fracture failures were observed in all granite specimens heated above 400 °C after three HVEP discharges at 120 kV. The maximum damage caused by HVEP was found within the temperature range of 300–400 °C. Additionally, an escalation in the development of internal pores and cracks as the granite specimen temperature increased was observed by using scanning electron microscopy (SEM), accompanied by an increase in pore size and crack width and depth.