Effect of discharge voltage on crack distribution and fracture extent in multi-hole pulsed discharge rock fragmentation

This study investigates the effect of discharge voltage on fracture distribution and fragmentation extent in multi-hole pulsed discharge rock fragmentation. Comparative experiments were conducted on red sandstone specimens across 5 voltage levels ranging from 50 kV to 90 kV (in 10 kV increments). Rock damage surfaces were quantitatively characterized in terms of crack density, fractal dimension and damage variable through specimen cutting, staining and crack image processing. Numerical simulations were conducted using the LS-DYNA finite element analysis software to analyze the crack propagation process within the rock mass during dual discharges and the effect of the second discharge (at varying voltages) on pre-existing cracks induced by the first discharge. Results indicate that increasing the discharge voltage from 50 kV to 70 kV led to a 54.5 % increase in crack density, a 6.4 % rise in fractal dimension, and a 67 % increase in the damage variable. However, further voltage increases beyond 70 kV resulted in stabilization of these 3 metrics rather than continued growth. At higher discharge voltages, the second discharge triggered secondary propagation of damage initially caused by the first discharge.