Study on the Effect of Blast Delay Time Between Blastholes in Sublevel Caving

Reasonable delay time between blastholes is imperative in improving the blasting effect and mining efficiency. At present, the research findings on the effect of inter-blasthole delay time in sublevel caving are sparse. In this study, the effects of different delay times between blastholes in sublevel caving were studied through numerical simulation and field tests. The results show that the fractal dimensions of the crushing zones and fractures between the blasthole decrease with the increasing delay time between blastholes; the longer the delay time, the more suppressed the blasting effect. The peak stress of short time delay between blastholes is larger than that for long time delay between blastholes in the range of the blasted room, which is conducive to rock fragmentation. Further, the peak stress field between unexploded blastholes with a short time delay is smaller than that for a long time delay, which helps protect brow lines. Thus, the short delay between blastholes can effectively protect the rear eyebrow line in field applications and improve mining efficiency.