Overbreak Control in the White Pine Underground Mine.
Fletcher-LR; Plis-MN; Stachura-VJ
Paper in Proceedings of the 15th Conf on Explosives & Blasting Tech New Orleans Louisiana 1989 :11 pages
Falls of ground remain a leading cause of fatalities and injuries in underground mines. In response to this situation, the Bureau of Mines conducted a series of experiments in the White Pine room-and- pillar copper mine that resulted in smoother, safer ribs due to a reduction in the amount of overbreak caused by blasting. The tests evaluated the effects of changes in the loading of the rib holes of the mine's 20-by 28-ft drift round driven in shale and sandstone. The relative integrity of the ribs remaining after the blasts was measured using both photographic and seismic rrefraction techniques. Four variations of the mine's standard blast design were examined. Comparisons were made between rounds with rib holes having fully coupled and decoupled powder columns that were initiated by millisecond- and half-second-delay caps. The results showed that the smoothest and most stable ribs were produced by rounds whose rib holes had decoupled powder columns initiated by millisecond-delay caps.
Paper in Proceedings of the 15th Conf. on Explosives & Blasting Tech., New Orleans, Louisiana 1989