Short-delay blasting in underground coal mines.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, IC 9064, 1986 Jan; :1-16
The Bureau of Mines has conducted research to determine whether the total elapsed delay time for blasting bituminous coal in underground mines could be safely expanded beyond the present 500-ms limitation without igniting a methane or methane-coal dust atmosphere. The results indicated that the increase of total delay from 500 to 1,000 ms had no detectable effect on safety relative to incendivity as long as permissible practices were observed in all other aspects. Research was also conducted to evaluate the safety of 18-in hole spacing for delay blasting in coal relative to misfires. For a variety of permissible explosives, misfires were observed for about 50 pct of the holes at 18-in spacing. Based on this observation, the Bureau has recommended that the new regulations prohibit hole spacings of less than 24 inches in underground coal mines. Misfires were also observed for 24-in spacing, but the number of misfires and test shots was too small to support any firm conclusions.
Mine-workers; Mineral-processing; Miners; Mining-industry; Coal-miners; Coal-mining; Coal-processing; Coal-workers; Longwall-mining; Underground-miners; Underground-mining; Room-and-pillar-mining; Explosion; Explosion-damage; Explosion-venting; Explosions; Explosive-devices; Explosive-gases; Explosive-hazards; Explosives
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
NTIS Accession No.
Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, IC 9064