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Design Criteria for Sheathed Permissible Explosive Charge for Open Shooting in Flammable Atmospheres.
MISSING :12 pages
The Bureau of Mines conducted research to evaluate the optimum design for a rock-breaking explosive charge that could be fired unconfined in a gassy or dusty coal mine without the danger of igniting the flammable atmosphere. Charges of various shapes, with and without cavities, were tested in a gallery using 3- by 3- by 1- ft concrete blocks as simulated boulders. For these tests the optimum charge, in terms of cost, weight, and convenience in handling, consisted of a flat 1-1/2-lb charge of permissible explosive seven-eighths of an inch thick and 7 in in diameter encased in a 1/2-in thick layer of fine salt (nacl). This work demonstrated that it should be possible to produce an inexpensive explosive rock-breaker charge that would be safe to use in underground coal mines.
Page last reviewed: March 11, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division