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The Effect of Explosive Type and Delay Between Rows on Fragmentation.
Stagg-MS; Rholl-SA; Otterness-RE
Paper in Proceedings of the 15th Annual Conf on Explosives & Blasting Tech New Orleans Louisiana :14 pages
The Bureau of Mines fired seven test blasts in a 22-ft bench of limestone, screening the material to investigate the influence of explosive type and between-row delays on fragmentation. Four four- hole, single-row test shots were conducted to evaluate dynamite, anfo, emulsion, and a 60-40 emulsion-anfo mix. Three 12-hole shots, with 3 rows of 4 holes, evaluated delays between rows of 24, 36, and 120 MS. Accurate in-hole electronic delays were used, firing within 1.5 Ms of the nominal delay. All seven shots had a 6- to 7-ft burden and 10-ft spacing, with a hole diameter of 3-1/2 in fired on a 12-ms delay between holes in the row. The tests were instrumented with strain gauges grouted in the burden region examining stress wave and gas pressure effects. Fiber optic probes were used to confirm timing and to obtain detonation velocities. The type of explosive had little effect on the coarse-size, plus 4-in material. A slight reduction in the amount of finer size, minus 4-in material did result when the explosive charge was decoupled. The effect of delays between rows was minimal, influencing only the breakup of a massive 2-ft bed located in the stemming region. Strain data were similar to data previously reported, suggesting that fracturing between holes in a row occurred from both stress wave and gas pressure effects.
Paper in Proceedings of the 15th Annual Conf. on Explosives & Blasting Tech., New Orleans, La
Page last reviewed: March 11, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division