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Airblast-overpressure Levels from Confined Underground Protection Blasts.
NTIS: PB 205 501 :24 pages
The Bureau of Mines recorded and analyzed overpressure levels for three production blasts at the White Pine Copper Mine, upper Michigan, to obtain representative data from single-heading blasts in a long, straight haulageway and to estimate the damage potential inherent in production blasts fired in close proximity to underground structures. Commercial pressure gages with a flat response to 1 khz were used with an fm tape recorder to record the overpressures from one dynamite and two ammonium nitrate-fuel, oil, 500-msec production blasts having zero-delay charge weights of about 75 lb (34 kg). The recorded waveforms from the underground blasts (1) were more complex than the typical free-air wave, (2) were of larger duration, and (3) had numerous secondary arrivals owing to reflections from the ribs and roof. The waveforms showed that the zero-delay charges produced the only high overpressures.
IH; Report of Investigations
NTIS Accession No.
NTIS: PB 205 501
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division