Investigation to Determine the Origin of Air Overpressure from Quarry Blasting
Previous researchers have put forward two different theories as to the origin of air overpressure from quarry blasting. In 1980, Siskind et al. postulated that the initial face movement gave rise to the displacement of air and that this resulted in the air overpressure pulse. However in 1990 McKenzie et al. carried out research that indicated that the air overpressure pulse came into being as consequence of the shock wave created by the detonation of the explosive charge in a blast hole, rapidly propagating through the rock and then impacting on the quarry face. In an attempt to evaluate these opposing hypotheses, an investigation was undertaken over a 4-year period with the aim of determining the precise origin of air overpressure. The research was carried out at a chalk quarry in the North of England. The choice of this particular location was made on the basis that the rock type is very homogeneous with no discontinuities and the quarry operator carries out small full scale single row blast (typically five holes per blast). Thus a series of tests using single row fully instrumented full scale quarry blasts were carried out. The components that were assessed and investigated were the air blast arrival times in front of the face, the initial movement of the blast face, the precise initiation times of each blast hole, the speed of sound in both air and the rock host and an attempt was made at timing the development of the peak gas pressure within the blast holes. The investigation indicated that the event (within the blast mechanism that is the source of air overpressure) always occurred sometime after the Shockwave had impacted the face but on average before initial face movement. This lead to the conclusion that it was most likely that the transmission of gas through the face, created from the detonation of the explosive charge was the source of air overpressure. However it must be borne in mind that these air overpressure experiments have only been carried out on one specific rock type.
W. J. Birch et al., "Investigation to Determine the Origin of Air Overpressure from Quarry Blasting," Journal of Explosives Engineering, vol. 31, no. 1, pp. 32-39, International Society of Explosives Engineers (ISEE), Jan 2014.
Keywords and Phrases
Air blast; Air overpressure; Arrival time; Blast holes; Explosive charges; Most likely; Quarry operators; Rock types; Blasting; Detonation; Research; Rocks; Quarries
International Standard Serial Number (ISSN)
Article - Journal
© 2014 International Society of Explosives Engineers (ISEE), All rights reserved.
01 Jan 2014