Understanding Vibrations from Multihole Blasts Using Short Delay Periods


Distributing charge weight linearly, such as in a long borehole, encourages the enhancement of a lower spectrum of vibrations. The effect of the ground on the frequency spectrum of a blast is to selectively filter the vibrations with distance such that the grounds resonant frequencies, which are in the low frequency range, predominate with distance. The net effect of this is to result in blast vibrations of lower overall frequency with increasing monitoring distances. The predominant difference in monitored blasting vibrations from construction, quarrying and surface coal mining operations is a direct function of the operation size. This dictates both the length of charge used and the distance of the monitoring station from the pattern (i. e. large sinlge charge weights cannot be used in close proximity to dwellings. ). Blasting vibration levels for multi-delay blasts can be reduced and thus the potential for damage reduced (Rein and Thomas, 1985) by increasing the delay period value.


Mining and Nuclear Engineering

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© 1986 International Society of Explosives Engineers (ISEE), All rights reserved.

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