Investigation into methods to identify and accurately locate misfired explosive charges following drill and blast operations

Abstract

Drill and blast tunnelling typically requires firing scores of explosive charges in a predefined sequence and from time to time, an explosive charge will fail to detonate, or will fire out of sequence; this event is known as a misfire. This research investigated a variety of techniques to reliably detect and accurately locate explosive misfires following drill and blast operations. Previous related investigations into blast monitoring aimed to optimise the blasting process and fragmentation, or to minimise the environmental impact of tunnelling operations. In contrast, this research focused on spatially locating an individual shot by utilising its unique blast induced impulse signature. Acoustic signal detection and analysis have been employed to uniquely identify the impulse point of origin. Signal classification was carried out on low energy and high-energy impulses from tunnelling/mining operations. Initial results have shown that even using an individual sensor, it is possible to discriminate between impulse origin locations as acoustic paths increase from millimetre-scale to meter-scale. We have shown that, in steel reinforced concrete beams and slabs and in natural rock mass, multiple impulse signals, made at same position, correlate strongly, but impulses originating from different positions showed significantly reduced levels of correlation. We found that higher energy impulse signals generated by small explosive charges, in contrast to mechanically induced impulses, also exhibited strong correlation. Significantly, early experimental results have shown a strong correlation between low energy impulses and high-energy impulses originating at the same location during blasting in natural rock. This opens up the possibility to establish a methodology to classify impulse origins and thereby to potentially identify the locations of misfires.

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Identifiers

ORCID for Matthew Wright: orcid.org/0000-0001-9393-4918

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