Influence of initiation mode of explosives in opencast blasting on ground vibration

Abstract

The measurement and analysis of blast induced vibration is presently more state of the art than ever before. A modern understanding of the basic concepts behind vibration effects can help a beleaguered end user more confident about what their measurement really mean. It is reported that blast conducted with non-electric initiation system enhanced the efficiencies of Heavy Earth Moving Machinery (HEMM) machineries and reduced the reported nuisance of blasting. The developed countries are adopting the third generation of electronic detonators but in India the use of detonating fuse for blast initiation is still in practice. There are number of reasons stated by mine officials for this practice being still followed by mining industry. The one of the important reasons is the price ratio of Nonel tubes and detonating cords/fuse, which is comparatively very high in India in comparison with the other countries. A study was planned to investigate the influence of direction of initiation in the blasthole on ground vibration. The four opencast coal mines were selected for the study purpose. The two blasts at same bench were conducted while keeping all the blast design and explosives parameters such as, burden, spacing, hole depth, hole diameter, charge per hole, charge per delay, total charge in blast round, etc., identical. The explosive make for a set of two blasts were of same manufacture and both the blasts were conducted on same day to avoid the variation in explosive formulation. Blast induced vibrations were monitored at 6–11 locations. The experimental set of blasts includes single hole blasts, production blasts, as well as dragline blasts, performed by only changing mode of initiation, i.e. initiation of booster with detonating cord and with non-electric initiation in the bottom of the hole at floor level while maintaining all other parameters identical. The result indicated that former generated lower vibration levels compared with previous mode of initiation. The reductions in vibrations were observed up to 36·2% by for blastholes of depth >20 m. The minimum reduction of vibration was 8·2% for shorter blastholes depth of 7·5 m.

Keywords

BLASTING INITIATION VIBRATION EXPLOSIVES BLAST VIBRATION

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