Abstract
In blasting of soft to medium hard rock, the problem of high density resulting in excessive utilization of emulsion explosive is well known. The authors have conducted some experimental blasts to delve into the detonation behavior of conventional blasting and various other explosive consumption reduction techniques which induce air gaps using plastic tubes, plastic bottles or plastic balls in the explosive column. Resistance wire technique is used for gauging in-hole continuous velocity of detonation. The VOD varies from 5321.6 m/s to 4544.2 m/s and from 5123.4 m/s to 4274.2 m/s in conventional site mixed emulsion column and distributed spherical air gap column respectively. The detonation behavior is stable and similar in both these cases. While using plastic bottles or plastic tubes as air gaps, the VOD is fluctuating from 4636.3 m/s to 3268.4 m/s and from 4935.9 m/s to 3362.8 m/s respectively with a collapse of about 12 % from the average VOD of conventional SME column. The VOD falls abruptly when the detonation wave encounters large air gaps but it is successfully travelling through the air gaps making the detonation behavior more capricious.
Highlights
The VOD is a speed at which the detonation wave travels through a column of explosive (Bhandari 1997)
For the purpose of this research in-hole continuous VOD is measured for complete site mixed emulsion (SME) column, SME column induced with hollow plastic tubes, SME column induced with hollow plastic bottles and distributed spherical air gap (DAG) column
The detonation wave which comes across such large air gaps will get more attenuated since relative less amount of explosive is available unlike the DAG column
Summary
The VOD is a speed at which the detonation wave travels through a column of explosive (Bhandari 1997). VOD is an important indicator of the performance of an explosive It is influenced by many factors such as explosive confinement, formulation, sensitizing agents, density, diameter of borehole, primer type and size, sleep time in borehole, dynamic desensitizing effects, blast environment, drop impact in borehole, temperature, borehole loading technique, blast design, length of explosive column, storage, transportation, mixing in bulk loading system, manufacturing etc. In this technique air decks are introduced using wooden or plastic spacers with diameter equivalent to the borehole diameter, resulting in a complete non explosive zone inside the charge column This technique is generally not preferred in holes of 9-10 m depth as it is a time consuming process, which requires more physical labor. In this paper the detonation behavior of DAG blasting is studied and a comparative evaluation of this novel technique is presented for detonation behavior of the explosive column resulted due to conventional site mixed emulsion (SME) technique, plastic tube technique and plastic bottle technique
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