Explosives utilization at a Witwatersrand gold mine
M Gaula
Gold bearing deposits of the Witwatersrand basin are generally less than
2m thick and require conventional narrow-reef mining methods for
extraction and employ explosives as a means of rock breaking. Optimal
utilization of explosives is dependent on the overall design of the blast. The
under-utilization of explosives arises when shot-holes are drilled inconsistently,
overcharged, and when tamping is absent. This can be rectified by
emphasizing the importance of good drilling practices as part of induction
programmes and refresher courses. The project was aimed at determining
whether or not explosives are being optimally utilized at project site. This
was investigated through a study of the properties of explosives, mine
standards, and recommendations for usage. Underground observations
were made to determine whether or not mine standards were being adhered
to. Historic data was obtained to establish the historic relationship existing
between the quantity of explosives used (kg) and the production output
(m2). This was then compared to the quantity of explosives the mine
expects to use per unit of production. The results obtained were analysed to
determine the presence and extent of over- or under-utilization. It was
found that explosives are being under-utilized at the mine. More explosives
are ordered than expected per unit of production. The explosives’ properties
are not thoroughly exploited during blasting, thereby requiring the use of
more explosives than prescribed.
Keywords: blasting practices, explosives utilization, blast design.