Pre-splitting for smooth highwall formation is conducted in around 75 per
cent of surface coal operations within Australia. The CMTE (Centre for
Mining Technology and Equipment) in conjunction with BHPAC (BHP
Australia Coal) initiated a project to look at pre-splitting and to
investigate the notching of blastholes for fracture plane control. The
notching was specifically for pre-split initiation and also for discing of the
toe of the production holes to minimise coal loss from the top of the coal
seam. There are currently a number of factors which are driving the
introduction of new pre-splitting technologies and products. The first is
the ever increasing bench height being employed in strip mines which
require a higher quality wall with less blast damage to maintain stability.
Currently depths of 55 metres are common place with depths of 70 - 80
metres fast approaching. The second factor is the introduction of new
technologies or methods which require a high quality highwall produced,
eg highwall mining. This paper discusses the current state-of-the-art in pre-splitting and the
main issues facing successful pre-splitting in the future. The use of a
blasthole notching technology to promote fracturing along the pre-split
line is also analysed. The review indicates that most pre-splitting
challenges in the future can be addressed through better use and
developments of current drill and blast technology. It is also concluded
that a blasthole notching technique may find niche applications in
improving final walls within a surface coal mine, especially where a high
quality wall is required. The notched blasthole method may also allow
pre-splitting in ground conditions and adverse rock structure which
currently cannot be pre-split by existing technology.