Rock cutting excavation technologies and particularly continuous
excavation technologies, can offer benefits in the areas of reduced costs,
higher revenue and increased safety in a variety of mining situations.
Non-explosive rock excavation technologies for example, can deliver
significant benefits in the areas of dilution and improved ground support
(no overbreak). This paper is an attempt to focus on the development and
future of alternative rock breaking technologies and to provide some
insights as to why and how we should proceed in this direction. The
market size for underground hard rock excavation technologies is
examined. A short review of the evolution of various rock excavation
technologies in terms of cost and production rate is given and a summary
of the state-of-the-art technology is presented. Mechanical excavation
technologies (TBM) have very high production rates compared to D&B
and the gap is widening, however, they have not been successfully
applied to mining applications. Operating costs for mechanical and D&B
systems have been dropping over time, however, D&B costs are the
lowest. Given the current state of knowledge it appears that with regard
to hard rock underground metalliferous mining that R&D efforts should
be focussed in the following areas - disc cutter tool development
(materials and design; operation; presentation to the rock surface), hybrid
cutting systems (consisting of water jets and disc cutters) and
development of pressurised hole breakage technologies. It is also
possible that two techniques known as the pulsed laser and pulsed water
jets may have some potential. The generally agreed specifications for a
widely applicable underground hard rock excavating machine are - disc
cutter based, a minimum production rate of 100 t/h, be flexible,
manoeuvrable and deployable, weight of less than 100 tonnes and be
economically competitive with D&B in rocks over 150 MPa UCS. Such
a machine would seriously challenge the position of conventional D&B in
a wide range applications and provide some of the benefits of
mechanisation and automation that the mining industry is pushing so hard
for. However, technology developments in the D&B area are not static
and hence the target is moving and is increasingly difficult to overtake.