Mining_Methods_UnderGround_Mining - Mining and Blasting

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Schematic of sublevel stoping in a narrow vein using the Simba M6 C to drill down holes.
for drilling the blast holes, and also for
developing 40 m-deep raises between
the levels.
In order to minimize dilution in the
narrowest veins, it was decided to em-
ploy a Simba M6 C drill rig equipped
with a COP 2550 rock drill on production
drilling of downholes in this
narrow vein/sub-level stoping operation.
At the same time, the distance
between levels was reduced to 25 m and
the hole diameter was reduced from 4
in to 3.5 in.
The Rocket Boomer L1 C rigs are used
both for development and production.
Each rig, equipped with a single COP
1838HF rock drill, advances at a rate
of 800 m/month in galleries that are 5
m-wide x 5 m-high. Scooptram ST1020
loaders are used for hauling and transport
during the development of galleries
and ramps.
The Scaletec is used throughout the
mine for preparing faces for loading and
for general roof scaling, mechanizing an
operation that was previously time-consuming
and sometimes dangerous.
The ore is transported to the surface
by conventional 40 t-capacity trucks.
Change for good
The technological changes at Sierra
Miranda have been rapid. In less than
Scaletec in action at Sierra Miranda. Close-up of the Scaletec at work.
a year, the entire mine fleet has been
upgraded to modern equipment. In ad-
dition, the operators have acquired new
skills and the whole team is now focused
on increasing the planned production
levels and on improving risk and security
standards.
Furthermore, productivity has in-
creased beyond all expectations. While
the improvements continue, the mine is
also making every effort to achieve ISO
9000 certification.
At Sierra Miranda Atlas Copco works
in a very proactive way. The fleet is
checked daily for the number of hours
each machine has worked, and the
causes of any breakdowns. It is then
decided which machines will be required
for work over the following few
days, and Atlas Copco makes sure that
they are available. This entails a very
flexible programme of maintenance
and follow-up procedures, which can
change from one day to the next.
At the start of the contract, the mine
stipulated that it required 90% equipment
availability. This took a little time
to achieve while training was underway.
However, once all systems were up and
running, availability increased to its
present level of more than 95%.
acknowledgements
Atlas Copco is grateful to the owner
and management at Sierra Miranda
mine for their assistance with the pre-
paration of this article which first
appeared in Mining & Construction
1-2007.
98 underground mining methods