Mining_Methods_UnderGround_Mining - Mining and Blasting

Slot drilling at Ferbasa: The Simba M6 C in action and, (right), the perfectly finished row of holes.
rigs equipped with COP 1238ME rock
drills, which drill 6,000 m/month to
achieve a productivity of 22 m/h. The
mine also has a Promec M195 pneumatic
rig equipped with COP 131EL
rock drill. These machines are also used
to drill orebody definition holes, and
achieve 3,500 m/month.
Slot drilling
One of the main challenges at Ferbasa’s
underground operations is the development
of inverse drop raises. These openings,
which are also called ‘blind raises’
because they don’t communicate with
the upper level, can only be accessed
from the lower level. This limitation is
dictated by the mining methods.
Previously these blind raises were developed
upwards by successive individual
The slot drilling crew with their Simba.
advances of up to 6 m. Nowadays, this
practice has been replaced with a fully
mechanized method, increasing the
speed and safety of drilling the openings.
Looking for a solution to improve
operator safety when drilling these production
raises, technical personnel from
Ferbasa visited LKAB’s Malmberget
iron ore mine in Sweden, where they
studied the development of inverse drop
raises blasted in one single shot. After
the visit, Ferbasa started employing a
slot drilling technique, and Ipueira and
Medrado are now the most experienced
mines in Brazil in its use. Slot drilling
requires a row of 7.5 in -diameter inter-
connected holes to be drilled using a
special guide mounted on a regular ITH
drill hammer. Thus, with an available
free face, drilling accuracy, and controlled
blasting techniques, openings
CaMPO FOrMOSO, Brazil
of up to 25 m length are successfully
achieved. The main advantages of the
method are personnel safety and speed
in the drilling. Also, slot drilling is
more precise and, in general, more
productive.
A Simba M6 C drill rig equipped with
COP 64 DTH hammer and ABC Regular
system, as well as an on-board booster
compressor, has been acquired for drilling
inverse drop raises with holes up to
10 in-diameter. Depending on the length
of the raise, and the quality of the rock
mass, the slot drilling technique is used.
If the length of the raise is short, and
the rock quality poor, the traditional
technique with reamed holes is used.
Until the Simba M6 C arrived, Ferbasa
was carrying out slot drilling with
only one machine. They chose the new
Simba rig because of its advanced technological
and safety features. One of the
main advantages is the setup, which
only has to be carried out once at each
site.
The Simba M6 C machine is also easy
to operate, and the spacious, air-conditioned
cabin is an attractive feature.
The mine spent five years looking for
a solution to the opening of inverse drop
raises, and is pleased with its investment
in technology and modernization
represented by the Simba M6 C.
acknowledgements
Atlas Copco is grateful to the managements
at both Ipueira and Medrado
mines for their contributions to this
article.
underground mining methods 131