UNDERGROUND DRILLING_proof 25/05/2016 10:08 Page 1
UNDERGROUND DRILLING
Drilled metres
angled. These different directions can mean you
may have to choose a different matrix for your
core bit. In some drilling conditions, when
drilling an up hole, you may need to change the
matrix you would normally use in a downhole
and go one series higher. For example, if you
were drilling in a downhole with a Hero 9, you
would have more weight on the bit du e to the
rod weight. Once you are drilling in an up hole,
the rod weight would be gone and you would
need to compensate with a softer matrix found
in a higher series, such as a Hero 11. Higher
series core bits have softer matrices that allow
the diamonds to expose more easily. This means
that the core bit stays sharper even without the
‘weight on bit’ pressure required.”
Paul Moore spoke to players
in four areas of underground
drilling, covering
exploration, development,
production and bolting,
covering new machines,
approaches and strategies
tarting with underground diamond drilling
for exploration, it is similar to its
counterpart on the surface but Fordia
argues that there are still some differences that
need to be considered. These differences can
play a role when it comes time to choose drilling
equipment.
“Underground drilling involves definition
drilling and the focus is on production and
speed - you do not want to slow down the
extraction part of the operation. Given this
focus, achieving the best rate of penetration is
important. A core bit that can cut rock well and
has good rotation speed can provide a better
rate of penetration. “
Fordia recently launched a core matrix that is
ideal for underground drilling. The RockStar is a
series 10 matrix that is very versatile, adapts
well to variable grounds and offers good
S
The Fordia
RockStar 10 is
described as an
ideal choice for
smaller diameters
such as BTW and
LTK48, as well as
NWL2, making it
well-suited for
underground
drilling
86 International Mining | JUNE 2016
The Simba S7 production drill completes the
range of Simbas and Atlas Copco believes that
there is now a Simba model “to fit all mining
applications.”
Lower powered drill rigs
resistance to rock abrasiveness. “It is a great
self-sharpening matrix that works well with less
powerful drill rigs.” The RockStar 10 is described
as an ideal choice for smaller diameters such as
BTW and LTK48, as well as NWL2, making it
well-suited for underground drilling.
Unknown ground versus known ground
Most mines have been in operation for a number
of years so the type of rock will not be a
mystery. Several holes will have already been
drilled so the team will know what to expect and
surprises will be rare. “Drillers will not need to
limit their choices to core bits that are suitable
for a wider variety of ground, but can focus on
bits that have been developed for specific
ground types, such as the Hero series.
Additionally, since you know the type of ground,
you could opt for a higher crown so the number
of times you will need to change the bit will be
reduced.”
In underground drilling, most of the time, the
holes are not as deep, for example 200 m
instead of 1,000 m. This may lead drillers to
choose conventional drilling methods rather
than using wireline drilling methods. The thinner
kerfs found in core bits used in conventional
drilling can lead to a better rate of penetration.
Fordia adds: “In underground drilling the
direction of the borehole can be down, up or
Typically, underground drilling provides less
space for drill rigs so they tend to be smaller
and less powerful. “When drilling with a lowpowered drill rig, especially in an up hole, you
will need a core bit with a softer matrix. As
mentioned above, the softer matrix has
diamonds that are easily exposed and will allow
the core bit to stay sharp, cut well and provide a
good rate of penetration even when using
equipment that doesn’t allow give you the
required feed pressure. “
As mentioned, underground drilling does not
provide excess space. The Elepump KF-50M
from Fordia is a lightweight and smaller model
that can be easily transported by two men. “This
mud pump is ideal for underground drilling or
for any drill rig with limited space. Despite its
size, the KF-50M is a heavy-duty pump that
performs well in extreme conditions and
handles water and all types of specialised
additive mixes, including bentonite and quicksetting cement. Tests with customers have
shown it to require little maintenance – up to
five months without having to perform
maintenance or change parts.”
Fordia concludes: “We all realise that the
choice of drilling equipment is the most
important decision and will have a major impact
on your drilling performance. While the type of
ground is an important factor, other factors are
important to consider when drilling
underground. Be sure to choose a manufacturer
who understands the differences between
surface and underground drilling and can offer
an integrated solution of products developed for
underground conditions, such as underground
core barrels including head assemblies and
overshots, drill rods and other accessories.”