SHAFT SINKING
DMC Mining has recently expanded its
raisebore and box hole drill fleet with
Herrenknecht rigs in Chile
Jordaan expanded on the next stages of the
SBS’ development: “It will be optimised in Phase
2-4 (manufacturing-commissioning). Some
design/aim changes will be made, but there will
be no major changes for the part of the
machine/system that was tested. Most of the next
phase is about completing and commissioning the
system.”
With a third party verifying the three key
performance indicators Master Drilling set out for
the SBS had been completed – exceeding an
advance rate of 500 mm/h, testing the machine’s
cutting ability on both wet and dry material, and
hitting designated penetration rate and
revolutions per minute metrics – the company is
well placed to move into this new phase.
COVID-19 has changed the direction, though.
“We decided to stop capital expansion projects
due to the COVID-19-related uncertainty for the
short term,” Jordaan explained.
“Our expectation is to get approval from Master
Sinkers (a Master Drilling subsidiary)
shareholders for phase 2-4 of a now smaller
diameter concept that was engineered during
resetting the strategy in the first half of 2020.”
The new scope encompasses a 4 m diameter
sinking configuration, which would be
commissioned on a 50 m sink and resourced for
shorter shafts to save cost, according to Jordaan.
“The system will work in the same manner for a
deeper shaft of say 1,500 m but would need
different capacity surface infrastructure for specific
projects,” he said.
He added: “Our approach now is to construct
non-critical, smaller infrastructure with lower
cost/risk, prove the system and then be able to
scale the same concept up to larger/deeper
shafts. We expect that this approach will be more
progressive/constructive and receptive to client
risk management.”
Out for a raise
Outside of the SBS, Master Drilling is helping
mechanise the shaft sinking sector in another way.
Like Cementation (see High Profile on page 78),
it has used wide diameter raiseboring technology
to help sink shafts that already have bottom
access.
It recently completed the pilot drilling of
a circa-1,400 m length hole at the Northam
Platinum Ltd-owned Zondereinde mine’s
western extension, in South Africa.
The successful completion of the
Number 3 Shaft pilot hole at 1,382 m
length is a world record, according to the
company, with the previous record being a
1,070 m shaft drilled in 2012 at Lonmin’s
K4 mine.
This recent hole was sunk for an access
shaft application at the operation, with
reaming at 4.8 m diameter due to
commence soon, according to Jordaan.
“The pilot drilling was done to a very
high tolerance with new directional drilling
technology tooling acquired by Master
Drilling,” he said. “Significant was the way
fissures were sealed at depth with the
methodology developed through previous
experiences.”
Jordaan said Master Drilling has seen
an increase of enquiries in raiseboring for
shaft sinking activities due to the
company’s experience and expertise of completing
such challenging work.
“We are considering scopes of up to 10 m
diameter over short depths/good geology and
deep single lift shafts up to 2,400 m deep,” he
said of the potential shaft sinking work the
company could carry out with raisebore
technology.
Ken McIntyre, Manager SBR Program at DMC
Mining, which has recently bolstered its own
raiseboring fleet with new Herrenknecht
equipment, also thinks there is space in the
mechanised shaft sinking environment for
raiseboring.
“Raiseboring certainly has its benefits when
shaft bottom access is available,” he said.
“We are seeing constant developments in
raiseboring rigs to drill deeper and ream larger
diameters. Depending on project parameters, both
(raiseboring and the SBR) are viable options for
migrating away from solely relying on drill and
blast methods.”
Jordaan expanded on the specifics of applying
such technology: “Raiseboring is the lowest cost
alternative to conventional shaft sinking to a
considerable degree. The challenges for some
projects are stand-up times of shaft sidewalls in
certain geologies/sizes that require a different
approach, as well as underground access required
for raiseboring.”
Even with such challenges in place, those
specialised in the shaft sinking sector are finding
more and more solutions that remove personnel
from harm’s way and move the industry a step
closer to viable mechanisation.
Now all that is needed are some more miners
willing to test such solutions.
IM
Master Drilling says the successful completion of
the Number 3 Shaft raisebore pilot hole at 1,382 m
length is a world record
SEPTEMBER 2020 | International Mining 75