ON SITE
Koos Jordaan, executive director and technical director at Master Drilling (centre) with
mining analyst Peter Major, director of Mining at Mergence corporate solutions (left)
and Leon Louw, editor of Plant Equipment & Hire and African Mining (right).
According to Jordaan there are a lot of
similarities between the shaft boring, tunnel
boring and raise boring – where the machine
cuts rock in a circular path and then crushes
it. The first question when excavating a
blind shaft, is of course, how to remove
and lift the material. “To solve the problem,
we decided to drill the blind end at a small
diameter and follow it with a larger diameter
drill which means less material to get rid of.
The bulk of waste material is fed via gravity
into a kibble,” explains Jordaan.
At the bottom of the shaft borer is the
boring machine which includes the cutter
head and a massive gearbox. The boring
machine basically crushes the rock with
brute force, moving up and down. The
cutter head excavates the blind sink and
the gearbox drive splits energy between
the pilot and the reaming section, which
consists of grippers similar to that found on
Master Drilling’s Tunnel Boring Machine (the
Tunnel Boring Machine excavates horizontal
tunnels and can be used in a number of
mining and construction applications).
A worm down a shaft
Master Drillings’ revolutionary shaft borer and vacuum system.
Faster, safer and cheaper
“We believe that if you can bore
something it’s a lot better than blasting
it,” says Jordaan, whose team has been
at the forefront of developing technology
with the aim of disrupting the shaft
sinking and tunnel boring industries. “In a
world where energy efficiency, pollution
and global warming are becoming
prominent issues, we need to do things
more sustainably, smarter, better and
more effectively, adds Izak Bredenkamp,
group business development manager
at Master Drilling. “An increasing global
population will continue demanding
resources like minerals, fuels and metals.
This means that mining companies have
to reach ore bodies quicker, safer and
more cost effectively than what they have
been able to do in the past, and that is a
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JANUARY/FEBRUARY 2020
challenge. We want to make sure mining
companies stay ahead of the pack, and
our response is finding ways for them to
get there safer, quicker and faster,” says
Bredenkamp. Master Drilling hopes to
bring the full system to the market within
the next year.
Intricate and unique system
Jordaan explains that the borer will be able
to cater for different diameter shafts from
7.5m to 11.5m wide. It can be used in either
a blind sinking mode, or in conventional raise
bore type applications, where the geology is
not that competent at large diameters. It is
possible for only three or four people per shift
to man and operate the machine once it has
pierced the top ten metres of soil and rock.
An additional 20 plus people will be needed
to perform on-surface general functions.
The grippers and advance system pushes
and pulls itself like a worm down the shaft,
while the reamer head excavates the shaft
and the material drops into a kibble, located
inside the cutter head. Rock cuttings are fed
into this kibble via gravity. The kibble with
the crushed rock is lifted about 50m to the
service stage from where the excavated
material is conveyed to the surface. The
distance between the pilot drill and the
reamer is about 7m. The pilot drill advances
about half a metre before pulling the reamer
head down. Jordaan explains that the short
distance between the drill and the reamer
needs to be maintained to ensure proper
shielding as the area is not supported yet
and is vulnerable to instability. The initial pilot
hole is about four metres in diameter, while
the reamer cuts a shaft of anything from
seven and a half to 11m in diameter.
On the main stage
Four metres behind the boring machine
is the main stage that contains all the
power packs and intelligence. Two to five
people will work in this stage, providing
primary support. A shield structure protects
workers on the stage until they have
installed the required support. While the
machine is busy excavating, the crew
on the stage carries out all the required
support work on the excavated shaft. They
drill nine to 12m long anchors into the wall,
and 2.4m bolts will lend further primary
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