A deep roar, like that coming from a jet airliner’s engines on take-off, and the rattle of broken rock sucked into a large steel drum mark the test site of what could be a quick and safe way to sink a mine shaft.
Mining companies around the world are searching for fresh ways to extract minerals, ranging from changes in water use, hauling rock and finding safer, cheaper, and more environmentally friendly ways of mining.
Digital technology is one aspect of these advances, including automated trucks and surface drills to drive up productivity.
Another is accessing ore bodies more quickly, changing financial models to win board and shareholder approvals for projects that might otherwise not have cleared investment hurdles using conventional methods.
At the 2018 Joburg Indaba mining conference, industry veterans and top CEOs — Chris Griffith and Nico Muller heading the world’s two largest platinum producers in Anglo American Platinum and Impala Platinum respectively, and Peter Steenkamp from Harmony Gold — outlined a future without new deep-level, conventionally operated, labour-intensive mines.
Investors were unwilling to wait a decade or more for a mine to be brought into production and have the associated risks arising from dangerous working conditions that could kill miners.
One of the companies at the forefront of this push is JSE-listed Master Drilling, which is investing heavily in technology to move to mechanical extraction of rock from tunnels and ore bodies in place of traditional drilling and blasting.
Master Drilling has deployed its small mobile tunnel boring machine in an extended test at Northam Platinum’s Eland mine near Brits and the results have so far been heartening, advancing 1m an hour, says Master Drilling CEO Danie Pretorius.
The next big breakthrough will be a shaft-boring machine that can sink shafts in virgin ground three times as fast as conventional methods.
On a dusty field on the outskirts of the neat little town of Fochville, Master Drilling’s global headquarters 70km west of Johannesburg, the first stage of the machine is excavating a 10m deep hole in hard rock to prove the concept. The all-encompassing wall of sound comes from a spinning steel disc 4m in diameter with carefully placed high-carbon steel wheels grinding hard rock.
One of the comments made during a briefing on the machine and a mobile-tunnel borer deployed at Northam Platinum’s Eland mine for its first test in a working mine, was that the minute you went underground on an SA mine you went back 100 years.
While there have been small changes in the way mines are run and some variations on equipment, the system is basically unchanged, with labour-intensive, dangerous, difficult work in confined spaces.
Mining is, at its essence, moving countless tons of rock, breaking them down into dust and extracting minerals. There are many nuances, but it is an earth-moving operation.
Mining in SA remains a drill-and-blast batch operation, something Master Drilling is pushing hard to change with technological advances to introduce drilling machines to bore into rock, quickly and safely creating shafts and tunnels and eventually mining.
“We want to industrialise this machine, basically putting a factory into the shaft,” says Nicol Goodwin, the engineer working on the project.
A study from a mine engineering and construction company indicated where one out of 10 projects was feasible with existing shaft sinking technology, this could be raised to three out of 10 if the shaft could be sunk more quickly and safely, he says.
The shaft-boring machine will look somewhat like a 45m high upside-down bottle of wine weighing 550 tons.
The 4m reamer under test will be the neck of the bottle, drilling a pilot hole by clamping itself to the side of the hole it is sinking and pushing itself into the rock.
Immediately above that section is the shoulder of the bottle, which has another set of angled spinning reamers to widen the pilot hole up to 11m in diameter.
The body of the bottle, lowered into the shaft from headgear, is made of a series of platforms or stages from which the shaft can be clad with wire netting and shotcrete and the large 16-ton kibbles, or buckets, can be handled, moving shattered rock and dust from the reamers below.
The machine will use a team of 30 people against 120 on conventional shaft-sinking projects, with three or four people on the machine at a time.
The machine, which will cost R450m to make, will be ready to deploy early in 2021 and it will take an estimated three or four shafts to recoup the investment, says Master Drilling CFO Andre van Deventer.
Master Drilling has ring-fenced its exposure of R60m to the project, protecting the company if there is any setback. The Industrial Development Corporation funding the balance subject to phased targets being met.
Considering it costs R1m a metre to sink a shaft the conventional way, sinking at either that rate or up to 2m to 3m a day, Master Drilling hopes that its ability to sink nearly 1m an hour, will prove far more attractive to companies building new underground mines, says Pretorius.
Would you like to comment on this article?
Sign up (it's quick and free) or sign in now.
Please read our Comment Policy before commenting.