Drilling down to the depths of the problem


Giant drill made in Fochville could reduce costs and danger

The technology focuses on a solution to sink hard rock shafts at between 7m and 11m in diameter up to 2,000m deep. It is foreseen that this will enable drastic reduction in costs and increased efficiency.

New home-grown technology might be the solution to the grim forecast by the CEOs of major gold and platinum mining companies that there will be no more deep-level shafts sunk in SA.

And the outlook might not be as bleak as Harmony Gold CEO Peter Steenkamp, Impala Platinum CEO Nico Muller and Anglo American Platinum CEO Chris Griffith painted it at the Joburg Indaba mining conference last week, with conceptual shaft-sinking technology possibly providing an alternative to existing shaft-sinking practices.

An unassuming company based in the small mining and farming town of Fochville to the west of Johannesburg, which is a major provider of drilling services to the resources industry around the world, is scrambling to find new technologies to access ore bodies faster, cheaper and safer, and with as few people as possible.

Considering a shaft of about 1.5km deep and with a 10m diameter would cost about R20bn to build over 15 years, with another decade or so to recover the capital, investors would wait for 25 years before they’d start seeing profits.

Master Drilling unveiled a concept at the Mining Indaba in Cape Town two years ago that entailed a giant boring machine that could sink a shaft with a spinning reamer and a flat disc with rock-grinding teeth — a system known as “blind boring”.

“SA’s mines are so deep that everything done at depths of 2km to 4km is complicated. So being able to sink shafts for a lower cost and faster will bring about the necessary change,” says Master Drilling director Koos Jordaan.

“The shaft-boring technology that Master Drilling is developing focuses on a solution to sink hard rock shafts at between 7m and 11m in diameter up to 2,000m deep. It is foreseen that this technology will enable drastic reduction in costs and increased efficiency,” he says.

The argument Master Drilling CEO Danie Pretorius makes is that there is enormous value generated in a mining project by deploying a machine that can sink a shaft a lot faster than the conventional and slower drilling and blasting technique using people working at the bottom of a very deep hole.

Instead of waiting decades for a return on investment, that timeline can be substantially reduced, pushing previously unviable projects over the investment decision hurdle, he says.

Implats is considering building a shallow, highly mechanised mine in the Waterberg and this is where this type of technology could come into play, says Implats corporate relations executive Johan Theron.

“Expect this technology to first find an application in projects such as this. Once it is proven at this scale and depth it can be considered for deeper shafts, but it’s still unlikely, in my view, to fundamentally change the investment outcome,” he says.

The reasons for Implats’ decision not to invest in more deep-level shafts — beyond the two that it is ramping up to full production — include the loss of shareholder appetite for multibillion-rand investments over a decade, the long wait for a return on investment, safety concerns, soaring labour and input costs, lower labour productivity at depth, lower extraction rates in deep mines and the largely inflexible methods used in conventional, labour-intensive operations.

“Conventional mining has traditionally been the lowest-cost production for many years, but because of all these factors it has now become the most expensive by some margin. And it is likely to become progressively more uncompetitive,” Theron says.

“In a world where you have no real opportunity to make a return, people will simply stop investing in these ventures. The best we can expect is for current investments to be mined out over time.”

Implats CEO Muller said at the conference it was “ludicrous” to think of building deep-level mines to compete against the host of shallow mines in production and under development in SA and Zimbabwe.

Master Drilling is testing an innovative mobile tunnel borer that can develop horizontal tunnels with inclines or declines of up to 12 degrees, with a diameter of 5,5m, ideal for shallow mines where decline tunnels are needed to access the ore body.

Jordaan is clear that “this isn’t a silver bullet for gold mines”. The machine isn’t currently designed to operate in the increased rock pressure and stresses at the depths at which South African gold mines operate.

However, the unique configuration of the mobile tunnel boring machine would allow companies to more quickly develop access tunnels to open ore bodies compared to drilling and blasting, which also introduces additional stress in the host rock.

Master Drilling is testing an innovative mobile tunnel-boring machine that can turn in a 30m radius and work on 12-degree inclines or declines, making it a cheap, fast, safe option to develop declines in underground mines.

This article provided by NewsEdge.