Mechanical engineer Rod Pickering spent 20 years at the Chamber of Mines Research Organisation (Comro) running the stoping technology laboratory, the part of the now-defunct Comro that focused on hard rock, narrow-reef mining.

After leaving Comro in 1996, he spent another 18 years running his own business and again focused on the adoption of better mining methods in that narrow-reef space.

Now, as chairperson of the Centre for Mechanised Mining’s steering committee, Pickering’s message is crystal clear: South Africa’s narrow-reef mining has to move the next level, or the country will end up with closed mines on its hands.

The function of the ten-year-old Centre for Mechanised Mining Systems, located at the University of the Witwatersrand, is to identify appropriate technology applications, understand the people factors and adopt a systems approach to mining mechanisation and automation in some of the country’s deepest, darkest and most dangerous precious metals operations.

The latest breakthrough is a combination of mechanised equipment and selected blast mining (SBM), which provides the best of both worlds.

Pickering’s comments dovetail with those of veteran research commentator Dr R E (Robbie) Robinson, who has called for the introduction of SBM in South Africa’s narrow-reef stopes as a way of boosting the struggling sector. (Also see Two-Minute Interview on page opposite).

The mechanisation introduces efficiency and eliminates the needs for people in the vulnerable areas and SBM eliminates dilution and boosts metal recovery.

Mechanised mining methods have gone on apace outside of the hard rock, narrow-reef scenario.

Opencast mining, room-and-pillar mining and block-cave mining have, the world over, all mechanised successfully, leaving South Africa’s generally tabular-orebodied mines with an urgent need for a higher productivity solution.

Gold has been a serious laggard because the deciding factor when it comes to room-and-pillar mining, which is what most practitioners have adopted, is the angle of the dip being not more more than 100 whereas it is a substantially steeper 230 in many West Wits and Carletonville gold mines.

In chrome and platinum mining, where the dip is generally not more than 100, 30-million tons a year are being mined using mechanised low-profile room-and-pillar mining method in narrow-reef orebodies.

Original equipment manufacturers (OEM) have come to the low-profile party and the number of pieces of equipment acquired by mining companies has justified the OEM investment into equipment designed for narrow stopes.

However, the shortage of artisans to maintain the equipment does present difficulties.

“We’ve had a shortage of those kinds of hands-on skills for many years,” Pickering tells Mining Weekly.

To overcome the shortage, companies like Sandvik have established major apprenticeship training programmes.

There is also a shortage of management with an understanding of this mechanised method of mining and most graduates are being skilled up to do conventional mining.

To remedy that, the Centre for Mechanised Mining at Wits University has put considerable effort into course development on trackless mechanised mining, rock cutting and materials handling, and the university itself now has an MSc Honours degree in mechanised mining.

The most recent course on trackless mechanised mining attracted 40 people, an indication that the industry is recognising the shortfall and that the university has something to offer.

The enrolment of particularly black students into mining has been substantial in recent years.

However, because of the lack of mining uptake by students in the 1980s and 1990s, there is a middle-management gap and a shortage of mentoring, which the centre is also addressing.

COMRO’S DEMISE

An opportunity to introduce mechanised mining far earlier was probably lost as a result of the closure of Comro.

Even AngloGold Ashanti’s extremely promising effort at raise boring the reef goes back to 1974.

“It’s invariably not about new technology but about technology which is available and which can be adapted,” Pickering adds.

The centre has a systems approach and deals with the introduction mechanisation and SBM holistically and comes up with answers that suit particular needs rather than a one-size-fits-all approach.

“You fix one thing and if you're not careful, you get unintended consequences and find a bunch of other issues coming out of it,” Pickering has found from long experience.

The centre is also engaging in research and a number of PhD and MSc students are registered through the centre to do things that will add value.

SELECTED BLAST MINING

Pickering is engaged in a project involving the mining of a 400 mm thick reef using mechanisation with SBM.

The waste material is being blasted into the back of the stope, where it is being used as backfill.

Long holes are being drilled into the footwall of the reef, waste material that SBM is blasting into the back of the stope is being used as backfill and the precious reef is being cleaned out with a small dozer, similar to those used in underground platinum mines.

Pickering reports that Dr Immo Bock has been deploying the rock-breaking system for many years, but without the benefit of mechanisation.

“He’s been doing it with hand drilling and he’s had a lot of success with it but we’re now taking it a step further and saying we want to do it as a fully mechanised process.

“So we develop two drifts on strike and then we do long-hole drilling between the two. We blast the waste material into the back area and the density of that fill is going to be more than two.

“So it’s going to be a very dense fill. We pop up the footwall and we’re getting the benefit of not pulverising the rock, not getting all the fines and not losing the gold,” Pickering explains.

Productivity is increased creating scope to pay fewer personnel higher pay.

“Hard-rock, narrow-reef mining has to change. We cannot continue the way we are at the moment. It’s absolutely unacceptable. We’re going to end up by having none of these conventional mines left because there is no way with the current wage demands, and I’m not being negative about them, that the economics can stack up,” Pickering warns.

The current method of blasting scatters the finely divided gold and platinum ore far and wide and lowers the rate of precious-metals recovery significantly.
SBM shock fractures the rock instead of losing significant amounts of it in high-energy explosions.

“It’s not as if we are going to pull some magic bunny out of a hat and suddenly say we can go in there and do laser rock cutting,” Pickering says, adding that long-hole drilling is a tried and tested technology and that modern blast initiation systems are impressive.

The solution lies in packaging known technologies in a manner that cuts costs and enhances safety.

Far improved tempos of production result and the days of being pleased to 6 m a day in a 30 m panel can be left in the dust of the new approach.
 

ANGLE OF DIP NO LONGER MATTERS
The driving of two development ends on strike and the use of SBM renders the angle of the dip of the reef irrelevant and known mechanisation technology used the world over in narrow-vein greenstone belts can be adapted to suit South African conditions.

The tall, slim narrow-vein machines and are redesigned as low, wide narrow-reef machines.

“Just think about narrow-vein gold mining, which takes place in greenstone belts the world over. There are probably more narrow-vein mines than any other and typically they put in development drives on the reef and do long-hole drilling between the two to enable rock to be broken and taken out.

“We’re really talking the same methodology but just applying it into a different environment. The functionality of the machine is the same.

“When the first low profile machine was put underground, it had the same wheel motors, power packs, boom, feed and drifter but we just packaged it differently,” Pickering recalls.
 

CONVENTIONAL TO MECHANISED
In the 1980s, the Randfontein Estates Gold Mine, under Hugh Scott-Russell, was converted from a conventional mine into a mechanised one.

While conventional mining involves off-reef footwall development ahead of on-reef development, paying on reef takes place from the outset with mechanised mining – and Scott-Russell proved that it does not have to wait for a new mine but can be introduced in existing mines.

“You can do it with an existing mine but you’ve got to have a plan and you must understand the orebody, the mining method and the metallurgy,” he says.

With the back blasting that SBM offers, low-profile 1.8 m drill rigs, load haul dumpers or dumpers suffice and ultra-low profile machines are unnecessary.

The fully remotely controlled Austrian-made cutting machines are 1.2 m high.
“With the kind of fibreoptic links and the Internet connectivity now available, you can operate the machine remotely from Austria.

“With SBM, you can tram narrow and mine wide because you are stuffing all the wide into the back area. You can actually have low profile equipment of 1.8 m operating and you can still mine a narrow orebody,” Pickering adds.

The drive for mechanisation is generic throughout commodities and has arisen on the back of the need for more safety and productivity than conventional mining can offer.

The thousands of people being sent underground everyday are now examining the risk-to-reward ratio more intensely and demanding the greater reward that machine-mediated productivity can provide.

Consulting engineers performing feasibility studies on new projects are recommending mechanisation wherever possible.
JOB SECURITY AND SKILLS

A common issue that is raised when discussing automation and mechanisation in industry is job losses for those who used to perform the job manually.

However, rather than people losing jobs, they will be upskilled and make higher wages more justifiable.
Working conditions will also be improved as machines are deployed do the ‘dirty work’.

“The growth of mechanised mining in Africa, in line with global trends, is creating many more job opportunities for artisans, who are needed to support equipment in the field.

President Jacob Zuma announced the provision of ten more Further Education and Training facilities and OEMs have set up many training courses
 

CAPITAL COSTS VS OPERATIONAL COSTS

While mechanisation is capital intensive, there is payback over time and greater power or fuel use is mitigated by greater efficiency and needs to take into account the power consumed by conventional mining inputs including compressed air for drills, lighting and ventilation.

Low-profile rigs can drill holes in far less time than people using hand-held drills.

When Sandvik’s AutoMine system was launched in 2000, it was said to hold significant cost and safety implications for large-scale underground mining.

Since then, AngloGold Ashanti has fast-tracked the development of reef-boring technology that bores the reef and extracts “all the gold, only the gold, all the time, safely”.

No gold is left behind because of the elimination of the need for pillars as a result of immediate backfilling.
In the absence of drilling and blasting, there is no seismic shake-up.
Pictures have shown a 30-m-long hole at a 27° dip taking out gold reef alone, which should put paid to mine call factor issues.

Steps are now advanced to get the process to operate 24 hours a day, 365 days a year.

The new technology opens up unmined shaft pillars and ultra-deep mining.

AngloGold Ashanti’s South African gold reserves will double with its introduction but if it is not introduced, labour levels will fall.

Rod Pickering talking to Mining Weekly.