Far from the Dickensian horrors of ‘the widow maker’ a new breed of remote controlled, real-time underground mining machines is being developed with an eye to a wide range of workplace and cost-saving benefits. Michael Sheffield writes for Australian Mining.
One of mining’s many constants is the imperative that exists to shift dirt and rock quickly enough to reach the targeted ore body before the development capital runs out and then to mine the reserves that have been created quickly enough to meet contractual obligations.
That imperative shaped the move to mechanised rock drilling in the 1870s.
One of the mining’s tragedies is the price in human suffering that has at times been paid for the benefits of new technologies. Conversely, securing mechanisms which ensure the effective mitigation of risks associated with any productivity improvement initiative before it can be implemented is one of its triumphs.
The high human cost of mechanised rock drilling is seen graphically through Geoffrey Blainey’s eyes.
“The slow advent of the mechanised rock drill from the 1870s had intensified the fine dust in Mines. Its drilling speed created far more dust than the old hand drills that were hammered into the rock with the slow blows of a miner’s hammer. One American rock drill was aptly named ‘the widow maker’. The increasing depth of mines made ventilation difficult, and often no current of air blew away the dust from the dead ends where men worked. The practice of employing three shifts of miners, a practice not so common in the smaller mines of earlier years, gave the dust only Sunday in which to rest and settle. In quartz mines the fine particles of silica slowly damaged men’s lungs and bronchial tubes.” (from ‘The Rush That Never Ended’).
This exposed the men to the nineteenth century’s great killer, tuberculosis: “The tubercule germ spread rapidly in the quartz mines, for many men in the first stages of the miner’s disease passed on the germs by spitting or by shouting close to their mate’s face in order to be heard above the roar of the rock drill”.
More than a generation passed before the disease and the means by which it could be prevented were understood. “Ironically,” as Blainey notes, “once the menace was seen it could easily be cured by playing water on the dust and by ventilating the deeper workings. However, many miners ignored their water jet and many companies owning deep shafts on narrow leases recoiled at the expense of providing ventilation”.
Small companies unable to extend their drives went down, often to extraordinary depths. The Magdala mine at Stawell reached 2,400 feet in 1880. Bendigo’s North Old Chum mine, on two acres, went down 2,300 feet, with almost two miles of connections, at that depth, to other shafts on the Old Chum Line.
The situation was hazardous. Tragedy was inevitable.
“When the Bendigo field collapsed during World War I it had at least 53 shafts that were over 2,000 feet in depth and one shaft almost a mile deep. Skyscrapers reversed, they dwarfed the rising Manhattan skyline,” Blainey says.
Southern Lights at Broken Hill
Broken Hill in the last decades of the nineteenth century presented its own challenges.
When BHP stopped mining at Broken Hill in 1939, the seven leases that Charles Rasp and George McCulloch had pegged out along almost two miles of the load line in 1883 had yielded 189 million ounces of silver, 1.45 million tons of lead and 620,000 tonnes of zinc worth a combined £54,000,000.
But while these leases were immensely rich they presented challenges that the company’s directors felt Australian mining engineers could not meet.
More than four miles long, 500 feet wide and up to 2,000 feet in its vertical thickness, the line of load was arranged in up to six ‘lenses’ or ‘margins’, hanging below the oxidised ironstone cap in furled curtains that mirrored the Aurora Borealis.
“The directors of BHP had the foresight to look abroad for the best mining engineer that money could buy, and William Patton, from Navada’s famous Comstock Lode, came and introduced square-set mining to Australia. Heavy sawn Oregon beams were set in stopes in much the same way that modern buildings use steel girders,” geographer, Ian Coghill said, in his telling of the story in ‘Australia’s Mineral Wealth’ in 1971.
It was a costly solution but for a mine that had already produced more than seven million ounces of silver and 28,000 tons of lead, the wastage associated with a cheaper solution could not be justified.
The attendant risk, of course, was fire and serious fires burned at Broken Hill in 1895, 1897, 1906 and 1923.
From Fire to Floods
For gold miners tracing out buried rivers of alluvial gold deep underground, the fear was not fire but the real and present threat of flood.
Twenty-two minors perished in floods in the New Australian Company’s mine at Creswick in 1882 when, as the result of a measurement error by the mine’s engineer, the drives that they were extending from a new shaft broke through into the mine’s old abandoned (and flooded) workings that were 55 feet closer than they understood them to be.
Modern industry standards limit the possibility of such tragedies happening today but even with its safety standards, mining remains a hazardous occupation. The imperative to pursue ore bodies located deep below the surface remains and will continue into the future as Australian mining companies move to extend their known mineral reserves.
Far removed from the world of ‘the widow maker’, today’s intelligent drill rigs incorporate CAN-bus based operating systems and are designed for blast hole drilling, drifting and tunnelling.
Their computer platforms support a comprehensive range of applications which allow for the design of drill plans, laser lines and tunnel lines.
Boom positioning and the drilling of pre-selected drill plans can be fully automated, semi-automated or manual directed.
In-built trouble shooting systems simplify fault diagnosis and minimise down time. Tramming speeds of up to 15km/h and up to 6km/h on 1:8 inclines give quick, efficient manoeuvrability, and mine workers can operate them effectively for extended periods of time from air-conditioned and ergonomically designed cabins.
Non-entry technology enters the ring
But beyond this ‘boys’ toys’ world, research is being undertaken which will allow hard-rock mining to be carried out efficiently by smart machines controlled from outside areas of elevated risk.
The development of this transformational non-entry mining technology is a major initiative of CSIRO’s Minerals Down Under research program.
By making it possible for mining staff to perform operational tasks tele-remotely from outside areas of elevated risk, CSIRO’s ROES® mining system will help mines of the future operate more efficiently by equipping them to access resources that are currently ‘stranded’ due to geological or other constraints.
By providing a safer and more economic way of mining orebodies by drill and blast rock fragmentation within a stope, it is hoped that this system will significantly reduce the time and cost required to bring ore on-line and shift marginal mineralised zones from resource to reserve.
The ROES® method deploys unmanned, remote-controlled machines from a shaft positioned either within or close to an orebody to drill, blast and recover ore. Drilling and blasting are performed using automated platforms that are lowered and raised in the shaft. Rock is extracted from the base of the stopes from conventional drawpoints.
Operators use on-line software to design blasting patterns, asses mining conditions, and monitor product quality.
The use of remote-controlled real-time survey options means that blasting patterns and stope shape can be modified easily during the production cycle, if required.
Vertical or inclined access to the orebody (rather than lateral access) facilitates reductions in development metres required which are expected to lower production costs by an estimated 15-20 per cent.
The ROES® system, now being developed in collaboration with Orica, and with strong interest from major mining companies, incorporates recent advances in communications, remote and automated equipment control, sensing, and machine guidance technologies proven in other projects undertaken by CSIRO and Orica.
“ROES® is important commercially because it has the potential to reduce underground mining costs sufficiently to bring on-stream a large amount of resource that is currently sub-economic and located around existing orebodies.
“These resources may be deeper or they may by located in ‘pods’ to the side of an existing mine, but they are of interest because they constitute a resource that is reasonably known and are often close to existing mines and processing infrastructure,” said Jock Cunningham, Theme Leader, Transforming the Future Mine Minerals Down Under National Research Flagship, CSIRO.