Engineering & Mining Journal

JUL 2013

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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SOUTH AFRICAN GOLD which can be kilometers away. Dixon noted that miners were spending up to 10 hours a day at work, but almost half of that was spent moving to and from their stations. "A miner works an eight-and a half hour shift, with a couple of hours overtime. He spends three or four hours walking. How is he supposed to increase productivity? Impossible," Dixon said. "It's not the work he is doing, it's the time he has to do it in." Some companies were looking at increasing shifts to 12-hours, but with temperatures at deep levels reaching 130°F it would be pushing human endurance to the extreme. Dixon was also skeptical that technology would lead to the large-scale replacement of humans underground. "We missed out on the mechanization era. Now people want to move directly into automation," he said. I am not sure this can be done." South African mines have lagged their international counterparts in research and development, leaving them at a disadvantage. While Australian and Canadian firms had invested around 5% of their turnover into new ideas, South African companies set aside almost nothing for this purpose. Instead, they relied on the belief that they had cheap labor at their disposal. "Labor never was cheap. Not if you take into account all those numbers—the cost of hostels and accommodation, nutrition, HIV-AIDS treatment. Cheap labor was an illusion," Dixon said. It's not that zero innovation has taken place. Companies over the years introduced—or tried to—a variety of ideas. These ranged from underground chair lifts to reduce traveling time to directional drilling, which has revolutionized the oil and gas industries. Even "solution mining"—turning gold bearing rock to sludge using acid—had been attempted. Many of these were now used to a greater or lesser degree, but none had provided the revolution needed to replace men in significant quantities, or overcome the challenges related to working at great depths. Reef-boring at Tau Tona A possible exception is Anglo Gold Ashanti, which recently said it was exploring technology it described as a "game changer." During a recent briefing, Srinivasan "Venkat" Venkatakrishnan, the incoming CEO, said a pilot project at the Tau Tona gold mine, currently the world's deepest, west of Johannesburg near the town of Carletonville, had provided impressive results. The new technology had saved time and reduced underground waste. "It could double the reserves of the company, from a South African point of view. It could potentially add another 30 million ounces," Venkat said. The technology is now being rolled out at other mines and the cost of its implementation would be in the order of $40 million over a three-year period. This, he added, "was not a lot of money." Drilling had been substantially speeded up, from 3 m/d, to a breakneck 20 m/d, Venkat said. Ultra high-strength backfill was being used to end the need for large pillars within tunnels. According to an Anglo Gold case study on the project, blasting—and the need to remove people from higher-risk areas—has been reduced, which facilitates continuous mining. Reverse-circulation technology is applied to geological drilling, to ensure accelerated geological information. Enhanced orebody information is a critical ingredient in transforming the mining method from its current labor-intensive process to a continuous mechanical method. In reef boring, the first prototype raisebore machine completed five test reef holes using a double pass technique, the company noted. Further tests using a second prototype raisebore machine have commenced, making use of a single-pass technique. The second prototype machine is more powerful, and has resulted in increased drilling rates by incorporating improved forward-and-backward thrust and rotation control. Substantial progress had also been made in the design and testing of ultra highstrength backfill. Surface tests established that it could be pumped over the required distances, and that it would achieve the backfill strength needed for the reef-boring application at Tau Tona. An underground batch plant was built in February. Sibanye's harvest production plan shows steady depletion through 2028. www.e-mj.com JULY 2013 • E&MJ; 41

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