Modern Mining January 2016

COPPER

SA’s grand copper heritage

about 18 m below, which receives the frag- mented rock through the drawbells; and  the ventilation level, 25 m below the produc- tion level. While Palabora’s carbonatite rock mass has the advantage of well-delineated ore, it is also considerably harder than the kind of rock nor- mally mined by the block-cave method – in the kimberlite of diamond mines, for instance. “We pioneered some ground-breaking tech- nology during the Lift I phase, as this was the

‘early works’ – the vital development of a twin decline and supporting engineering infrastruc- ture from Lift I down to the new orebody. “This was a significant investment by share- holders, showing the confidence they had in the project, even in the early stages,” said Fouche. Conducted as a close collaboration between the mine and contractor Byrnecut South Africa, the twin declines of 3,6 km each preceded apace, achieving rates of advance of 10,5 m per day; the process also allowed for an upgrade

Above: The open pit at Palabora. Note the subsidence of the pit’s north-west wall.

Below: Layout of the Palabora mine showing the open pit and Lifts I and II.

of electrical infrastructure, services and ventilation. One decline will be for services, while the other will house the switchback rock conveyor carrying ore to the base of the verti- cal shaft at Lift I level. A temporary crusher is to be installed at the base of the conveyor to be used for development tonnages and first pro- duction; at the other end, ore will be lifted to surface in the shaft. The Lift II mining footprint is now being developed from the twin decline, with access drives based on the classic herring-bone block-cave design used in Lift I. Three levels will be developed, linked to each other by connecting ramps:  the undercut level is where the orebody is drilled and blasted so that it ‘caves’ into the drawbells;  the extraction or production level

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January 2016  MODERN MINING  63