Modern Mining September 2018

SHAFT SINKING AND RAISEBORING

of workers required being about a third less than would be needed in a conventional sink.” Widlake says that Murray & Roberts Cementation will use the method – or a hybrid of it – for all future shaft-sinking projects. “There are aspects of the system that we believe can be improved – particularly with respect to the mucking process – but overall we’re satis- fied that it is the right way to go. Certainly we will never return to the traditional method.” He adds that the company has been particularly impressed by the sling-down drill rigs which have proved far superior to anything it has used before. “The next step will be to go to full hydraulics with them,” he says. While Murray & Roberts Cementation is almost certainly the African leader (and possi- bly the world leader) in terms of the number of conventionally sunk shafts it has executed, the company is also a major player when it comes to raiseboring (or raisedrilling, as it is also known), with projects having been completed all over Africa. “Raiseboring is a key component of our business,” states Widlake. “We source most of our machines in house from our Australian company. We are able to match all our com- petitors with respect to drilling depth and diameter of holes and we’re constantly work- ing on improving the technology. For example, we’re collaborating with an Original Equipment Manufacturer (OEM) on a shaft-enlarging machine – an updated version of the V-mole – which will allow us to enlarge raisebored holes to 9,5 m in diameter. We’re also working with

portal crane required will be sourced here in South Africa.” The use of the gantry system is not the only major innovation at Venetia. As has been widely reported, Murray & Roberts Cementation is also deploying for the first time in Africa a new shaft-sinking methodology derived from its sister company, Cementation Canada, for the main sinks. The new system involves the use of ‘sling down’ vertical drill rigs (VDRs) and verti- cal shaft muckers (VSMs) accommodated in the sinking stage. A characteristic of the system is that all activities in the shaft-sinking cycle are in-line, with no two jobs taking place simulta- neously, which makes for enhanced safety over the traditional South African sinking method. With the shaft sinking advanced (with the production shaft having reached a depth of 910 m by the end of July this year and the service shaft 875 m), Murray & Roberts Cementation has now built up considerable experience with the Canadian system. Widlake says that it has met most of the com- pany’s expectations. “We adopted the system primarily for safety considerations and our experience thus far has confirmed that it does indeed deliver a superior safety performance,” he notes. “There have been no fatalities and the Lost Time Injury (LTI) record is excellent. The production shaft, for example, has now gone over 770 days without an LTI. We have not yet achieved the productivities that we believe the system is capable of but it is certainly not slower than conventional shaft sinking. It is also far less labour intensive with the number

Murray & Roberts Cementa- tion has been awarded a five-year contract to under- take the contract mining at the Kalagadi Manganese Mine (seen here) in the Northern Cape.

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38  MODERN MINING  September 2018