MINING than three years , and we have been running a block cave for 15 years after all . Reconfiguring and repricing the tunnelling work has taken out hundreds of million ’ s of Rand ,” he says , and the move has been justified since the local contractor has added 2.5 kilometres to the tunnels and has reached the access point to the undercut , from which the ore will flow .
The focus now is on ventilation . To connect the Lift I and Lift II ventilation systems PMC has sunk two 450-metre shafts , 4.5 metres in diameter . The contractor , Murray & Roberts will then connect the undercut and production levels with a number of raisebores . That ’ s going smoothly , however the twin ventilation shafts being sunk from the surface present a real challenge . The contractor Master Drilling is once again approaching the limits of mining capability : the company designed and built the RD8 raiseboring machine specifically for the PMC project , which entails the construction of two 6.1-m-diameter ventilation shafts , each with a recordbreaking depth of 1.2 kilometres . The RD8 machine operates faster and is significantly cheaper than the conventional blind-sinking technologies , and requires only two operators per shift . But raiseboring has never been tried at this depth and diameter in combination . “ The driver for us is that we were looking to maximise the vent requirement without doing multiple holes : the bigger you go the lower the cost is a theme running throughout the project . We need to stay in the cost envelope and engineer accordingly .”
The traditional approach to project management is that the owner ’ s team oversees the EPCM and the EPCM oversees the contractors . On Lift II it made sense to leverage the expertise of the people who had been involved in Lift I construction – after all they are very similar in design . Accordingly , Fouché and his team have worked out a more integrated management approach with the
www . palabora . com 69