Master Drilling to use new tunnelling method at Petra mine
JSE-listed Master Drilling has been given the go-ahead by Petra Diamonds to use an innovative method at its new Cullinan mine to develop tunnels at twice the speed of traditional blasting methods. Fochville-based Master Drilling is using its vertical raise-bore drilling system in a horizontal application at the block-cave Cullinan mine, where the kimberlite is an ancient carrot-shaped pipe of volcanic material bearing diamonds. The method of extracting this pipe is to construct a tunnel ringing the kimberlite and then punch tunnels across the pipe in a grid pattern to collapse the kimberlite above the tunnel into draw points to be carried away and hauled to the surface. The development of the grid tunnels is what this technology tackles and Master Drilling CE Danie Pretorius said the doubling or tripling of advance rates from 2m per day with drilling-and-blasting methods to 4m or 6m a day with the horizontal raise bore system would bring benefits to companies that could deploy the s...
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