Modern Mining January 2018

DIAMONDS

emulsions being used – a more efficient way of charging holes than the stick-type explo- sives previously employed. For the VUP, the explosives are being supplied by AEL Mining Services. Kühn says that the primary reason for using the Canadian-shaft-sinking system for the VUP is its inherent safety. “It eliminates all concur- rent activities, so you never have a situation where one team is working above another,” he explains. “Moreover, there are far fewer people required compared to conventional sinking. Typically, we have between seven and nine people working in each shaft at any one time, which is probably about a quarter the number you would need using traditional methods. We are very impressed by the system. It is clearly the correct strategy and we can see the results – for example, in the main production shaft, we have now worked for more than 500 days without an LTI.” While the Canadian method may be safer, it is not necessarily faster and Kühn acknowl- edges that the average daily rate of advance of about 1,5 m is somewhat slower than expected. “In practice, this has not been a problem and we’ve been able to work around it,” he says. Turning to the 6 x 5 m decline system, Kühn reports that progress has been excellent. “In 2016, we achieved a 55 % improvement in development rates and this year we’ve recorded another 15 to 20 % increase. We’ve built up real momentum and in October 2017 we achieved close to 175 m of development, which is a record. We have a single crew on site but with lateral development now underway we are mobilising a second crew, with a third crew to follow in March this year. Ultimately, we will

peak at six capital development crews.” The primary mining fleet deployed for the decline comprises Sandvik machines. Two Sandvik DD421 twin boom electro-hydraulic jumbos are used for drilling the face and for rock support and work in conjunction with Sandvik LH514 LHDs and Sandvik 40-t capac- ity underground haul trucks. All the equipment is owned by De Beers but operated and main- tained by Murray & Roberts Cementation. In all (and including the vertical shafts), Venetia Underground requires 50 km of devel- opment (and 234 km over the life of mine). Currently, just over 5 km have been completed. The fact that the VUP will start delivering ore in 2021 is a feather in the cap of the VUP team. As Nortje points out, this is over a year earlier than originally anticipated. “As initially planned, there was very little overlap between

Inside the 6 x 5 m decline.

“Typically, we have between seven and nine people working in each shaft at any one time ... .”

Schematic of Venetia Under- ground Project.

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