Murray & Roberts Cementation has secured two contracts at BCL Limited’s Selebi North Shaft in Botswana. Both contracts are related to the deepening of the existing shaft to access the ore body at a deeper elevation. Murray & Roberts Cementation is responsible for the planning, logistics, construction and quality assurance of these 14 month contracts.
“Currently, access to the ore body is via a vertical shaft and vehicle ramp system. Over the next two years the vehicle ramp system will reach a depth below the existing ore handling system where the present mining methods will become uneconomical. For BCL to sustain its ore production profile it has become necessary to deepen the existing vertical shaft,” Piet Esterhuizen, senior projects engineer at Murray & Roberts Cementation, says.
The first contract, which commenced in May 2009, is for the raiseboring of the 4.1 metre diameter shaft from 433 metres to 758 metres over a vertical distance of 325 metres to deepen the shaft. “Raiseboring was considered a more cost effective and safer option as opposed to traditional shaft sinking methods. It also allows for far greater accuracy especially with our Rotary Vertical Drilling System (RVDS),” Pat Muller, senior projects manager responsible for this raiseboring contract at Murray & Roberts Cementation, says.
The RVDS steering device will be used on the raiseboring project to ensure optimum accuracy. Pioneered by the company, the RVDS has been used on numerous contracts and the company has a comprehensive reference base.
“Essentially, this system is used to ensure accuracy on the drilling of the pilot hole and accuracies of between 0.005 and 0.15% have been achieved on contracts both in South Africa and internationally,” Muller says.
The second contract entails equipping the raisebored shaft and constructing the balance of the infrastructure, including all associated underground infrastructure such as the crushing plant, conveyors and loading facilities and loading bins as well as station equipping.
“Both projects will support the local industry and in particular the Selebi Pikwe industry as far as civil construction, steelwork fabrication and structural assembly and electrical installation is concerned,” Esterhuizen says.