Engineering contractors Murray & Roberts Cementation has been awarded a number of new shaft sinking projects in Southern Africa, as well as in the Democratic Republic of Congo (DRC).
A contract was also awarded to the company in December last year to deepen the vent shaft in a mine on the West Rand. “The ventilation shaft needed to be deepened to the same depth as that of the main vertical shaft on the mine. This project was challenging with regard to the complexity of working below an existing shaft and deepening it so that the vent shaft could be split into a hoisting shaft, as well as a ventilation shaft,” Murray & Roberts Cementation business development executive Allan Widlake told Mining Weekly.
Murray & Roberts Cementation will be deepening the West Rand mine shaft by using a number of techniques, including blind sinking with drilling and blasting, as well as by raiseboring and slyping of certain shaft sections.
Another ventilation shaft project, on a manganese mine in the Karoo, in the Western Cape, is an addition to a development project that is under way at the site. Widlake explains that this project, with its complex geology, required a highly mechanised approach using a combination of methods.
“The area that we need to work in, is covered by about 100m of clay, so this presents a unique challenge in that there are not many options available to us to get through the clay. What we will do, is excavate the area by digging and, within hours, line the shaft to contain the clay before it moves back into place,” he says.
International shaft sinking
Meanwhile, in the DRC, Murray & Roberts Cementation was awarded a project to build a shaft for the sole purpose of dewatering below the openpit. This shaft is neither a hoisting nor a men-and-materials shaft.
Murray & Roberts Cementation has already begun mobilising for the DRC project, which is now in its first phase, known as the presink, when the shaft is sunk to a sufficient depth to enable access by the main sinking equipment for the main phase, or main sink.
Currently, the shaft is at a depth of 30m and will go down to a total of 90m where the project will then be converted from the presink phase, expected to be completed by 1 May 2010, to the main sink phase.
Widlake reports that, since the beginning of the contract, which began in about mid-December last year, there have been no major challenges despite the weather. He says that the rainy season has proved somewhat difficult to contend with but the project has been running smoothly until now.
Another international project on which Murray & Robert Cementation is working is the deepening of an existing shaft system that is expected to be completed in about August 2010. The shaft was raisebored to its full depth and progress is being made to equip it and all the immediate infrastructure with conveyor belts and load-out stations for conversion to a hoisting and a men-and-materials shaft.
Widlake says that each project is looked at individually and Murray & Roberts Cementation has engineered a unique solution to suit the individual requirements and all the challenges. The company has taken a number of factors into consideration that include time, cost and safety.