The main sink on the ventilation shaft commenced at the end of May, while collar construction on the main shaft is on target for actual sinking to begin in August 2007. It is believed to be the biggest vertical shaft system in the Anglo Platinum group in more than a decade.

Murray & Roberts Cementation is the shaft-sinking contractor on the project, while Murray & Roberts Construction has been sub-contracted for all the surface civils associated with the new mine. Both companies began work on the project in August last year, with construction scheduled to take about a year, and shaftsinking about three years.

The PK2 project comprises a downcast vertical main shaft for personnel and material, together with an adjacent matching vertical upcast ventilation shaft. The main shaft will be 8.7m in diameter and sunk to 1 180m below surface (33 Level), while the ventilation shaft will be 6.5m in diameter and will be sunk to 1 034m below surface (31 Level).

Snap Lake

Snap Lake plant prior
to stripping and
shipping to Montreal

The main shaft will access the declines from Paardekraal 1 Shaft on 28, 32 and 33 Levels, and the ventilation shaft on 29 and 31 Levels. The main shaft will be equipped with a steel A-frame headgear and a personnel / material winder, as well as a service / emergency winder. Surface civils encompass a standard shaft bank layout, a dedicated refrigeration plant, offices and change houses, together with bulk services such as water and electricity. They also include foundations for the winders and the winder houses.

Murray & Roberts Construction contracts manager Arie Nijhuis says that 25 000 m3 of backfill has been completed to date in order to finish the terrace around the main shaft. About 510 tons of reinforcing has been placed with an estimated 6 000 m3 of concrete to cast.

MAJOR INNOVATION
Murray & Roberts Cementation senior master sinker Johan Groenewald explains that while conventional shaft sinking will be done, a major innovation on the PK2 project is the use of a new electro-hydraulic drill rig.

“This is not new in the mining industry in general, but its application in vertical shaft sinking is new,” he explains. The drill rig was designed in conjunction with Anglo Platinum and Anglo American Technical Services, and built in Rustenburg. The new drill rig allows both floor and sidewalls to be drilled simultaneously. The two drill rig units to be used on the ventilation shaft are equipped with three booms each, as is the one being used for the main shaft.

A main consideration for applying this technology to shaftsinking is safety, as the new drill rig limits the number of people at the bottom of the shaft during drilling operations to six, as opposed to 16 with traditional rigs.

Commenting on the challenges associated with the civils portion of the contract, Nijhuis says these included the strict timeframe, as well as the logistical complexity of the site establishment.