Murray & Roberts Cementation is pioneering new drilling technology at Anglo Platinum’s R2-billion PaardeKraal 2 (PK2) shaft near Rustenburg, which forms part of its Rustenburg Platinum Mines (RPM) operation.
The main sink on the ventilation shaft commenced end 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 2006, with the latter’s work on the project scheduled to take about a year, and the former’s 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 8.7 metre in diameter and sunk to 1,180 metres below surface (33 Level), while the ventilation shaft will be 6.5 metre in diameter and will be sunk to 1 034 metre below surface (31 Level). 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. It also includes foundations for the winders and the winder houses themselves.
Arie Nijhuis, Murray & Roberts Construction contracts manager, 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 000m³ of concrete to cast.
Johan Groenewald, Murray & Roberts Cementation senior master sinker, 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.” 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 does the one being used for the main shaft.
“A main consideration for applying this technology to shaft sinking 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,” Du Plessis says.
Commenting on the challenges associated with the civils portion of the contract, Nijhuis says these encompassed the strict timeframe together with the logistical complexity of the site establishment.