Modern Mining June 2018

COVER STORY

vent shaft while a Redbore 90EX has been used to raise drill a nearly 2 000-m deep, 6,1-m dia­ meter vertical shaft in four approximately 500-m lifts for the Mindola Deeps Expansion Project. “To the best of our knowledge, this latter project represents a world record – in terms of depth – for a raise-bored shaft,” states Schultz. Like all of its peers, Redpath places a huge emphasis on safety and recently recorded four years of LTI-free operation on the Synclinorium project (from start to project completion). In South Africa, Redpath recently completed a raiseboring project at Sasol’s Impumelelo coal mine. The scope of the work entailed the piloting and reaming of two 186-m deep, 7,3-m diameter ventilation shafts, includ- ing the lining of both shafts by means of a Remote Shaft Liner. The machine used was the Redbore 90EX. The 7,3-m diameter holes set the African record for the largest diameter raisebore holes reamed to date. While Redpath Mining Inc has completed many vertical shafts around the globe, Redpath Mining Africa has had limited opportunities to complete a deep-level shaft in the Africa region using conventional shaft-sinking meth- ods. Schultz says that this in part reflects the fact that shafts of this type are few and far between. “We do, however, have a full deep- level shaft capability,” he states. “In South Africa we’ve sunk sections of vertical shafts

South Africa and the Zambian Copperbelt. The Redbore raise drill machines are man- ufactured by Redpath in North Bay, Canada (the first unit was designed and built in 1987) and range from the Redbore 30 (a blind borer), which can drill raises up to 1 m diameter to a length of around 50 m, to the giant Redbore 100, which can handle diameters of up to 8 m to a depth of more than 1 000 m. The current fleet comprises a mixture of electrically driven vari- able speed and hydraulic drives. More than 70 Redbore machines have been built to date and have collectively reamed raises totalling approximately 318 km. A machine which will become a key part of Redpath Mining Africa’s raiseboring offering is the new Redbore 65, which is capable of drill- ing up to 3,5 m diameter over a raise length of 300 m. The machine – now at an advanced pro- totype stage – will be able to fit into a 4,5-m high excavation and will be compatible with the Redtrax raise drill transporter, a purpose- built, low profile unit designed specifically for the independent and swift underground trans- port of Redbore raise drills between sites, which eliminates dependence on client resources such as telehandlers, forklifts and LHDs. The Redbore raise drill machines have dis- tinguished themselves on Redpath’s Zambian Copperbelt contracts, all for Mopani Copper Mines (MCM). A Redbore 100 has been deployed on the 6,1-m diameter Synclinorium

A twin-boom drill jumbo working on the Synclinorium contract.

20  MODERN MINING  June 2018