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Shotcrete for primary support adds to safety

September 1, 2009
by Norm Tollinsky
In: News with 0 Comments

Xstrata Nickel opted for a path less travelled in deciding on a development methodology for its Nickel Rim South Mine. Rather than stick with the tried and true practice of using screen and bolts for ground support, the project team chose to standardize on shotcrete for primary support.

“We executed lateral development using shotcrete as primary support for the Mine D project at Kidd Creek (in Timmins) and it worked very well from a safety perspective,” said Nickel Rim South construction manager Hugh MacIsaac. “It took the worker away from the face during the ground support part of the cycle and gave us good results.”A search for best practices during the set-up and shaft sinking phase of the project took MacIsaac and his team to mines in Scandinavia and Australia that were successfully using shotcrete for primary support. Among the most impressive sites was Newcrest Mining Limited’s Cadia Hill Mine in New South Wales, where development crews were achieving eight metres per day in a single heading with an Atlas Copco Rocket Boomer L2C jumbo.

L2C jumbos

Nickel Rim South eventually purchased five L2Cs and, together with its lateral development partner, Cementation Canada, set a target of 5.4 metres per day for a single heading and 7.6 metres in multiple headings.

Manpower shortages during the height of the commodity boom prevented the Cementation crews from achieving the targeted rates of advance, but the job got done.

“The plan was to have 80 per cent trained people and 20 per cent new people, but I think we ended up with 20 per cent experienced people and 80 per cent without much experience, so that was a challenge,” said MacIsaac. “We worked our way through it and got the development we planned for the first phase of the project. We delivered 10,000 metres of lateral development by December 2008, along with 86 kilometres of diamond drilling.”

A plan to replace Cementation crews with Xstrata miners was accelerated when the company decided to cease operations at its Craig and Thayer Lindsley mines and subsequently placed the Fraser Mine on care and maintenance.

“The method we chose, I think, is the right method. It has a lot of upside, but the challenge is changing people’s behaviour,” said MacIsaac. “I don’t care if it’s going from a mucker machine to a scoop tram, from a long tom to a jumbo, or a jackleg to a long tom. Making change is tough.”

By November-December, Xstrata crews were getting close to their target of five metres per day. This summer the goalposts get moved out to six metres based on the commissioning of ancillary infrastructure such as shotcrete receiving systems and ore and waste handling systems.

Xstrata purchased seven, eight-yard Caterpillar 1700 load-haul-dump machines, two Cat 2900 loaders, a couple 45-tonne Cat trucks and three IT loaders for its Nickel Rim South development fleet.

Marcotte

The utility fleet was supplied by Sudbury-based Marcotte Mining Machinery Service Inc. It included three wet shotcrete sprayers, scissor trucks, fuel trucks, boom trucks and transmixers. Nickel Rim South chose to go with the Marcotte utility vehicles because of the efficiencies they offered.

“We wanted to minimize the amount of spares,” said MacIsaac. “They are all mounted on the same carrier and have the same axle and the same drive, so if you’re trained to operate one, you could operate any of them. Maintenance is also easier. We paid a few extra dollars to get the commonality, but it was worth it.”

A special effort was made to design the roadways for maximum productivity. A plus three or minus three grade keeps the water off the roads and ditches along the five metre wide drifts provide drainage.

Temporary maintenance shops with overhead cranes on each of the three development levels will be used until 2012, by which time a ramp system will be completed and one permanent garage is able to serve machinery on all three levels.

The scope of work this year calls for 11.5 kilometres of lateral development and approximately 546,000 tonnes of ore production.

MacIsaac is especially proud of Nickel Rim South’s safety record, achieved in part, he says, because of the use of shotcrete as primary support.

“Five years without a lost time accident is something we’re pretty proud of. Having gone through all of the challenges with regard to the marketplace in the last couple of years and to still be on schedule and on budget with a stellar safety record is pretty impressive.”

 

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