Engineering & Mining Journal

MAY 2019

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Page 47 of 83

UNDERGROUND MINING 46 E&MJ • MAY 2019 Nothing goes according to plan in min- ing, Rennie joked. "We didn't account for it during the installation and they didn't realize they had a problem until after the first blast," Rennie said. "With the slusher and the work platform, it's not a problem as they have a different arrangement. We had to do a bit of re- work. There are a few other minor im- provements we could make, but all-in- all, the initial trials look good." Using a slusher and set of conveyors on a steep grade, the blast will have to generate muck with a consistent level of good fragmentation. The consisten- cy of the initial blasts was reportedly the same as one would expect from a conventional blast. The system drilled the same pattern, which was loaded the same way and yielded the same results. The monorail advances on develop- ment and then its removed as they mine the stope. When the system is operat- ing, the operators could work from the platform. Typically, on development, the operators are working off the ground with remotes. They have an option to run on radio remote or manually. Energy is provided by rail-mounted power packs. Using two rubber-tired wheels on opposite sides of the monorail rail, these electrically powered drives advance the entire system on the mono- rail. "When they get on steep grades, they may need to use as many as two or three of these drive units," Rennie said. "We have designed battery-, electric- and diesel-powered versions." Slusher on a Stick The Muckahi loading system consists of a slusher pulling muck from the face to the apron of an elevated chain convey- or (the bridge conveyor), which places the material on the tail section of con- veyor. This mucking system is a "fancy slusher," Rennie said, explaining that it was a departure from the original de- sign that Stanford envisioned. Rennie recalled showing him the design for the "slusher on a stick," a term coined by Dawson Proudfoot, explaining to him that none of this was going to be easy on a minus 30° gradient. In this arrangement, the pulley that is typically mounted at the end of the muck pile is on an extendable boom that rides on the monorail. The boom extends the pulley out over the muck pile. While the slusher has the same back-and-forth motion, it's electrically powered rather than air powered. "We purposely kept the stroke very short, about 3-m maxi- mum," Rennie said. "It pulls the muck into the bridge conveyor, which has a 1.5-m apron that pivots with the boom. The boom arrangement forces the slush- er to drag the muck square with the apron. There is a tailpiece for the con- veyor, but no hopper." "When you run the numbers, the only way this system is productive is if the apron is kept in the muck pile and the slusher stroke is kept really short," Ren- nie said. "If it works as it should, it will be very productive." Time will tell. All the previously stat- ed savings figures are based on limit- ed development. Short, steep decline tunnels equate to limited development. This is new technology designed specifi- cally for steep development. Once Torex gets a handle on this system, they will be able to use it to pursue other diffi- cult-to-mine assets. A slusher pulls muck from the face to a bridge conveyor that loads a conveyor train. The boom arrangement forces the slusher to drag the muck square with the apron.

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