Engineering & Mining Journal

AUG 2017

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MINE DEVELOPMENT AUGUST 2017 • E&MJ 33 www.e-mj.com that material is being drawn from the correct locations. "The goal is to get the best monitoring data possible," Steffen said, "And ideally the beacon would be installed in a high density in the cave." The beacons are usually installed into drill holes. "To come up with a Beacon in- stallation program, an iterative approach using the system's analysis software is common." This allows the installation to be optimized for performance and cost. When envisioning an installation, the miner should first determine the primary areas of interest in the cave. "Geological domains and their rock mass properties determine cave-ability," he said. "Expect- ed fragmentation and cave propagation in conjunction with the mine plan will drive this point." Next, use of existing drill holes and the cost of additional drilling should be considered. "The availability of drilling locations will determine the lengths of the required holes and if it is technical- ly viable to drill into the volumes of in- terest," Steffen said. "The hole lengths will define the drilling costs." Ultimately, costs can determine how many and where the beacons are located. When a basic plan is hatched, Elexon calculates the predesign feasibility, Stef- fen said. "To assess installation design, we perform sensitivity simulations based on proposed installation designs," he said. "If available, we include numerical modeling results provided by packages such as Itasca's Rebop." Once installed, the beacons move with the caved rock. Range measurements from the detectors are combined on a reg- ular basis to calculate a beacon's position in three dimensions and its movement over time. To survive the trip, the beacons, which are comprised of batteries, electronics, magnet and motor assembly, are encased in a shell designed to withstand immense pressure. The shell can withstand forces such as localized pressure from "tons of rock leaning onto it, impact forces from dropping from the cave back through an airgap onto the muck pile and fluid pressure of a head pressure of more than 1,000 m encountered during grouting," Steffen said. "The Beacon has internal features that protect batteries, electron- ics and spinning magnets from impacts." The detectors also can withstand high flu- id pressure, he said. Beacons get extracted through the drawpoints by LHDs, Steffen said. "The LHD then dumps them with the ore." Working in conjunction with Elexon's Networked Smart Marker System, Cave Tracker can paint a picture of anomalies in muck that could pose safety threats, such as air gaps. The markers, which are like wireless TDRs, detect movement in the range of centimeters, whereas Cave Tracker detects it in the range of meters, Steffen said. An advantage of the Net- worked Smart Markers and the beacons is they require no cables that can be snapped by hole displacements. "Net- worked Smart Markers measure the prop- agation of the seismogenic zone and the cave back while Cave Tracker will detect mass movement," he said. "Combining the data can be used to indicate the pres- ence of an air gap." Knowing the location and size of an air gap empowers the miner to manage it. Meanwhile, real-time data on cave propagation will empower miners to plan with exactitude, improve process con- trols and thus reduce dilution, Steffen said. "Efficiency gains are to be expected through better control over cave growth, through delayed waste entries and im- proved ramping up of production," he said. "For future caves, extraction, un- dercut layouts, and block heights can be optimized for better recovery and lower development cost." Exact planning, better processes, lower development costs and optimized ore recovery will significantly offset the drilling costs that accompany deploying the system, Steffen said. "The financial benefits through higher recovery, lower dilution and better predictability of mine performance would be in the hundreds of millions of dollars for a mid- to large- scale project," he said. "Compare that to an investment into drilling monitoring holes and installing Cave Tracker equip- ment, for which the costs would be lower than or around $10 million for a large- scale installation." Elexon is currently researching other mining applications for magnetic bea- con-based systems, he said. Inventory Tracking and Draw Cards Last June, Glencore announced the de- ployment of Modular's DISPATCH Under- ground 2015 Fleet Management System (FMS) to its George Fisher zinc mine in North Queensland, Australia. There the system is being rolled out to help man- Glencore's George Fisher mine will reportedly roll out DISPATCH 2015 Underground over an extended project period, the miner reported last year. Above, new pipeline installation at the mine. (Photo: Glencore)

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