Engineering & Mining Journal

NOV 2018

Engineering and Mining Journal - Whether the market is copper, gold, nickel, iron ore, lead/zinc, PGM, diamonds or other commodities, E&MJ takes the lead in projecting trends, following development and reporting on the most efficient operating pr

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Page 42 of 83

SLOPE STABILITY NOVEMBER 2018 • E&MJ 41 sions often being made on the basis of prior-event parameters and corporate or personal biases and preferences. How- ever, leaning too heavily on past expe- rience to predict future events can lead to problems, even when the data's good — particularly when independent critical review is absent. A case in point is the landslide that occurred in the pit of the Bingham Can- yon copper mine in April 2013, regarded as the largest man-made slide in North American history. Two separate slides that happened within a few hours of each oth- er unleashed an estimated 144 million tons of dirt and rock that tumbled 2,000 ft from a point high on the pit wall and spread along a runout distance of almost 10,000 ft, burying the pit floor under 66 million yd 3 of material and triggering a mild earthquake under the mine. The Manefay slide, as it is called, was a financial and operational calamity for the mine's owner, Rio Tinto, but from a geotechnical point of view, it could al- most be considered a qualified success in terms of how to go about monitoring a potential slide area. The geotechnical staff couldn't prevent the incident, but the mine's comprehensive monitoring program allowed them to become aware of the problem months before it hap- pened, keep close tabs on its progress, and recommend timely evacuation of per- sonnel from the pit well before the slope failure occurred. Even so, the overall size of the land- slide significantly exceeded pre-event estimates, and the slide itself was quite different from previous slope failures at the mine. Whereas most earlier slides were progressive in nature, with a grad- ually accelerating rate of movement culminating in a slide that would slow and stabilize over the course of a day or two, the Manefay incident was actual- ly a rock avalanche, forcefully spewing millions of tons of material from the pit wall, burying the pit bottom with a 600-ft-thick layer of dirt and rock that reached the far side of the pit floor, an area considered safe from the slide where part of the production fleet had been parked during evacuation. More than a dozen haul trucks and three shovels, along with bulldozers, drills and graders, were damaged or destroyed there, and a huge section of the pit's main haulage road was obliterated. Clearly, despite the existence of previ- ous slope failure records, deep profession- al experience and an extensive geotechni- cal monitoring setup — including slope stability radar units, along with extensom- eters, a prism network and microseismic equipment — the mine's geotechnical team was caught off guard by the scope and nature of the slide. What was over- looked, forgotten or disregarded? E&MJ spoke with Brad Ross, a professor of prac- tice and director of the nascent Geotech- nical Center of Excellence (GCE), Lowell Institute for Mineral Resources, at the University of Arizona. Ross managed the Bingham Canyon mine planning team be- fore and after the landslide occurred and has authored a book titled Rise to the Oc- At GIW our commitment to service is more than a promise, it's a resource you can count on to keep your equipment running. We offer service and repair support that extends the life of your rotating equipment—even if it's from another manufacturer. Count on GIW to provide personal assistance when and where you need it—either on the job site or at one of our service centers. Discover what your business can do when dedicated support revolves around you. Service and Repair That Revolve Around You GIW Industries, Inc. (A KSB Company) ·

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