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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SLOPE STABILITY 42 E&MJ • NOVEMBER 2018 www.e-mj.com casion: Lessons From the Bingham Can- yon Manefay Slide, which provides insight into the events leading up to and in the af- termath of the slide as well as suggestions on how to manage more effectively during both normal operations and crises. The Manefay slide was a "black swan" event, according to Ross — something that is unexpected, has a major impact and is the first recorded instance of its kind. But, he noted, "A black swan event is only a black swan because no one considered the real possibility of the event occurring. If the way the Manefay failed is clas- sified as a black swan event, what critical control measures can be used to prevent or at least anticipate such events?" Ross recommended three measures that can help to identify and prepare for unique occurrences such as the Manefay slide. However, he cautioned, there's no guarantee that any particular measure could have predicted the scope and effect of that event. He suggested: • Using independent experts – Placing too much confidence on site-specific per- sonal experience and historical records can be risky. In the case of the Mane- fay slide, outside experts might have been able to expand awareness of dif- ferent slope failure modes, and prob- ably wouldn't be swayed one way or another by the mine geotechnical team's previous experiences and biases. • Challenging the basic assumptions of your staff – Commonly referred to as "wearing a black hat," this involves facil- itating frank, give-and-take discussions of the problem in a nonjudgmental environment. • Sharing what you've learned – Dissem- inating knowledge of the characteristics and behavior of black swan events may help others avoid the same outcome. In a telephone interview with E&MJ, Ross and GCE Assistant Director Chad Williams discussed how mines can de- velop a robust geotechnical program to effectively recognize and manage slope stability risks. According to Ross, the engineering staff needs access to solid geotechnical input data that supports rigorous geotechnical assessments and designs. This allows them to develop a better understanding of the risks they are managing. Identified geotechnical risks should be entered into a register and assigned appropriate controls through a "bowtie" or similar assessment. For maximum effectiveness, a mine's geotechnical team should work closely with operations personnel, he said, pref- erably with ongoing joint participation in slope-stability monitoring practices and testing. A useful tool for site-wide in- volvement is a Trigger Action Response Plan (TARP), such as the one initiated at Bingham Canyon in the months before the slide occurred. The plan comprised a five-level, color-coded set of trigger levels rated from 0 (blue, normal/stable condi- tions) to 4 (red, slide imminent or in prog- ress). The daily TARP level was sent to all employees and contractors. For each lev- el, there were separate operations, man- agement and external/security response items, consisting of the predetermined activities that could, or should, take place at each level. In addition to the overall TARP, more-detailed TARPs went out to the operations and maintenance teams. Both Ross and Williams noted that there's been a discernible rise in interest from mineral producers regarding geo- technical matters over the past several years, with corresponding increases in deployment of radars and other slope sta- bility monitoring equipment, but success in this area largely comes from having good input data for rigorous geotechni- cal design and competent engineers. The latter factor is probably the most critical at present, due to an ongoing shortage of qualified geotechnical engineers. That's where efforts such as the uni- versity's GCE will be crucial in meeting demand, said Williams. The center's pro- posed curriculum, scheduled to launch next year, will be focused on expanding the number of professionals graduating in the field, promoting professional develop- ment for existing professionals, providing training in new technology to monitor and detect potential failures, and helping to update tools and methods to understand and analyze geotechnical risks. Part of the center's focus will be aimed at preparing students to be able to attack engineering problems in an in- terdisciplinary manner and break down organizational silos that may exist. As Williams explained, lack of qualified personnel forces operators to outsource geotechnical work to consulting com- panies, which is a perfectly acceptable practice, but results in most of a mine's geotechnical knowledge residing outside the mining company. When using outside consultants on a company-wide basis, there's a possibility that the consulting firm will have a wide-ranging understand- ing of a company's geotechnical issues, but the in-house geotechnical personnel will have a much more limited view of the available information. The danger here, according to Williams, is that mine op- erators must have in-house capability to understand the risk they are managing, and to direct geotechnical work that can't be outsourced. And, he added, consult- ing firms are having their own difficulties finding qualified staff. Another GCE objective is establish- ment of a global database of "monitoring failure signatures," basically, the infor- mation provided by a site's geotechnical monitoring equipment before and after a slope failure occurred. Such a body of information, said Williams, could allow geotechnical staff and researchers to compare cross-site information and make better decisions on design, analysis and risk management. Other industry observ- ers also have noted that large data sets of this type will be needed to facilitate machine learning efforts aimed at pro- viding a reliable and accurate computer- ized method for predicting slope failures based on prior evidence. However, corpo- rate culture, competitive concerns and legal impediments can limit accessibility and sharing of such information. Until those problems are mostly resolved, it will be difficult to generate a truly global database, Williams explained. Beyond technical training and im- proved techniques for information hand- ing and sharing, engineers of the future will have to learn to cope with change, said Ross. "For example, the industry is producing 10 times more copper annu- ally now than it produced in the 1950s. Mines are starting up in regions that have never been mined in before, and the pace of production at existing mines is increas- ing dramatically. Technology is advancing at an astonishing rate. Geotechnical en- gineers of the future need to know how to cope with these challenges, and their training will have to come from a combi- nation of improved academics and ongo- ing professional development." Editor's Note: To provide slope monitoring data to the university's program or learn more about the GCE, contact Chad Wil- liams (cpwilliams@email.arizona.edu).

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