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| Highwall failure at surface mine |
Background
Between 1995 and 2004, 44 miners died in slope failure accidents at surface mines in the United States. While less than 1% of reported accidents are associated with slope stability problems, slope failures were responsible for about 13% of surface mine fatalities. Research was conducted to reduce injuries and fatalities associated with slope failures in surface mines by investigating ways to minimize hazards associated with ground movements.
New technologies to improve slope stability information have been one focus of slope stability research. Hyperspectral imaging, interferometric radar, and time-lapse and video monitoring systems were developed and field tested in collaboration with other researchers (e.g., Dr. Louis Denes, Carnegie Mellon Research Institute; Dr. David Long, Brigham Young University). Prototype instruments were used to demonstrate that slope conditions and rock movements can be detected and recorded. Building on these technologies will result in practical commercial instruments to reduce hazards associated with unstable highwalls. One vendor (SiteWatch Systems, Irving, TX) now offers a trailer-mounted, solar-powered video surveillance system to mine operators after working with NIOSH researchers to develop a prototype.
A second focus of research has been to develop computer programs to assess the effectiveness of rock slope designs. Programs designed in collaboration with Dr. Stan Miller, University of Idaho, use fracture data collected by cell or line mapping on the slope to provide a probability as to whether a useful bench of a given width will be retained to catch rocks falling from upper levels.
A third focus has been to find ways to improve practices for working around mine slopes. A slope safety training video (The Sky Is Falling) was produced to improve worker awareness of the hazards associated with mine slopes. As industry uses the training materials (more than 600 copies of the video and trainer guides have been disseminated) the occurrence of injuries related to rock falls and slope failures in surface mining will decrease.
Potential Outcome
By 2010, the highwall monitoring technologies, computer programs, and user's guide promoted and developed with this research should improve the safety and reliability of slope design in fractured rocks, especially in conjunction with advances in automated fracture mapping. One immediate impact of the research has been the use of imagery to collect geotechnical data on mine slopes (Dr. John Kemeny, University of Arizona). In addition, we expect that improved effectiveness of catch benches will result in fewer injuries in mines. Special emphasis will be to continue to work with academia, particularly mining and engineering schools where design and construction of catch benches are taught.