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| Portable shotcrete panel tester |
Background
Falls of ground are one of the leading causes of injuries and fatalities in underground mines. During the 1990’s, gold mining expanded significantly in Nevada. Most of the geological formations are in weak rock, and the occurrence of injuries caused by rock falls doubled.
NIOSH collaborated with several underground gold mines in Nevada to evaluate the use of fiber-reinforced shotcrete against the standard application of steel screen and shotcrete. The amount of fibers was varied to determine the amount that would produce optimum support performance. To conduct this work, an Australian round panel testing system was designed, built, and tested. This system gives mines the capability of testing shotcrete in situ to optimize the design and engineering parameters of the support application. The field test confirmed there were statistically significant improvements in ground control when fiber-reinforced shotcrete was used and subsequently improvements in the safety of the underground miners. Several other mines in Nevada have utilized these tests to improve their underground support. The panel tests conducted at the mine showed positive results for initial failure and energy absorption. With this testing program, mine engineers can determine the characteristics of the shotcrete on site.
Potential Outcome
The application of fiber-reinforced shotcrete as an alternative to shotcrete reinforced with steel screen reduces worker exposure to potential rock falls and to materials-handling injuries by eliminating the time and manual labor involved in placing screen panels during installation. Research results also indicate that fiber is more effective in reinforcing shotcrete and thus improves the performance of primary support. When this research is completed, design criteria will be published to guide selection and application of shotcrete as a means of rock support. As this technology is adopted and applied by the mining industry over the next 5 years, fewer injuries caused by rock falls should result.