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More than 80% of U.S. roof bolts are fully-grouted, but about 1500 roof falls are reported each year. Anchorage failure of a fully grouted bolt can occur when the roof is active near the top of the hole. This paper reports on an extensive series of short-encapsulation pull tests (in which the bolts are installed with only 1 ft of resin) that were conducted in the National Institute for Occupational Safety and Health (NIOSH) Mine Safety Research Laboratory and operating mines in WV and PA. The tests confirmed that poor anchorage can be encountered under some weak rock conditions. Suggestions for improving anchorage are included.
| Author(s): | Mark-C, Compton-CS, Dolinar-DR, Oyler-DC |
| Reference: | 2003 SME Annual Meeting, Feb 24-26, Cincinnati, Ohio, preprint 03-138. Littleton, CO: Society for Mining, Metallurgy, and Exploration, Inc., 2003 Feb; :1-8 |
fptof (PDF, 334 KB)
