Pillar design for deep cover retreat mining: ARMPS version 6 (2010).
Proceedings of the Third International Workshop on Coal Pillar Mechanics and Design, Morgantown, West Virgina, July 26, 2010. Pittsburgh, PA: National Institute for Occupational Safety and Health, 2010 Jul; :104-120
In the wake of the Crandall Canyon mine disaster, the National Institute for Occupational Safety and Health (NIOSH) revisited the issue of pillar design for deep cover retreat mining. Studies conducted at 30 mines added more than 200 new case histories to the Analysis of Retreat Mining Pillar Stability (ARMPS) database. Extensive statistical analyses were supplemented with numerical modeling using Boundary Element and Finite Difference techniques. The analysis focused on the development of a "pressure arch" loading model for ARMPS. A previous study, published in 2002, had found that pillar designs under deep cover could be successful with lower ARMPS stability factors. The current study concluded that the most likely explanation is that a pressure arch forms above a deep panel, transferring some of the load from the production pillars to the barrier pillars. The analysis showed that the statistical "best fit" pressure arch algorithm results in recommended pillar sizes that are very similar to those suggested by the 2002 guidelines. It represents a significant improvement, however, because: a) It provides a rational explanation for the observed success of smaller pillars at depth, and b) It recognizes the inherently greater stability of narrow panels at depth, and incorporates panel width into the design guidelines. The revised loading model has been implemented in an updated version of the ARMPS computer program, called ARMPS Version 6 (2010). For most shallow cover situations, where the panel width exceeds the depth of cover, ARMPS Version 6 (2010) is identical to ARMPS 2002. Other statistical analyses explored the effects of roof strength, coal strength, and geographic location on the likelihood of pillar design success. None of these factors was found to be highly significant. New guidelines for determining ARMPS input values for the depth of cover and the mining height are included as an appendix.
Mining-industry; Underground-mining; Geology; Rock-mechanics; Room-and-pillar-mining; Models; Computer-models; Statistical-analysis; Risk-analysis
Proceedings of the Third International Workshop on Coal Pillar Mechanics and Design