Retreat mining with mobile roof supports.
Chase FE; McComas A; Mark C; Goble CD
Proceedings: New Technology for Ground Control in Retreat Mining, Pittsburgh, PA: National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 97-133, IC 9446, 1997 Mar; :74-88
Mobile roof supports (MRS's) are shield-type support units mounted on crawler tracks. MRS's are used during retreat mining and eliminate the setting of roadway, turn, and crosscut breaker posts that are required during pillar recovery operations. Mobiles are a more effective ground support than timbers, and their usage enhances the safety of section personnel and reduces material handling injuries. MRS usage is rapidly increasing, and approximately 40 U.S. coal mines have successfully employed this relatively new technology. This paper addresses the practical aspects of MRS usage in underground coal mines. During this study, nearly one-half of the U.S. mines that have utilized mobiles were visited. This report depicts the more common pillar extraction methods that operators have found successful. The "Christmas tree" and outside lift methods are described and illustrated. Roof control plans that do not require breaker posts or allow pillar extraction with fewer than four mobiles are also examined. In addition, operators' experiences with setting pressures, loads, and rates of loading during pillar extraction are addressed. Mining and support strategies to more effectively control hillseams, weak roof, and gob overrides are also discussed.
Mining-industry; Underground-mining; Accident-prevention; Coal-mining; Mining-equipment; Injury-prevention
Proceedings: New Technology for Ground Control in Retreat Mining