Preventing falls of ground in coal mines with exceptionally low-strength roof: two case studies.
Mark-C; Molinda-GM; Burke-LM
Proceedings of the 23rd International Conference on Ground Control in Mining, August 3-5, 2004, Morgantown, West Virginia. Peng SS, Mark C, Finfinger GL, Tadolini SC, Heasley KA, Khair AW, eds., Morgantown, WV: West Virginia University, 2004 Aug; :220-227
Mines with exceptionally low-strength roof (uniaxial compressive strength < 3,500 psi and Coal Mine Roof Rating < 40) are much more likely to struggle with roof falls than other mines. Weak roof is a particular problem for many room-and-pillar mines in the midwestern and northern Appalachian coal basins. Traditional roof support techniques are often not up to the challenge at these operations. This paper focuses on two mines - one operating in the Upper Freeport Seam, the other in the Herrin No. 6 Seam. Together, the two mines had more than 300 roof falls during a recent 5-year period. Each has experimented with a variety of roof bolt types and lengths and with different supplemental supports. Detailed statistical analysis was conducted to determine which support combinations have proven to be most effective. Geology, horizontal stress, and time are also important at both mines. Successful control techniques have included (1) identifying particularly troublesome lithologic roof units, (2) installing longer and stronger roof bolts, (3) installing supplemental support in intersections, and (4) limiting how long a panel remains open. The lessons learned from these and other similar mines could help improve ground control safety for the whole U.S. mining industry.
Ground-control; Safety-research; Underground-mining; Coal-mining; Geology; Room-and-pillar-mining
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
Peng-SS; Mark-C; Finfinger-GL; Tadolini-SC; Heasley-KA; Khair-AW
Research Tools and Approaches: Control Technology and Personal Protective Equipment
Proceedings of the 23rd International Conference on Ground Control in Mining, August 3-5, 2004, Morgantown, West Virginia