Investigation of pillar-roof contact failure in northern Appalachian stone mine workings.
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; :320-326
The roof rock in underground limestone mines in northern Appalachia can be subject to high horizontal stresses despite the shallow depth of the workings. The high stresses can cause roof stability problems. NIOSH researchers have observed a distinctive, asymmetrical mode of failure at the pillar-roof contact in two underground stone mines, which is different from the typical failure mode observed in response to excessive levels of horizontal stress. A dip of greater than 5 deg was identified as a possible cause of this mode of failure. Numerical model experiments showed that an increase in the dip of the workings can cause an increase in the stress at the up-dip corner of the roof beam. A case study is presented in which failure at the pillar-roof contact was observed where the dip of the workings was 7 deg in a high horizontal stress field. Numerical modeling showed that the relatively small dip of the workings could have induced stress changes in the immediate roof that would explain the failures. The model results also showed that this mode of failure is less likely to occur if the limestone pillars contain weak bedding planes that provide stress relief. In addition, the results showed that for the conditions at the case study site, the stress in the roof beam was not sensitive to the thickness of the roof beam or the excavation span. The high horizontal stresses at this site are an important contributing factor to the observed failures.
Ground-control; Safety-research; Underground-mining; Stone-mines; Models
NIOSH Pittsburgh Research Laboratory, P.O. Box 18070, Pittsburgh, PA 15236
Peng-SS; Mark-C; Finfinger-GL; Tadolini-SC; Heasley-KA; Khair-AW
Disease and Injury: Traumatic Injuries
Proceedings of the 23rd International Conference on Ground Control in Mining, August 3-5, 2004, Morgantown, West Virginia