Mapping hazards with microseismic technology to anticipate roof falls: a case study.
Iannacchione-AT; Batchler-TJ; Marshall-TE
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; :327-333
As the number of new fractured surfaces or "damaged rock layers" within roof rock increase, the stability of the rock mass decreases. Although direct measurements of this phenomenon are not easily made, there is good circumstantial evidence to support this hypothesis. For example, it is common to observe increased cracks or fractures in the immediate mine roof rock before a roof fall. Likewise, roof drill holes placed in areas that later fail often reveal increased numbers and/or separations of fractures within the rock column over time. Finally, the frequency of microseismic activity, representative of rock fracturing, increases before a roof fall. For this study, more than 700 microseismic emissions were collected from two underground limestone mine roof fall areas in southwestern Pennsylvania. Microseismic events were located and magnitudes determined using the moment magnitude technique. Moment magnitude is based on the event seismic moment, which is a measure of the seismic deformation. The amount of new fracture surface length was calculated based on the stored strain energy within the rock before fracture. In the two case studies presented, a significant amount of microseismic activity was observed as much as 2 days before the first signs of failure in the roof fall areas. In addition, results from this analysis reveal much about the behavior of strata prone to failure and allow for the construction of hazard maps based on microseismic emissions. The potential use of this technique as a means of anticipating roof falls is analyzed and discussed.
Ground-control; Safety-research; Underground-mining; Stone-mines; Room-and-pillar-mining; Hazards; Geology
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