Local earthquake tomography for imaging mining-induced changes within the overburden above a longwall mine.
Westman EC; Luxbacher KD; Swanson PL
42nd U.S. Rock Mechanics Symposium/2nd U.S.-Canada Rock Mechanics Symposium, June 29 - July 2, 2008, San Francisco, California Alexandria, VA: American Rock Mechanics Association, Paper No. 08-299, 2008 Jun; :1-7
Three-dimensional velocity tomograms were generated on a daily basis to image mining-induced changes to the overburden above a longwall mine. The hypothesis was that a coherent redistribution of seismic velocity, due to the development of high-stress zones, could be imaged at the mine scale. Seam depth was 360 m and source location depth varied from 100 to 1000 m. Sixteen geophones were distributed over a 600 by 600 m square area on the surface above the mine. More than 12,500 events were recorded over an 18 day period. The recorded seismicity provided input for the local-earthquake tomography code, SIMULPS. Eighteen tomograms were generated and high-velocity regions correlated well with high abutment stresses. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated. These results indicate that velocity tomography can be used to provide a better understanding of temporal changes within a rock mass, and can potentially be used to produce a better understanding of the mechanisms that lead to unanticipated ground failures.
Rock-mechanics; Ground-control; Ground-stability; Geology; Engineering-controls; Models; Computer-models; Mining-industry; Underground-mining; Longwall-mining
42nd U.S. Rock Mechanics Symposium/2nd U.S.-Canada Rock Mechanics Symposium, June 29 - July 2, 2008, San Francisco, California