Fracture Detection With Sellsmlc Crosshole Tomography For Solution Control In A Stope

As part an environmental assessment for the application of in situ leaching in an<br>underground mine, the U.S. Bureau of Mines conducted a seismic crosshole tomographic<br>investigation at the Colorado School of Mines experimental mine near Idaho Springs, CO.<br>Seismic tomography was used to detect fractured regions as part of an investigation aimed at<br>providing information that will help mining companies control solution during stope leaching.<br>Whole waveform data provided both direct P-wave and S-wave traveltimes for input to the<br>Bureau’s curved ray tomography program MIGRATOM, based on Huygens’ principle of<br>wavefront propagation.<br>The heterogeneous velocity distribution observed is attributed to the presence of both<br>natural and blast induced fractures. The effectiveness of the tomographic method was<br>corroborated by noting that low velocity zones occurred where water was lost in boreholes.<br>The pre- and post-blast P-wave tomograms showed similar velocity distributions. This<br>similarity in velocity tomograms suggests that the blast energy was contained resulting in<br>minimal extension of existing fractures. Where changes in velocity were observed, they<br>correlated to either natural fractures or blast induced damage. Tomograms also were<br>produced showing the variation in dynamic elastic properties, including Poisson’s ratio,<br>Young’s, shear, and bulk moduli. Such dynamic elastic properties assist in solving<br>engineering problems associated with deformation, stability and blast design.