Advancements in Reflective Seismic Tomography for the Location of Old Works and Characterization of Structural Anomalies Impacting Underground Developments

摘要

Seismic tomographic imaging, based on the same principles as a medical CAT Scan (Computer-Aided-Tomography) has been used for many years in the oil industry for large-scale subsurface stratigraphic characterization, and has most recently been applied to various structure- and stress-related problems in the coal industry. New developments in signal processing have greatly enhanced the speed, resolution, and range of applications of tomographic imaging in underground settings, and recent innovations in data acquisition hardware have further increased data reliability and repeatability. Whereas past structure mapping applications relied on seismic velocity and/or attenuation tomography within an enclosed seismic source and receiver array, recent developments in "True Reflective Tomography" (TRT~(TM)) have expanded the application of this technology considerably. For example in-seam TRT~(TM) seismic reflection may now be used to image structures and/or old workings from one general location in the mine (e.g., face areas of mains and panel developments) well ahead of planned developments-largely eliminating the need to probe-hole drill on regular intervals. This new reflective technology has also been combined with traditional cross-hole seismic tomography, providing a comprehensive, powerful tool for velocity attenuation, and reflective imaging utilizing the same source/receiver array data sets (borehole-to-borehole borehole-to-entry, and entry-to-entry). These new developments in data acquisition and image processing have greatly expanded the variety of applications for tomographic site characterization allowing the mine operator considerable flexibility to cost-effectively characterize previously inaccessible areas of the property. This paper presents examples of 2-D and 3-D seismic tomographic imaging applied to (1) the location of old works in Appalachian room-and-pillar operations, and (2) the identification of anomalous zones ahead of mining/tunneling developments. These applications demonstrate the state-of-the-art in seismic ground imaging using velocity attenuation, and reflection techniques (and combinations thereof), and further illustrate the flexibility of data acquisition from a variety of mining and tunneling settings. Recent examples are presented from projects in the United States and Europe.