Seismic Tomography To Map Hazards Ahead Of The Longwall Face

Anomalous geologic or stress conditions ahead of a longwall face have the potential of causing great harm to both the individual miner and the mining operation as a whole. NSA Engineering has been developing seismic tomography techniques to image the panel ahead of the face. This paper presents the results of afield effort in which a 60-m (200-ft) segment of a longwall panel containing a fault zone was surveyed daily as the face approached. Stress distribution, geologic structure and dynamic elastic properties within the panel were plotted and compared to static laboratory measurements. The surveys successfully imaged an anomalous stress concentration that was likely influenced by the presence of the fault zone. The calculated dynamic physical properties generally agreed with the laboratory measurements.