In situ identification of high vertical stress areas in an underground coal mine panel using seismic refraction tomography

Because high stress anomalies can induce dynamic failures in the underground panels of coal mines, the identification of high stress areas is critically important for mining safety. We have identified areas of high vertical stress of an in-situ longwall panel with seismic refraction tomography, and interpreted our results using rock physics models constrained by core measurements. Since P- and S-velocities in rocks are stress sensitive, mapping of them can provide useful information to identify areas of potential high stress. We have inverted P- and S-velocities of main roof of an in situ panel with refraction tomography, and converted them into vertical stress estimates using a calibration function from core measurements. Those estimates are classified into three groups (high, medium, and low), respectively. Identified zones of high vertical stress show qualitative agreement with monitored in-panel microseismic data. Zones derived from P-waves give a more plausible assessment than S-waves. We also discuss the link between high vertical stress areas and in-panel faults. Because of the impact of the regional stress field and previously mined out voids, the existing fault zone affects the redistribution of vertical stress in the underground panel.