Integrated monitoring and analysis techniques for evaluating longwall panel ground behavior

The rapid identification of ground hazards developing ahead of a mechanized longwall face is necessary for safe and efficient coal mining. The U.S. Bureau of Mines is devising improved methods to detect ground hazards through the development of an integrated real-time monitoring and analysis system. A Ground Control Management System and an Automated Microseismic Monitoring System were previously developed by Bureau researchers, and both systems were jointly field tested in a western coal mine during 1993. Source energy distributions of microseisms were calculated with event locations normalized to face position. These distributions show activity changes with distance from the face, across the panel, and in the support pillars as mining progressed. Although most microseismic activity was in the vicinity of the face, enough activity occurred ahead of the face to show that the tailgate becomes microseismically active 30 to 90 meters prior to mining. Comparisons between pillar pressure measurements and microseismic energy generated in and above the pillars correlate well with increases in pillar pressures. Large energy microseismic events were also compared over time with shield pressures. This analysis indicates that a space-time correlation may exist between the advance of the face in the tailgate and the occurrence of large microseismic events.