Microseismic and electromagnetic coupling method for coal bump risk assessment based on dynamic static energy principles

Electromagnetic emission (EME) and micro-seismic (MS) monitoring are two most important and commonly used geophysical methods for coal bump monitoring in China coal mines. Research have proved during the preparation and development of coal bump the EME can represent energy accumulation in coal seam, while MS have a duality of stress concentration and energy release. And Field investigations have revealed that coal bump events occurred in longwall coal mines manly induced by static coupling dynamic loads. So it is much more valuable and useful for risk evaluate if these two methods synthesized together. Based on energy principles the precursory rules of coal bump are studied in this paper combining with the EME and MS monitoring, the coupling evaluation system was established based on the monitoring results of a specific coal bump colliery, the critical values of EME and MS are formulate based on laboratory test and a large number of site investigation that more than 100 mines in China. A typical precursory of coal bump is that the EME strength exceeds the critical value while total MS energy maintains a low lever at the same time the number of tremors appears an increase tendency. The risk will be gradually reduced when the MS events keep a steady energy release under the critical value even though the EME strength is higher. The research outcomes also provide a foundation for the control and effect inspect of coal bump.