Influence of Geo-stress on Dynamic Response Characteristics of Coal and Gas Outburst

The influence of tectonic, geostatic, and mining stresses on coal and gas outburst (CGO) becomes more obvious with increasing mining depth. The limitations of general experimental methods and test systems hinder the direct observation and characterization of the dynamic responses of the multi-physical parameters associated with CGO. In this study, a custom-made large-scale physical simulation test system was used to study the characteristics of outburst evolution under different geo-stress levels, to overcome dynamic disasters in coal mines. The intensity and initial velocity of the outburst coal flow increased with increasing geo-stress. The geo-stress changes and gas pressure released during the outburst process mainly manifested in the relief and abutment stress zones, while the release of the elastic strain energy manifested in the abutment stress zone. This showed that the sphere of influence of the change on the physical parameters, such as the geo-stress, gas pressure, and elastic strain energy, is important for setting the drilling depth in measures to eliminate outburst. Interestingly, there seems to be a mechanism that suppresses the excess energy released during the outburst process, such that the solid–gas ratio of the two-phase outburst flow does not increase with increasing initial geo-stress. The dynamic outburst phenomenon is not completely positively correlated with increasing geo-stress. The mechanism causes cyclical fluctuations in the geo-stress, elastic strain energy, and gas pressure during the CGO process and pulse characteristics of the outburst coal flow simultaneously.