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Abstract Coal and gas outburst is a complex dynamic disaster during coal underground mining. Revealing the disaster mechanism is of great significance for accurate prediction and prevention of coal and gas outburst. The geo-dynamic system of coal and gas outburst is proposed. The framework of geo-dynamic system is composed of gassy coal mass, geological dynamic environment and mining disturbance. Equations of stress–damage–seepage interaction for gassy coal mass is constructed to resolve the outburst elimination process by gas extraction with boreholes through layer in floor roadway. The results show the occurrence of outburst is divided into the evolution process of gestation, formation, development and termination of geo-dynamic system. The scale range of outburst occurrence is determined, which provides a spatial basis for the prevention and control of outburst. The formation criterion and instability criterion of coal and gas outburst are established. The formation criterion F 1 is defined as the scale of the geo-dynamic system, and the instability criterion F 2 is defined as the scale of the outburst geo-body. According to the geo-dynamic system, the elimination mechanism of coal and gas outburst—‘unloading + depressurization’ is established, and the gas extraction by boreholes through layer in floor roadway for outburst elimination is given. For the research case, when the gas extraction is 120 days, the gas pressure of the coal seam is reduced to below 0.4 MPa, and the outburst danger is eliminated effectively.

Coal mine safety accidents are very likely to occur when the roadway is excavated through tectonic areas such as collapsed pillars. In this paper, Rayleigh wave technology is used to carry out advance detection in heading face of No.8 joint roadway in Zhangcun Coal Mine 480# mining area. Firstly, the phase velocity of the wave is calculated based on the simple harmonic fluctuation displacement equation and spectral analysis technique, and the dispersion curve is obtained by theoretical calculation with the phase velocity as the horizontal coordinate and the half-wavelength of the wave corresponding to the phase velocity as the vertical coordinate. Based on the finite-difference （FDM） method, we obtained that Rayleigh waves would gather energy at the junction of the collapse column and the surrounding rock, and verified that the Rayleigh wave energy decays slowly and propagates slowly. Secondly, according to the mine geological data and the actual production situation of roadway excavation, it is determined that the overall observation distance is 3.5 m to carry out the Rayleigh wave geological structure detection. Finally, using the comprehensive analysis method of the dispersion curve and the coal seam depth profile, it is concluded that there are 3 anomalies in the geological structure of the 8# connecting roadway in Zhangcun Coal Mine, which are located at 20-30 m, 35-45 m, and 55-65 m respectively. The results of this study effectively guide the safe driving of No.8 combined roadway.