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In the process of coal-gas outburst, the gas-solid two-phase flow of pulverized coal and gas will induce large-scale damage to underground mining. In this work, in order to study the dynamic evolution law of gas-solid two-phase flow of coal-gas outburst, and clarify the short-time destructive effect of outburst dynamic phenomenon, an EDEM-FLUENT coupled model is constructed to realize the numerical simulation of coal-gas outburst two-phase flow. The simulation results show that the flow velocity of pulverized coal in a short time (tens of milliseconds) approaches to the maximum velocity rapidly, which can reach 60 m/s. The velocity of pulverized coal is inversely proportional to the particle size. The initial acceleration of particles is slow, and then the acceleration increases rapidly. The accumulation angle of pulverized coal in the outburst hole is about 21° and is far less than the natural accumulation angle of pulverized coal, which is consistent with the general phenomenon of coal-gas outbursts. The results also show that the shock wave overpressure of the coal-gas outburst of numerical simulation is similar to that of the physical simulation test, and the difference is less than 10%. And the pressure change in the roadway is completed in short time. In terms of spatial relationships, the pressure at the position closest to the outburst mouth is not the maximum, and the maximum pressure exists at a certain position away from the outburst mouth.

In order to clarify the characteristics of gas-bearing coal adsorption-instantaneous pressure relief deformation, and reveal the mechanism of the effect of gas desorption on the outburst. Through the gas-bearing coal adsorption-instantaneous pressure relief test system, the adsorption-instantaneous pressure relief test using briquette/raw coal samples was used to conduct a comprehensive comparison and analysis of the deformation characteristics of the two coal samples. Studying the damage of coal with different adsorption characteristics gases under the condition of adsorption-instantaneous pressure relief, and use strain gauges to monitor the microscopic deformation of the coal, and analysis of the adsorption of briquette/raw coal at constant pressure-instantaneous similarities and differences of deformation characteristics during pressure relief. “The results showed that under the same test conditions of adsorption equilibrium pressure, the degree of crushing of coal samples after instantaneous pressure relief is CO2 > CH4 > N2. At the moment of instantaneous pressure relief, the strain of the raw coal/briquette suddenly decreases, characterized by swelling deformation. Under the same temperature and pressure conditions, the expansion energy of CO2 is the highest, followed by CH4 and N2. Due to the raw coal has not completely destroyed the joints, only elastic deformation occurs, and the strain rises rapidly within a short period of time, resulting in shrinkage deformation. However, during the instantaneous pressure relief of the briquette, swelling and deformation occurred, and the coal was destroyed. The research results have certain significance for the exploration of coal and gas outburst mechanism.

Coal is a kind of natural pore-fracture dual medium, which determines the diffusion and seepage characteristics of gas inside under the stress conditions. In turn, the gas migration has an effect on the mechanical damage properties of coal and is closely related to the occurrence of coal-gas outburst. The occurrence of outburst is inevitably accompanied by the instantaneous displacement mutation of gas-bearing coal, which is difficult to explained by conventional plastic zone analysis. And the process from plastic failure to instability is still vague, which makes the instability critical of outburst difficult to determine. Therefore, aiming at the outburst in the working face, we put forward a progressive failure and outburst hypothesis model based on the limit analysis method of strength reduction theory. Then, the limit instability criterion of gas-bearing coal is modified, and the coal-gas outburst in the strength reduction process is simulated by using the cyclic calculation method of COMSOL software. It describes the characteristics of fluid–structure coupling and progressive failure instability of gas-bearing coal. Finally, we use the limit safety factor to describe the outburst criticality and the outburst risk. We find that the initial uncovering coal area, stress and gas pressure play an important role in controlling outburst, especially the coal stability is extremely sensitive to gas pressure changes under high stress. And based on these, the outburst prevention and control measures are put forward. The method has potential application value for the risk assessment and prevention of outburst on site.