Experimental study on the migration and distribution law of pulverized coal in roadway during coal and gas outburst

Coal and gas outburst is one of the geological disasters that seriously threaten coal mine safety production, and its main disaster forms are gas suffocation, impact and burial of pulverized coal. In this paper, the coal and gas outburst experiments under different gas pressures were carried out using the self-developed multi-functional test system for coal and gas outburst simulation. The results show that the gas entrains the pulverized coal and sprays into the roadway in a jet shape after the outburst is triggered. The gas expansion energy is under the pressure of 0.35 MPa and the initial acceleration of outburst pulverized coal is small. The migration process is significantly affected by gravity and resistance. Therefore, the migration forms are dune flow and stratified flow, and there are many “acceleration deceleration” processes, with the maximum speed of 34.2 m/s. The gas expansion energy is under the pressure of 2.00 MPa and the initial acceleration of outburst pulverized coal is large, which can effectively overcome gravity and resistance. The migration form is plug flow and the migration speed reduction is insignificant, with the maximum speed of 71.2 m/s. At the same time, when the gas pressure increases from 0.35 MPa to 0.85 MPa and 2.00 MPa, the relative intensity of outburst increases from 36.13% to 52.39% and 63.70%. The higher the gas pressure, the farther the migration distance of outburst pulverized coal, and the higher the proportion of pulverized coal in the dust collection bag at the end of the roadway, which are 65.21%, 75.05% and 87.17%. In addition, the crushing proportion of outburst pulverized coal increases with increasing gas pressure, which are 8.1%, 21.5% and 28.0%. However, there is less pulverized coal crushed with the critical particle size below 0.075 mm. Finally, the fragmentation index of outburst pulverized coal under different gas pressures are 0.19, 0.44 and 0.56, which has a good linear fitting relationship with the relative intensity of outburst. The research results have certain guiding significance for revealing the disaster causing mechanism of outburst and formulating disaster prevention and reduction measures.