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In order to improve the dust control efficiency of swirling air curtain in fully mechanized excavation face and reduce the pollution of high concentration dust, this paper analyzes the influence of dust extraction area on swirling air curtain dust control by combining numerical simulation with engineering measurement. The results show that with the increase of the distance between the air extraction vent and the working face, the farther the air extraction duct is from the side wall of the roadway opposite to the air compression duct, the lower the dust control ability of the working face flow field, and the higher the diffusion distance and diffusion angle of the high concentration dust. Based on the simulation results, it is determined that the optimal dust extraction area of the swirling air curtain dust control in the fully mechanized excavation face is 2 m away from the working face, and the air extraction duct is installed on the side wall of the roadway opposite to the air compression duct. Through engineering application, the validity of the numerical simulation conclusion is verified. The dust concentration at the driver of driving machine can be reduced to 24.6 mg/m3, the dust control efficiency of the air curtain reaches 91%.

In order to analyze the influence of unsteady diffusion characteristics of tectonic coal on energy instability, the steady and unsteady gas diffusion models were used to establish the functional relationship between the initial gas diffusion coefficient and pressure of intact coal and tectonic coal. Based on the existing energy formula, the calculation models of adsorbed gas and free gas expansion energy were established. The relationship between buried depth and outburst energy was analyzed, and the instability tendency of outburst energy in coal under different buried depths was discussed. The critical buried depth of outburst in the tectonic coal seam was 190 m, and the field gas dynamic phenomenon also verified the conclusion.

In order to provide a comprehensive reference for the study of carbon dioxide displacement of coalbed methane, this paper explores the influence of different influencing factors on coal adsorption capacity, analyzes the gas migration and adsorption principle in coal bed, as well as the difference and relationship between different adsorption models, and introduces the pilot test and application of CO2-enhanced coalbed methane recovery in different countries. Using VOSviewer software and CNKI metrological visualization analysis function, this paper analyzes the annual publication trend and keyword time trend of CO2-ECBM related literature in CNKI and Web of Science databases, and discusses the problems existing in CO2-ECBM. The results show that coal rank and pore structure, temperature and pressure, moisture content and other factors can affect coal adsorption capacity in different forms. Gas migration in coal seam is a complex system composed of adsorption/desorption-diffusion-seepage. The best adsorption model should be considered in studying coal adsorption gas. Based on VOSviewer analysis, CO2-ECBM research is a hot topic in China. The research direction has gradually shifted from macroscopic geological storage evaluation to reveal the mechanism of coal storage and displacement gas from microscopic or molecular levels such as pore structure and composition of coal, and multi-field coupling simulation of CO2-ECBM.

In order to reduce the coal dust pollution when the heavy train enters the tunnel and to ensure the safety of railroad operation, this paper adopts numerical simulation to study the characteristics of the wind flow field of the heavy train passing through different shapes of tunnels. The results show that the shape of the tunnel section has a significant effect on the piston wind characteristics of the train entering the tunnel. When the train passes through the tunnel, the value of the wind pressure and the gradient of the pressure on the surface of the carriages increase from horseshoe shape, high wall shape and high arch shape. The vortex structure generated at the entrance of the horseshoe tunnel is the smallest and the flow field is more stable, and the wind turbulence shows significant weakening effect; when the rear end of the car enters the tunnel, the range of the influence of the piston winds outside the tunnel is in order of smallest to largest for the horseshoe, high wall, and high arch tunnels; in the wake region, the central region of the strong vorticity zone in the horseshoe tunnel is more continuous, reducing the instability of the airflow in the tunnel. The results of this study are of great significance in understanding the characteristics of the wind flow field and the effect on dust generation when heavy trains pass through the tunnel.

In order to improve the dust-resistance efficiency of radial swirling air curtain in fully mechanized excavation face and prevent high-concentration dust pollution on the working area, the method of combining numerical simulation and engineering measurement is used to analyze the influences of ventilation conditions on dust-resistance rule of radial swirling air curtain. The results show that as the distance between the air curtain and the working face increases, the radial air volume of the air curtain device increases, and the pressure-exhaust ratio of the ventilation system decreases, the radial swirling air curtain is easier to transform into an axial direction with uniform air volume and velocity distribution during the migration process, and the dust pollution degree reduces as well. Fitting the quantitative relationship between the high-concentration dust diffusion distance and various ventilation conditions, combined with the actual production conditions, it is determined that the better ventilation conditions for the radial swirling air curtain dust resistance are as following: the air curtain is 30 m away from the working face, the radial air volume of the air curtain device is 270 m3/min and the pressure-exhaust ratio of the ventilation system is 0.8. Through engineering measurement of the simulation result, the validity of the numerical simulation was verified. The dust concentration ofthe tunneling driver’s section was reduced to 35.5 mg/m3, and the air curtain dust resistance efficiency reached to 90.5%.

To grasp the pressure and failure deformation and stress distribution of the underlying coal seam during the mining process of the protective coal seam, and improve the effect of the upper protective coal seam mining to prevent the coal seam and gas outburst of the underlying coal seam, this paper takes the Ⅵ16-17 coal seam of Pingdingshan No.4 mine in Henan Province as the object. Based on the Poyting-Thomson model, the creep dynamics model of coal and rock mass is constructed. The Comsol Mutiphysics 5.2 is used to simulate the deformation and deformation law of the underlying coal seam and the engineering verification. The results show that with the advancement of the upper protective layer working face (from 10 m to 60 m), the left and right sides of the underlying coal seam form a relief angle of 98.5° and 114° respectively, and the lateral plastic deformation increases to a maximum of about 216 m; the coal seam is characterized by plastic deformation to deformation recovery, which indicates that the exploitation of the upper protective layer contributes to the formation of gas depressurization channels in the underlying coal seam, which is beneficial to the extraction of gas in the underlying coal seam.