Assessment of the influence of the surface layer of coals on gas-dynamic phenomena in the coal seam

Purpose. Development of physical and mathematical model linking nanostructured surface layer of coal substance with geodynamic phenomena of coal seam, through adhesion energy of different layers and coal grades, melting temperature of the nanolayer, determination of the role of stress-strain state of the seam in the formation of fine coal and methane at their emissions into the mine workings. Methodology. Mathematical and experimental studies of the regular change in the surface layer of coal substance depending on the grade of coals for different formations of the Karaganda basin; assessment of the influence of the surface layer of coal on the adhesion energy, which determines the stress-strain state of the coal seam. Physical methods for studying the decomposition temperature of methane-bearing coal seams, changes in its concentration, reaction rate of methane release from coals. Findings. A regular decrease in the thickness of the surface nanolayer of coal substance in different coal grades and formations in the metamorphic series of coals is shown. It has been found that this decrease is accompanied by an increase in surface energy and adhesion energy. The connection of gas-dynamic phenomena with stress-strain state of coal seam, which forms fine-dispersed structure of coal, forms of methane location, activation energy of solid coal-methane solution, rate of thermal decomposition reaction, critical stresses determining development of cracks in coal substance is shown. Originality. For the first time, a physical model for calculating the thickness of the surface nanolayer and its surface energy for coals of different grades of the Karaganda basin has been developed; the relationship between the thickness of the nanolayer and the melting temperature, adhesion energy, linking the stress-strain state of the coal bed in the zone of gas-dynamic phenomena and the concentration of methane has been established. The value of internal stresses in the surface layer of coals of different grades has been found to be a constant value. Connection of activation energy of decomposition of solid coal-methane solution from Gibbs energy and methane concentration, which explains its significant amount in gas-dynamic phenomena, has been established. Practical value. The physical and mathematical model describes the influence of surface coal on the processes occurring in the zone of gas-dynamic phenomena and the regularities of their changes depending on the thickness of the surface nanolayer determining such parameters as: stress-strain state, dispersion of coals, as well as the release of a large amount of methane at the sudden release of coal gas into the mine workings.