“…On the basis of the established recovery flow-solid coupling model, relevant experts and scholars have conducted research on borehole gas extraction. In terms of numerical simulation, the influence of ground stress factors on permeability is very significant, and a multistage pore fluid–solid coupling model considering the influence of ground stress factors on gas seepage is established; , flow-solid coupling mathematical models of coal and gas protrusion considering moisture, stress damage, and permeability coefficient factors are established; − flow-solid coupling models of multiphysical field coupling considering different physical field factors are established; , experimental study of coal permeability was carried out under consideration of effective stress, matrix expansion/contraction, and gas slip factors, , and then, matrix expansion/contraction factors were provided to the coal seam gas transport flow-solid coupling model. , In terms of gas extraction from boreholes, the extraction radius of underground gas extraction boreholes is deduced by numerical simulation method and verified on site; , gas migration characteristics of coal seam considering high-stress factors are studied, and the mechanism of gas extraction efficiency improved by pressure relief mining technology is further elaborated; considering the influence of the number of boreholes on gas extraction, the pressure sensor was used to monitor the change of gas pressure under a different number of boreholes; the theoretical equation of the plastic zone radius considering the plastic deformation factor was established, and the effective radius of gas extraction in the plastic zone was determined; considering the factor of water content, different water content factors are provided to study the change of gas pressure in coal seam gas extraction . In terms of laboratory experimental research, different physical and chemical factors of the coal body are considered to carry out experimental studies on the seepage characteristics of different coal steps, and the gas transport characteristics of the coal body under different fracture scales are studied. − Based on the self-developed coal triaxial seepage instrument and low-field NMR instrument, the adsorption characteristics and pore size distribution characteristics of different coal ranks were studied, and the seepage characteristics of different bedding coal bodies were obtained. − From microscopic and macroscopic perspectives, it can reveal the coal pore size distribution and gas transport characteristics comprehensively from microscopic and macroscopic perspectives, which is of guiding significance for coal seam gas extraction.…”