To accurately determine the effective extraction radius of directional long drilling, the influence of the negative pressure of the hole mouth, the drilling diameter, and the drilling length of the hole on the effective extraction radius of a directional long drilling hole is simulated by establishing a coal-to-gas gas structure coupling model considering the Klinkenberg effect. Finally, the reliability of the numerical simulation is verified through field testing in Yuxi Coal Mine. The results reveal that the attenuation of negative pressure in a directional long borehole along a long hole has a significant influence on the gas extraction effect. The radial gas pressure of the extraction drilling hole is distributed in a "V" shape when the negative pressure of the extraction decays along the direction of the hole length. The higher the negative pressure and the longer the diameter of the drilling hole, the higher is the gas extraction effect. The effective extraction radius is exponentially related to the drilled hole depth when the negative pressure of extraction is attenuated along the long hole direction. The negative pressure of the hole and the diameter of the borehole are linearly related to the effective extraction radius at the depth of drilling hole of 430 m. Through field tests, while extracting for 180 days based on the stubble pressing effect, the effective extraction radius of the directional long borehole of the No. 3 coal seam of Yuxi Coal Mine is 5.7 m, and the absolute error between the numerical simulation is 0.1 m. In addition, the gas pressure obtained from different sampling points is consistent with the numerical simulation. The relative error is 0.3-4.1%. The results provide a theoretical basis for the rational layout of directional drilling.

Owing to differences in deformation characteristics of roadways with different section shapes and depths, it is difficult to determine the support form and grouting depth of a roadway, which can cause serious deformation to the roadway. To address the challenges in determining the shape and grouting depth of a roadway section when the mine depth is known, the loose zone range of the roadway was tested using the acoustic method, and the loose zone evolution law under different conditions was performed by numerical simulations. The research results revealed that when the ratio of the maximum principal stress to the minimum principal stress is eta > 3, the distribution of the rock loosening zone under different cross-sectional shapes was roughly "butterfly-shaped", and the "smoother" the cross section in the design of the roadway, the smaller the range of the rock loosening zone. With the increase of burial depth, the rock loosening zone and sealing depth also increase; the rock loosening zone and burial depth have a power function relationship the rock loosening zone range = a.burial depthb; the sealing depth and burial depth have a linear relationship R = aH + b.

Coal seam gas drainage is a primary measure for mitigating coal and gas outburst hazards. Grouting sealing can form coal-slurry consolidated bodies, significantly improving the sealing quality of gas drainage boreholes and alleviating coal and gas outburst risks. Therefore, this study conducts triaxial loading and seepage experiments to analyze the mechanical failure characteristics and permeability variation of coal-slurry consolidated bodies under loading conditions following grouting sealing of gas drainage boreholes. Based on the “cube” model, a permeability model for the damaged coal-slurry consolidated body under loading conditions is established. The findings provide guidance for evaluating the leakage prevention performance of sealing materials in field engineering and optimizing the sealing efficiency of grouting materials. Future research may explore the damage and seepage evolution of coal-slurry consolidated bodies under various loading conditions and sealing material types.

Previous studies studying hydraulic flushing technology for gas extraction, the surrounding rock is often simplified to an isobaric state, and the failure of coal is also analyzed using the Mohr–Coulomb model, which is inconsistent with the field. To solve this problem, we analyzed the strain-softening model and derived a formula for the distribution of plastic zones in the surrounding rock of boreholes, considering strain-softening. Theoretical analysis was conducted on the influence of the lateral stress coefficient and cohesion in the crushing zone on the plastic zone, and verified it with the numerical model. Furthermore, the distribution law of the plastic zone in the surrounding rock of hydraulic flushing boreholes, considering strain-softening and bidirectional non-axisymmetric stress, was explored by changing the borehole diameter. The research results show that the lateral stress coefficient affects the distribution pattern of the plastic zone, and the cohesion of the crushing zone affects the size of the plastic zone. As the diameter of the borehole increases, the difference between the plastic zone radius calculated by the strain-softening model and the Mohr–Coulomb model gradually increases, indicating that the larger the borehole diameter, the greater the error in the plastic zone obtained by the Mohr–Coulomb model. This indicates that the strain-softening of the surrounding rock should be considered when studying the plastic zone of the surrounding rock in a hydraulic flushing borehole under non-axisymmetric conditions. The relevant research results provide a basis for the subsequent use of numerical simulation methods to study the permeability and gas flow law of the surrounding rock in hydraulic flushing, considering strain softening.