Mine pressure behavior laws and stability control of isolated face gob-side entry under the influence of variable width coal pillar

The width of the coal pillar has a significant impact on the stability of roadway surrounding rocks and the effectiveness of support. To study the effects of coal pillar width variations on the stress distribution, plastic zone evolution, and support in the roadway surrounding rock, this paper combines numerical simulations, theoretical analysis, and field measurements to investigate the stress, plastic zone, and support force of the roadway surrounding rock throughout the entire mining process under varying coal pillar widths. A mechanical model of the roadway surrounding rock under changing coal pillar widths is established, simulating the stress distribution, plastic zone development, and surrounding rock deformation process for different coal pillar widths. The study analyzes the impact of coal pillar width variation on stress concentration, fracture propagation, and plastic zone evolution. In terms of field measurements, monitoring points are set at working faces with different coal pillar widths to collect data on stress, displacement, and other factors for validating the results of numerical simulations. The study results indicate that as the coal pillar width increases, the stress in the coal pillar exhibits a “first increase-then decrease-then increase again-then decrease” bimodal phenomenon from the roadway side to the goaf side, with the stress concentration on the roadway side being smaller than on the goaf side. During tunneling, when the coal pillar width is 27.0 m, the stress concentration coefficient is the smallest （2.37）, while during extraction, when the coal pillar width is 17.4 m, the stress concentration coefficient is the largest （5.16）. Regarding surrounding rock deformation, the working face with a coal pillar width of 17.4 m shows the greatest deformation, with the convergence amount of both sides being 282.40 mm and the top and bottom convergence being 374.30 mm during the initial mining stage. The study demonstrates that increasing the coal pillar width helps to slow down the development of the plastic zone and suppress the propagation of fractures. The numerical simulation results are consistent with the field measurements, validating the effectiveness and reliability of the numerical model. The research reveals the influence of coal pillar width variation on the stress and deformation of roadway surrounding rocks, providing theoretical and simulation-based support for optimizing coal pillar width. This research offers theoretical predictions for the mining pressure manifestation in isolated faces and provides valuable insights and references for similar conditions in roadway excavation.