Study on the Optimization of Coal Pillar Width in Goaf-Side Roadway Under the Synergistic Effect of Mining and Seepage

In coal mine roadways excavated along the goaf with water accumulation, the roadway is subjected to the combined effects of water infiltration and multiple stresses from excavation activities, leading to significant deformation and challenges in determining the appropriate coal pillar width. This study, based on the Jianxin Coal Mine 4301 tailgate, utilizes the advanced three-dimensional numerical calculation software FLAC3D 6.0 to develop a comprehensive seepage flow model. By analyzing the distribution of key roadway surrounding rock properties, such as deviatoric stress, plastic zone, and dissipated energy, the influence of coal pillar width on roadway deformation and failure characteristics is systematically investigated. The findings provide novel insights into the roadway stability control under complex geological conditions. Specifically, the results reveal that: (1) When the coal pillar width is less than 9 m, stress concentration zones are observed, fully connected by plastic zones and dissipated energy. For widths exceeding 9 m, the influence of the goaf diminishes, leading to a stress reduction zone within the coal pillar and a shift in dissipated energy density distribution from a penetrating shape to an independent double-core shape. The plastic zones on both the goaf and roadway sides become independent, indicating a transition from an unstable to a stable coal pillar state. (2) Using the Analytic Hierarchy Process (AHP), a zoning control system for the roadway surrounding rock is established, dividing the roadway into three regions: normal support, reinforced support, and special support. Industrial experiments corroborate the simulation results, and on-site monitoring demonstrates that the control measures significantly improve roadway stability. This study presents an innovative approach to the design and control of coal pillars in water-affected mine roadways, offering valuable contributions to both the scientific understanding and practical application of mining engineering in similar geological settings.