Reasonable Width of Narrow Coal Pillars Along Gob-side Driving Entries in Gas Outburst Coal Seams: Simulation and Experiment

In gob-side entry driving, the coal pillar width determines the stability of the surrounding rock and the pillar itself. Thus, to improve the stability of gas outburst coal seams, the reasonably narrow width of the coal pillars of the 40403 working face of the Shengyuan coal mine 4# was theoretically determined. Through two-dimensional simulations, the surrounding rock stability for a roadway with different coal pillar widths was evaluated. The mechanism of the surrounding rock displacement and stress distribution with the increase of the coal pillar width was also defined; for pillar widths of 2–4, 4–6, and 6–10 m, the vertical stress distribution was approximately triangular, trapezoidal, and parabolic, respectively. The coal pillar displacement was significantly greater on the goaf side than on to the roadway side. As the width of the coal pillar was incremented, its displacement on the goaf side increased, while that on the roadway side remained relatively small. The combination of the simulation results with on-site measurements finally revealed that 5 m is a reasonably narrow coal pillar width. Then, the findings were successfully applied to the 40403 working face of the Shengyuan coal mine 4#, achieving good outburst prevention and cost reduction.