Research on Optimal Width of Coal Pillars in Both Sides of Abandoned Mining Areas and Tunnel Control Technology

ABSTRACT Aiming at the key technical challenge of determining the reasonable width of section coal pillars and controlling roadway stability in the island face, this study takes the 4 2 201 face of Shengxin Coal Mine as the engineering background. By integrating theoretical analysis, numerical simulation, and field practice, a systematic investigation was conducted on the principles for determining the reasonable pillar width and the corresponding roadway control technology. The study analyzed the characteristics of the overlying strata structure and the distribution law of lateral abutment pressure, revealing the plastic zone evolution mechanism and stress concentration effect of the pillar under the superimposed influence of residual stress from adjacent goafs. Based on the limit equilibrium theory, a calculation model for pillar width was established. Numerical simulation was used to analyze the stress distribution, plastic zone development, and deformation characteristics of pillars with different widths, determining that a reasonable pillar width of 20 m balances both stability and resource recovery efficiency. To address the issue of asymmetric large deformation in the surrounding rock of roadways with this pillar width, an integrated control technology was proposed, termed “basic bolt‐cable support + pillar‐side cable support + pillar‐side shoulder‐niche roof cable coupling reinforcement control technology.” This formed a roadway support scheme centered on high pre‐tension bolt‐cable support, with emphasis on reinforcing the goaf‐side wall and stress regulation. Field industrial trials demonstrated that after applying the reasonable pillar width and supporting control technology determined in this study, roadway surrounding rock deformation was significantly reduced, and stability was greatly improved. This successfully resolved the maintenance challenges of such roadways and notably enhanced the safety and efficiency of face mining. The research results provide a theoretical basis and technical reference for section pillar design and roadway maintenance under similar mining conditions.