Optimization Study on the Layout of Mining Roadways in the Lower Working Face of Ultraclose Coal Seams

China boasts abundant reserves of close-distance coal seams, where mining operations face complex stress environments and roadway stability. The work took the simultaneous mining faces of ultraclose coal seams in the Huayuan Coal Industry of Lingshi, Shanxi Province, China, as the research subject. Theoretical analysis and numerical simulation were used to investigate the stress distribution patterns under simultaneous mining in ultraclose coal seams and the rational coal pillar width for the lower working face. First, based on the related mechanical model, a theoretical solution for the coal pillar width was derived under limit equilibrium. Furthermore, a discrete element numerical model was established to simulate the stress evolution and surrounding rock failure characteristics under the disturbance of the double-side goaf in the upper seam and the single-side goaf in the lower seam. Multisource disturbances led to stress peak superposition, easily forming a stress concentration zone at the center of the lower pillar. This posed a severe threat to the stability of the surrounding rocks in the lower roadway. An 8-m pillar width provided the optimal balance between resource recovery and roadway stability, based on the stress, displacement, and plastic zone distribution observed across different pillar widths. Finally, in terms of stress redistribution, the roadway support parameters were optimized and applied on-site, with a favorable support effect achieved. The research findings provide theoretical foundations and engineering guidance for the layout and support design of lower roadways in ultraclose coal seam groups.