Optimized positioning and cross-layer control for roadways beneath residual coal pillars in extremely close-distance coal seams

In extremely close-distance coal seam (ECDCS) mining, section coal pillars remain after upper coal seam (UCS) extraction. Thus, for layout and support design of lower coal seam (LCS) mining roadways, it is critical to account for UCS goaf deterioration and residual coal pillar (RCP)-induced stress disturbance. Taking the 6.4 m layer spacing of ECDCS mining in Nanyangpo Coal Mine as a case study, this research aimed to determine the optimal layout and surrounding rock control method for the 24202-ventilation roadway in the RCP area. First, the challenges of roadway layout and support under RCP were clarified: three layout methods face distinct RCP-induced stress disturbances and goaf-related roof damage. A finite element model was established; the second invariant of deviatoric stress (J₂) and horizontal stress index were introduced to analyze plastic zone and stress evolution after UCS mining. Results show that J₂ distributes symmetrically, with its peak diffusing downward and attenuating in a “/\”-shaped pattern. Six schemes were simulated to compare plastic zone distributions at different positions, revealing that the optimal layout consists of a roadway alignment with the RCP center. Based on roadway layout and roof conditions, a cooperative control scheme was proposed: deep, strong anchorage with long cables across the RCP, and shallow stable support with short bolts in the ECDCS. This scheme secures roof cables anchored to the UCS RCP roof to achieve cross-seam anchorage. On-site borehole peeping and loose circle tests confirm smooth surrounding rock hole walls and limited failure range. Specifically, surrounding rock deformation and roof separation were controlled within 200 mm and 80 mm, respectively, with stable bolt/cable support resistance. These results offer an innovative solution for roadway layout design and support strategies under RCP in ECDCS, with significant engineering application value.