Abstract
To address the challenge of instability control in the collaborative bearing structure of stope roof and barrier pillars in short-wall interval filling mining, a combined approach of theoretical analysis, numerical simulation, and field application was adopted. A mechanical model of the roof-pillars collaborative bearing structure was established, and the analytical solutions of roof bending stress were derived. The effects of mining mechanics and structural parameters on the stability of the roof-pillars structure were further analyzed, and the optimal branch roadway width, number of barrier pillars, and elastic modulus of the backfilling body were determined. The results were validated through numerical simulation and field testing. The results indicate that: ① The analytical solution of the roof deflection equation shows significant variation in the maximum bending stress distribution along the branch roadway roof, with the peak stress occurring at the branch roadway roof, which is identified as the most vulnerable area for roof instability. ② Orthogonal tests and variance analysis reveal that the elastic modulus of barrier pillars exerts the most significant influence on roof stability (variance 120.3), followed by branch roadway width (56.5) and the interval number of barrier pillars (19.8). The optimized parameter combination includes a branch roadway width of 5 m, two barrier pillars (10 m in width), and a backfilling body with an elastic modulus of 1.2 GPa. Under these conditions, the mean maximum roof bending stress is 14.8 MPa, with a range of 22.4 MPa, achieving both mechanical equilibrium and economic efficiency. ③ Numerical simulations show that during three mining cycles, the stress distribution of barrier pillars gradually transitions from a "double-peak" to a "single-peak" pattern. The maximum vertical stress increases from 15 MPa to 24.65 MPa; however, the barrier pillars remain stable, the development of the surrounding rock plastic zone is controllable, and the roof deformation (163.5 mm) is within the safety threshold. ④ In industrial applications, field measurements at the 2-106 filling working face show that the maximum deformation of the roof and floor is 54 mm, and roof separation is less than 24 mm, thereby validating the effectiveness of the optimized parameters. This study reveals the collaborative bearing mechanism of the roof-pillars system under the condition of two unfilled branch roadways, proposes optimization criteria for structural parameters, and provides theoretical support and engineering reference for the safe application of short-wall interval filling mining technology.