Instability Evolution Mechanism and Cooperative Control of Three-Soft Coal-Seam Roadway Surrounding Rock Subjected to Mining Disturbance

Using the No. 1513 return air roadway at Anyang Coal Mine as an engineering case, this study examines the instability mechanism and support control of three-soft coal-seam roadways. An integrated approach combining theoretical derivation, physical similarity modeling, and FLAC3D simulation was adopted to analyze fracture propagation, deformation characteristics, and support optimization of roadway surrounding rock containing weak interlayers under mining-induced disturbance. The results indicate that the weak interlayer in the immediate roof disrupts load transfer among roof strata and promotes roof separation and fracture development. Calculations based on composite beam theory show that effective anchorage reduces roof separation displacement by approximately 74%. Therefore, bolts and cables should be arranged to constrain the weak layer within the effective anchorage range and improve roof stability. The physical model reveals that fractures evolve progressively under mining-induced stress, following a three-stage process: local initiation in the ribs, deep extension toward the roadway shoulders, and roof–shoulder–rib separation coalescence. FLAC3D results further show that secondary mining intensifies roadway deformation. The maximum roof subsidence, rib convergence, and roof plastic-zone height reach 532 mm, 1100.5 mm, and 5.5 m, respectively. The deep roof, roadway shoulders, and middle rib sections are therefore identified as the primary reinforcement zones. On this basis, a coordinated roof–shoulder–rib support system was proposed by increasing roof-cable density, adding rib cables, and increasing bolt density in the roof and ribs. After optimization, roof-to-floor convergence and rib deformation were effectively controlled. The results provide guidance for surrounding-rock stability control and support-parameter optimization in three-soft coal-seam roadways.