Zonal instability identification and full-sequence hierarchical control strategies for surrounding rock in composite-roof coal roadway

Composite roof coal roadways suffer from developed bedding planes, low cementation strength and delayed staged surrounding rock instability, and conventional one-step support methods poorly adapt to these complex geological conditions. Taking the 1211(1) transportation roadway of Guqiao Coal Mine as the engineering background, this study adopts full-section real-time bolt stress monitoring to explore the temporal and spatial distribution of support stress, identify critical instability zones, and develop a graded, phased differentiated surrounding rock control system with optimized excavation and construction schemes. The results reveal that bolt axial force experiences three evolutionary stages: rapid growth, decelerated growth and stable fluctuation. Surrounding rock stress and support bearing capacity show distinct spatial heterogeneity, with the bearing capacity ordered as central roof > upper rib > lateral roof > lower rib. The central roof and upper rib are high-risk instability zones with severe stress concentration and sensitive bolt stress response, while other zones maintain sufficient support redundancy and good rock stability. Based on the staged deformation and stress redistribution mechanism of surrounding rock, a full-cycle closed-loop control system integrating advance pre-control, early intensive support, transitional stabilization and late cable reinforcement is established. A zonal differentiated support strategy is formulated, implementing intensive reinforcement in key hazardous zones and conventional support in stable areas. Combined with delayed cable support technology, a three-dimensional coupled stress field of shallow bolts and deep cables is constructed, which effectively remedies the defects of traditional support, such as uncoordinated stress adaptation, insufficient deep support and late structural failure. Three phased support modes with matched temporal and spatial parameters are determined, and construction processes are optimized for efficient parallel operation. Field applications verify that the optimized scheme ensures reliable stability and safety of composite roof roadways. After implementation, the daily excavation circulation increases from 6 to 15 ~ 18 cycles, and the daily advance footage rises from 6.0 m to 15 ~ 18 m, significantly improving excavation safety and construction efficiency.