Stress Reconstruction and Expansion Strengthening via Unilateral Directional Roof Cutting for Roadway-Surface Synergistic Protection

Traditional caving mining methods in shallow coal seams often lead to roadway instability and ground subsidence, posing significant challenges to sustainable coal extraction. To address these issues, this study proposes an innovative mining technique based on unilateral directional roof cutting (UDRC) and investigates its geomechanical mechanisms through integrated numerical–analytical modeling and physical experiments. Taking the 44,203 working face of the Hongliulin coal mine as a case study, a modified cantilever beam mechanical model is first developed to characterize the stress redistribution caused by UDRC. This model explicitly links roof fracturing patterns with the optimization of stress transmission paths. A combined approach integrating physical model experiments and UDEC-based numerical simulations is then used to investigate the dynamic evolution of roof failure, gangue bulking characteristics, and stress transfer mechanisms. Results demonstrate that UDRC technology reduces vertical stress concentration in coal ribs by 22.2% through targeted directional fracturing, while enhancing gangue expansion coefficients from 1.21 to 1.40, achieving 93% gob compaction efficiency. The convergence of both roadway ribs decreased by 33.02%, the roof-floor convergence decreased by 46.69%, and surface subsidence by 81.6% compared to conventional methods. Field validations confirm that the proposed dual-path control framework—combining stress field reconstruction with the self-organized dilatancy of fragmented strata—provides a reliable numerical and analytical basis for optimizing shallow coal seam mining. This work advances geo-mechanical modeling by integrating waste utilization mechanics with stress-path design, offering a transformative approach to eco-efficient underground resource extraction.