Mechanism and control of pillar bidirectional reinforcement during pre-cut roof gob-side entry driving in gently inclined coal seams

Addressing the challenge of coal pillar stability control in gob-side entries of gently inclined coal seams, this study utilizes the 7134 working face of a specific mine as an engineering case. By integrating theoretical analysis, numerical simulation, physical similarity modeling, and field monitoring, the research comprehensively investigates the mechanism of pre-cutting pressure relief technology and bilateral reinforcement of coal pillars, along with their impact on the stability of surrounding rock in roadways. The study reveals the critical role of cutting parameters in blocking stress transfer from the overlying strata of the goaf to the roadway, identifying the optimal pre-cutting scheme (18 m height, 90° angle) that effectively eliminates the influence of main roof rotation and squeezing on the coal pillar. Innovatively, the core mechanism concerning the relative positioning of the anchored sections within the bilateral support structures of the coal pillar is elucidated: when the support bodies create overlapping zones within the pillar, a "tension-anchoring effect" is generated. This effect significantly improves the internal stress distribution, effectively constrains the bulking deformation of the coal pillar, and inhibits crack development, thereby substantially enhancing the overall stability and load-bearing capacity of the narrow coal pillar. Building upon this mechanism, the research also proposes a novel design method for determining the length of anchor cables on the ribs of narrow coal pillars, identifies key design parameters, and validates the reliability of this method through similarity simulation and field engineering practice. Field application demonstrates that employing a combined support system with high pre-stressed bolts and cables effectively controls roadway surrounding rock deformation, significantly improving safety and stability throughout the service life of the roadway. This research provides a theoretical foundation and an effective technical approach for controlling surrounding rock stability in gob-side entries of gently inclined coal seams.