Large deformation control methods for roadways in thick coal seams with high mining height and hard roof

For the control of surrounding rock in thick coal seams with high mining heights and hard roofs, the traditional roadway layouts employing coal pillars often induce strong strata behavior, resulting in large deformations, rock bursts, and other destructive issues in surrounding rock. Based on excavation theory, an excavation compensation theory was introduced, and a support system coupling roof-cutting pressure relief with high pre-stressed energy absorption was constructed. Directional pre-splitting fractures were introduced to sever stress transmission between the roadway roof and goaf roof, thereby reducing accumulated elastic strain energy in the surrounding rock. NPR (Negative Poisson's Ratio) high prestressed anchor cables were developed to control surrounding rock deformation. When the load generated by the coal-rock mass exceeded a critical threshold, the supporting components absorbed the impact energy through deformation, mitigating energy accumulation. To meet the technical requirements of non-pillar mining with roof-cutting for pressure relief, two key techniques, namely directional roof-cutting and gangue roadway side support, were proposed. Field tests demonstrated significant pressure relief effects, with the maximum pressure-relief ratio on the cutting side reaching up to 19.5%. The surrounding rock deformation rate and magnitude were significantly reduced, with the maximum deformation limited to 52 mm, confirming superior strata control performance.