The deformation mechanism and control of the crushed stone slope in the roadway formed by cutting roof in big mining height hard roof

Aiming at the problem of large deformation of the crushed stone slope support in the roadway formed by cutting roof under the condition of thick coal seams and hard roof,the collapse characteristics of the three stages of deformation and collapse impact of the crushed stone slope,crushed stone bearing,and compaction stability were analyzed through mechanical calculation and theoretical analysis,and the influencing factors were determined. Then,a combined control system for the crushed stone slope of “ combined blasting + retractable U-beam + steel mesh + gangway rockbolt + unit bracket + hydraulic prop” was proposed. The optimization measures were simulated by 3DEC,and it was found that the stress and displacement of the crushed stone slope were reduced to different degrees. The joint control optimization scheme was applied in the field. The actual measurement shows that the lateral pressure of the optimized crushed stone slope is reduced by 18. 6%. The peak pressure is reduced by 24. 6%. The overhang distance after the rack is reduced by 42. 1%. It effectively weakens the impact of rubble collapsing in the goaf,and the effect of pressure relief is obvious.