Research on technology and application of hydraulic staged fracturing roof cutting and retaining roadway in hard roof

Aiming at the problem of controlling the surrounding rock of gob-side entry retaining caused by the difficult collapse of the hard roof of the coal seam, taking the 111 working face of a mine as the engineering background, the hydraulic staged fracturing roof cutting pressure relief is carried out on the roof of the retaining roadway. Firstly, a theoretical mechanical model is established to calculate and analyze the influencing factors of the hard roof collapse; then, the influence of different segmentation point spacing and borehole inclination angle on the roof cutting effect is compared by numerical simulation; finally, the hydraulic staged fracturing test is carried out on the spot and the effect is verified by the cross point method. The results show that the dip angle of the hydraulic staged fracturing borehole and the stress state of the staged fracturing point determine whether the roof can collapse in time, so the numerical simulation analysis is carried out, and the roof weakening effect is better when the spacing of the staged fracturing points is 3 m and the inclination angle of the roof cutting borehole is 45°. The maximum deformation of the roadway bottom in the field test is 210 mm, and the maximum amount of roof subsidence is 121 mm. The maximum approach of the two gangs is 42 mm and 61 mm respectively. This technology avoids the impact of the hard roof of the working face in gob-side entry retaining engineering, effectively solves the problem of surrounding rock control and provides a reference for solving similar problems in gob-side entry retaining engineering.