Study on key parameters of roof cutting and roadway protection under hard rock stratum in No.1 Coking Coal Mine

Taking the roof cutting and roadway protection project of 8311 fully mechanized mining face in No.1 Coking Coal Mine as the research object, the key parameters of pre-splitting blasting roof cutting under the condition of direct roof containing thick hard sandstone are studied. The dynamic model of double-hole blasting was constructed, and the continuous-discrete element coupling numerical simulation method was used to compare and study the influence of different roof cutting parameter combinations on the deformation law of roadway surrounding rock. The research shows that the roof cutting technology can shorten the length of the cantilever structure of the roadway roof and achieve the dual effects of stress release and roadway protection. The adjustment of roof cutting height parameter mainly controls the filling density of gangue in goaf and the thickness of cantilever rock beam, while the change of roof cutting angle dominates the length of cantilever structure and the lateral restraint effect of gangue on roof. Both of them have optimal threshold and nonlinear positive correlation. It is verified by engineering that when the roof cutting height is 8.5 m, the roof cutting angle is set to 25°, and the blasting hole spacing is adjusted to 750 mm, the stability of roadway surrounding rock is effectively controlled, and the technical goal of gob-side entry retaining is successfully realized.