Optimization and application of entry formation parameters by roof cutting pressure relief with dense boreholes in thin coal seams

To tackle the technical problem in the No.203 thin coal seam working face of Ruineng Coal Industry, where directional blasting roof cutting is prohibited due to explosive controls, this paper proposes and applies a self-formed entry technology based on roof cutting and pressure relief using dense boreholes. Through laboratory tests, borehole imaging, and numerical simulations, the structural characteristics of the working face roof were systematically analyzed. Based on a comparative analysis of 33 numerical simulation scenarios, the optimal combination of drilling parameters was determined: an inclination angle of 15°, a hole depth of 8 m, and a spacing of 200 mm. Utilizing these parameters, a collaborative reinforcement support scheme combining "long anchor cables in the roof + anchor cables in the ribs" was designed. Field tests demonstrate that this scheme successfully limits the maximum roof-to-floor convergence to 262 mm. The average periodic weighting step distance of the working face is 11.6 m, and the dynamic pressure influence zone extends approximately 100 m. The surrounding rock of the retained entry stabilizes after being affected by mining for 100 m, achieving a favorable entry retention outcome.