Study on combined pressure relief and scour prevention technology of high-level roadway and crossheading

The instability of high hard roof after deep-buried and extra-thick coal seam mining causes the phenomenon of strong ground pressure to stand out, which seriously threatens mine safety production. In order to explore a new scheme of pressure relief and scour prevention, taking 8302 working face of Xinjulong Coal Mine as the research background, a scheme of pressure relief and scour prevention by combined blasting of high roadway and gateway was put forward. By combining theoretical analysis, physical simulation and numerical calculation, this paper analyzes the principle of cooperative pressure relief of high roadway blasting and gateway blasting, reveals the fracture instability mechanism of high roadway blasting pressure relief on hard roof, and clarifies the evolution characteristics of high roadway blasting on coal seam stress field. According to the field working conditions, the pressure relief and monitoring scheme of combined blasting of high roadway and gateway is designed and practiced, and remarkable pressure relief effect is obtained. The conclusions are as follows: ① The joint pressure relief of high roadway and gateway weakens the overlying strata structure, causing a large number of cracks, destroying its continuity and reducing the bearing capacity of overlying strata.② Blasting in high roadway reduces the initial caving step of high key strata from 144 m to 84 m, and the periodic caving step from 24−30 m to 12−24 m. The vertical stress of coal seam decreased from 18.1−18.3 MPa to 16.2−18.0 MPa, with the largest decrease of 11.47%, which improved the stress distribution of working face. ③ The pressure relief scheme of combined blasting along the gateway and high roadway in 8302 working face is designed. The monitoring scheme is made from the aspects of surface deformation, overlying rock stress and deep displacement of roof.④ The field engineering practice shows that the microseismic energy events of 104 J and above decreased by 64.3%, and the microseismic events gradually changed from “low frequency and high energy” before modification to “high frequency and low energy” after modification. After pressure relief by combined blasting, the deformation of surrounding rock, borehole stress and stress of anchor cable are highly sensitive to faults and irregular mined-out areas, but after entering the normal stage, the stability of surrounding rock is improved, and the pressure relief effect by combined blasting is remarkable. It provides theoretical basis and practical reference for solving the problem of strong ground pressure behavior caused by hard roof with large mining height.