Parametric study of a new pressure relief borehole layout for high-stress roadway rockburst prevention

To address the challenge of coordinating "pressure relief" and "support" in the control of rock bursts in high-stress roadways, this study proposes a novel method of pressure relief using long-distance large-diameter boreholes arranged parallel to the roadway (LDBP), elucidates its underlying rockburst control mechanism. Theoretical analysis is conducted to propose the borehole arrangement and principles for determining the optimal parameters of LDBP. Through numerical simulations, the advantages of LDBP in achieving "pressure relief-support balance" are validated. The influence of borehole parameters on the roadway stress and energy evolution is studied. The results show that, compared with conventional borehole schemes, LDBP reduces stress and energy concentration in the roadway shoulder and sidewall regions while exerting only a minor effect on the overall roadway strength. As boreholes are positioned farther from the roadway, the peak abutment stress shifts deeper into the coal mass and decreases accordingly. The optimal location for LDBP is the interface between the plastic and elastic zones, which in practice in situ can be identified reliably using the drilling-cuttings method. Coordinated design of borehole spacing and diameter is essential for effective destressing; forming a continuous plastic zone is ideal, whereas improperly selected parameters may induce a "double-peak" stress distribution between boreholes and increase peak stress.