Failure analysis and innovative pressure load-off control technology of deep coal roadway both ribs: A case study

Abstract

Traditional borehole pressure load-off involves the direct creation of closely spaced boreholes on the target protection roadway ribs. This inevitably causes the dense borehole to pass through the anchoring structure of the roadway ribs, causing failure of the anchoring structure. Given this context, this study focuses on the return air main roadway (RAMR) within the mining area, specifically, the target protection roadway. We conduct a comprehensive investigation into the failure mechanisms and control technologies of the deep coal roadway both ribs through on-site investigation and testing, numerical simulation, and engineering applications. The results obtained from this study are as follows: ① Considering the shortcomings of traditional borehole pressure load-off and the construction environment of the RAMR, this study proposes, based on the overall anchoring of the full anchor cable for the roof and rib of the target protection roadway, the construction of an upward crossing-stratum borehole at the floor belt main roadway (BMR) to excavate large pressure load-off holes (LPLH) in the stress peak band (SPD) far from the anchoring structure of both ribs of the target protection roadway. ② This method avoids directly drilling boreholes in the shallow anchoring structure on both ribs of the target protection roadway; meanwhile, the coal slag generated during the construction of the LPLH is discharged into the belt conveyor through small boreholes in the rock layer at a certain inclination angle. This approach ensures that high stress is transferred to the roadway rib deep part without compromising the integrity of the shallow anchoring structure. ③ Innovatively introducing deviatoric stress analysis indicators into the study of pressure load-off control of roadway surrounding rock. Numerical simulations were conducted to investigate the response characteristics of the deviatoric stress of the surrounding rock under different crossing-stratum borehole angles, row spacings, and LPLH diameters, and the optimal crossing-stratum borehole parameters were obtained. ④ An expandable and shrinkable water-storage bag system was designed to monitor the convergence of pressure load-off holes inside the roadway. Onsite engineering test results verified the effectiveness of this technology in controlling the surrounding rock a deep coal roadway.