A novel asymmetric stress unloading technology in two sides of coal roadway in deep mine: A case study

Abstract

The existing stress unloading technology using dense equal-diameter large drilling usually results in damaging the load-bearing structure of the shallow surrounding rock of the roadway. Therefore, this study, while providing full anchor cable strong anchorage support for the roadway sides, proposes an asymmetric stress unloading technology on the two sides of a coal roadway. Small-diameter holes are directly drilled in the shallow low-stress area, and the large-diameter stress unloading hole (LSUH) is excavated in the deep stress concentration peak area for the right side of the roadway; utilizing the floor rock roadway, by drilling upward through the rock stratum, excavating the LSUH in the deep stress concentration peak area for the left side of the roadway. Full anchor cable reinforcement technology for the shallow surrounding rock of roadway sides forms a thick layer anchorage load-bearing structure, avoiding cracks further development of the shallow coal seam of the roadway side and creating a quality stress environment for the implementation of the LSUH in the deep area of the roadway side. The small drilling and the coal slag discharge of the roadway left side does not pass through the shallow anchorage area of the roadway left side, and the shallow small drilling on the roadway right side is supported reinforcement by the steel pipe, which minimize the impact of hole-manufacturing on the shallow anchorage area to the greatest extent possible. Large-diameter weak structural stress unloading holes are arranged in the deep stress concentration peak area of far away from anchorage area of the roadway side, making the high concentration stress areas around the roadway be transferred to deeper area without affect the stability of the shallow anchorage area, also making the plastic deformation of the surrounding rock in the stress concentration area of the roadway side be transferred to the weak structural area of the stress unloading holes. A numerical model for the asymmetric stress unloading technology on the two sides of a coal roadway is established to investigate the influence of different stress unloading parameters on the roadway side stress. Engineering practice shows that this technology can ensure the long-term stability of the roadway.