Deformation and damage characteristics of surrounding rock and zonal support countermeasures for a dynamic pressure roadway in deep back-mining

Abstract

The deep rock mass has long been subjected to a complex geomechanical environment of “three highs and one disturbance,” rendering the structural characteristics and mechanical behavior of deep rock masses more complex. The −850 m roadway in Qujiang Coal Mine is longitudinally tiled under the 805 working face and coal pillar. Affected by the mining of the upper working face and the bias of the coal pillar, the roadway presents various deformation and damage characteristics. The deformation and damage patterns of the dynamic pressure roadway of the back mining are analysed through field investigation, bolt and anchor cable force monitoring, and peripheral rock deformation monitoring, and the proposed support countermeasures are verified and analysed by using FLAC3D numerical software. The results show that: (1) Using bolt/anchor cable axial force monitoring and surrounding rock deformation monitoring, it is found that the mining-induced dynamic pressure −850 m roadway displays distinct zonal damage characteristics, which can be divided into a rear sustained (high-pressure) deformation zone and a forward disturbance (dynamic-pressure) deformation zone. (2) In the forward disturbance (dynamic-pressure) deformation zone, damage mainly occurs in the upper roof of the roadway, predominantly as sliding shear damage; in the rear sustained (high-pressure) deformation zone, damage mainly occurs at the floor and the arch foot. The floor is prone to plastic extrusion deformation and damage, while the arch foot mainly experiences punching shear and internal folding damage. (3) According to the different damage modes of the −850 m roadway, it is proposed to implement “three-anchor” combined support technology in the rear sustained (high-pressure) deformation zone, and to implement “resistance-yielding combined” support in the forward disturbance (dynamic-pressure) deformation zone. (4) FLAC3D numerical simulation results are consistent with the field monitoring data, confirming the rationality and effectiveness of the proposed zonal support measures. The research results provide a certain reference for surrounding rock deformation control in deep mining dynamic pressure roadways in the future.