Mechanism and Control of Deformation and Failure of Mining Roadway in Thick Coal Seams Under Close Range Goaf

Abstract

In response to the problems of asymmetric deformation and failure caused by the close range and thick coal seam fully mechanized caving roadway, as well as the difficulty in ensuring the control effect of the roadway surrounding rock. Through numerical simulation and on-site industrial experiments, combined with the geological conditions of a certain mine site, the stress environment and plastic zone evolution law of the 13401 return airway in the entire cycle of excavation and mining are explored, and asymmetric support parameters are proposed to maintain the stability of the roadway surrounding rock. The results show that: (1) the presence of residual coal pillars and goaf in the upper coal seam leads to changes in the direction and magnitude of the principal/deviatoric stress in the surrounding rock of the roadway, while the nonuniform stress distribution causes butterfly shaped failure in the plastic zone of the roadway surrounding rock during excavation and recovery stages; (2) the theoretical calculations show that the plastic zone is not sensitive to the increase of support resistance, and the effect of increasing the support resistance within a certain range on reducing the failure range of the roadway surrounding rock is limited, and the roadway surrounding rock support should be changed from deformation control to stability control. (3) Based on geological conditions, stress field distribution, and the failure mode and range of tunnel surrounding rock, an asymmetric support optimization scheme is proposed using anchor cables for combined support. On-site mine pressure observation data shows that the application effect of the support optimization scheme is good.