LAUSR

Abstract The 110 mining method, an emerging and innovative nonpillar longwall mining method, can dramatically increase coal recovery rates and reduce entry accidents. One of the core techniques of this method is roof splitting, the operation that is directly related to the stability of the retained entry. In this work, a directional roof split blasting (DRSB) technique was introduced, and the effects of DRSB on the stability of the entry surroundings were comprehensively studied at the meso- and macrolevels. First, a micromechanical damage model considering the heterogeneity of the roof rock was developed using the finite element method (FEM), and the blasting-induced damage evolution in the roof rock was numerically explored using the FEM model. Subsequently, the macroeffects of DRSB were studied using the finite difference method (FDM). A meticulously validated FDM numerical model incorporating a double-yield model for the gob materials and calibrated parameters was developed to investigate the effects of roof splitting on the stabilities of the entry surroundings. The numerical simulation results were finally verified using on-site monitoring data. These results indicate that the DRSB technique could effectively control crack propagation in the roof rock and protect the entry roof from being fragmented or damaged. Macroscopic analysis revealed that applications of DRSB affected the stress distributions and failure states of the entry surroundings. As the roof splitting effects were enhanced, more vertical stresses were transferred to the gob area, causing the stress concentrations in the entry surroundings to be mitigated. Consequently, the deformations in the entry surroundings were reduced, and the stability of the retained entry was improved. The proposed models and obtained results potentially produce reasonable values for the applications of pillarless mining in similar projects.