Mechanics analysis and repairment example of shaft collapse caused by the cross-border mining of nearby small coal mines

Based on the collapse of auxiliary shaft in a coal mine, the collapse mechanism and repairing scheme of shaft are analyzed.The results show that the main reason causing the collapse of the auxiliary shaft is cross-border exploitation of several nearby small coal mines.Combined with the perturbation analysis of cross-border exploitation, the mechanical model of shaft is established, and the force conditions under uniform and non-uniform ground stress are analyzed respectively.With the increase of the uneven lateral pressure coefficient β, the stress difference increases at different extreme value places of the shaft collapse, which affects the ultimate bearing capacity of the wellbore and is not conducive to the stability of the wellbore.Meanwhile, the process of damage of cross-border exploitation is reproduced by using FLAC-3D, the deformation and force condition of the shaft are studied under the condition of different protective coal pillars.When the protective coal pillar is less than 60 m, the deformation of the shaft is large.Under this condition, the shaft may lead to deformation and failure.Combined with the above research, the cement fly ash grout filling and the reconstruction of surrounding rock are put forward for repairing the collapse shaft.Through the monitoring and analysis of the shaft deformation, it is considered that the shaft has good stability after the implementation of the repairmen scheme.