Mechanism of non-uniform expansion and stability control in surrounding rock failure zone due to superimposed mining

In order to reveal the deformation and failure characteristics of surrounding rock under the influence of superposed mining, comprehensive investigations including field monitoring, theoretical analysis & calculation, numerical simulation and field trial were carried out in 160206 working face of Yangchangwan Mine. The stress evolution field and the plastic zone distribution characteristics of surrounding rock in return airway under superimposed mining-induced stress field were studied, and the non-uniform expansion mechanism of coal roadway under superimposed mining was revealed. The results indicated that a high deviatoric stress environment of the return airway in front of the 160206 working face could be incurred by the superimposed mining effect of the upper and lower mining district suble-vels, which was the main controlling factor for the asymmetric failure of the return airway. The plastic zone of the roadway under superimposed effect expressed a butterfly-like pattern under the high deviatoric stress, and the butterfly leaf deflected to the goaf side. Non-uniform expansion characterized by expansive failure scope at the rib-side roof and pillar-side floor could be noticed in the plastic zone of the surrounding rock. Therefore, combined support technical consisting of coordinated strengthening support by asymmetric long and short cable bolts, advancing unitary chocks, and stress-relief boreholes was proposed. The industrial trail in a site impacted by the superimposed mining demonstrated favorable results. © 2024 China University of Mining and Technology. All rights reserved.