Study on Overburden Stability Control by Expandable Pillar Support for Multi-stope Mining in a Gently Inclined Thin Orebody

To solve the problems of high ore resources loss and natural pillar splitting failure in multi-stope mining of gently inclined thin orebody by traditional room-and-pillar method, the overburden stability control technology by replacing natural pillars with pre-stressed expandable pillars (PEP) is developed in this paper. By means of numerical simulation and physical experimental methods, the distribution characteristics of stress, displacement, and failure zone of surrounding rock in multi-stope mining with and without PEP support were studied. The results demonstrate that the PEP supporting effect can improve the stress environment of surrounding rock compared with the unsupported condition, divide the stress reduction zone of the stope roof, and avoid the overburden failure induced by tensile stress penetration in the shallow-buried stope. Moreover, the PEP support can effectively limit the crack propagation depth and damage degree of the surrounding rock. Deriving from the physical test, compared to the unsupported scenario, the vertical deformation of the stope roof is reduced by about 44% on average with the PEP support, thus preventing overburden collapse caused by large deformation. Besides, the greater the mining depth of the stope, the greater the increase in the bearing capacity of the PEP support. Field industrial test shows that the stope and PEP supports are visually safe and stable after mining. The overburden stability control technology with PEP support proposed in this study can offer a key reference for improving ore resource recovery in multi-stope mining of gently inclined orebody.