Numerical modelling of strata movement at footwall induced by underground mining

During metal mining, the deformation and failure of rock mass are very important factors that dominate rock movement and zoning. Numerical modelling provides a feasible way to study the deformation and failure of rock mass. In this study, a numerical method of UDEC was adopted to study strata movement mechanism influenced by NWW-trending joints at the footwall at Chengchao Iron Mine, and the Mohr-Coulomb model and the Coulomb-slip model with residual strength were adopted as the constitutive models of rock masses and joints, respectively. The whole strata movement process was simulated and the strata movement mechanism at footwall and zoning phenomenon was clarified. In the chimney caving development stage, gravity is the driving force and surface deformations are mainly subsidence deformation of the surface above the ore body. In the post-chimney deformation stage, horizontal tectonic stress is the driving force and surface deformation and subsidence are dominated by horizontal deformation of the hanging wall and footwall in the mining area. After the level −395.0 m is mined out, the deformation characteristics of deep surrounding rock were revealed by means of numerical modelling, the maximum failure depth of the cantilever beam and the spatial distribution of deep surrounding rock zones can be determined. At last, the influencing boundary of surface deformation expands rapidly in a linear way with the excavation step and the expanding velocity of the horizontal deformation is greater than that of the subsidence in the post-chimney deformation stage.