Analysis on Stability of Top Pillar When Coming into Underground Mining from Open-Pit

Based on the site-specific conditions,the physico-mechanical properties and structural features of rock and mining conditions,the 3-D numerical analysis softwares MSC.PATRAN and MSC.NASTRAN were first used to model wholly the Shirengou Iron Mine.Readjusting repeatedly the parameters of the models,the 9 proposed schemes were simulated and analyzed individually and compared with each other.It was concluded that the 9th scheme can make the top pillar stable,and an optional mining program and some measures were proposed in detail to control effectively the spalling and caving of rock mass.It also provided a reliable analytic method and scientific evidence for choosing reasonable dimension of top pillar when coming into underground mining from open-pit.