Research on Deformation and Failure Character of Underground Surrounding Rock and Overlying Strata Transition from Open-Pit to Underground Mining

Based on the engineering background of Jingning phosphate mine of Yunnan Phosphate Chemical Group Co. LTD. the deformation and failure character and dynamical evolution process of underground surrounding rock and overlying strata were studied after transformation from open-pit to underground mining. And the similar material simulating experiment and digital photographic measurement technology were used to investigate these issues, with the conditions oftwentydegreesore body dips and fifty degreesore body dips. The experimental results showed: The results showed that: ①The evolution process of mining deformation of underground surrounding rock and overlying strata could be divided into three stages, which contained small deformation in originally small and local scale stage, linear continuously increasing stage and the whole nonlinear violent collapsing stage;②With the ore body dip increasing from twenty degrees to fifty degrees, the mining affecting area narrowed down in a small range, the deformation slowed down of underground surrounding rock and overlying strata;③The abrupt  instability of  underground surrounding rock during the process of ore pillar recovery, and it presented the obvious “The Domino Effect”. The relevant conclusions provide theoretical reference for ground pressure management and slope maintenance in a mine transition from open-pit to underground mining.