The prediction of northern slope deformation and failure caused by the transformation of open-pit to underground mining in the Yanqianshan iron mine

The Yanqianshan iron mine is preparing to transform from an open-pit mine to an underground mine. We adopt the non-pillar sublevel caving approach to exploit the particularly thick steep ore bodies within the range from -183 m to -500 m from top to bottom. According to the features of ore body distribution and the approaches of exploitation, we expect that underground mining will result in the loss of stability on the northern slope of the open pit, causing traction-type landslides. Moreover, along with increasing the depth of the mining operation, the range of slope failure will continue to expand and further affect the safety of drainage features and roads distributed on the north side of the open pit. For this purpose, we select four sections along the trending direction of ore bodies and apply the limit equilibrium method to predict the failure process and characteristics on the northern slope according to the stratified mining process.