Effect of open-pit to underground mining on slope stability in Longshou Mine

Abstract：According to the practical state of rock mass movement,deformation and fracture induced by underground mining,a systematical GPS monitoring network was established on the ground surface of the mine.Based on persistent monitoring in the last five and half years,the results show that a large-scale subsidence trough has been developed after the transition from open pit mining to underground mining.Almost all coordinates of the monitoring points are being changed constantly.In the upper surface of the ore body,the maximum horizontal displacement reach up to 853.1 mm,and the maximum three-dimensional displacement reach up to 951.7 mm.While in the lower surface of the ore body,the maximum horizontal displacement reach up to 763.5 mm,and the maximum three-dimensional displacement reach up to 952.1 mm.Furthermore,at the bottom of the pit,the largest accumulated upheaval displacement reach up to 458.1 mm because of the dual effects of the extrusion of high-steep opencast slope and underground mining.In addition,a 3D numerical model was established to reveal the stress environment around the excavation and opencast slope rock mass,discussed the rock mass movement and deformation,stress distribution and failure mechanism.Then,combined with the monitoring results and field investigation,and pointed out that the overall stability is relatively good in current stage.