龙首矿露天转地下开采对边坡岩体稳定性的影响

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

针对甘肃金川龙首矿露天转地下开采条件下的边坡岩体变形、破坏和稳定性问题,在矿区大范围内建立了地表岩移GPS监测网络。持续5.5 a的监测结果表明:地下开采已经引起地表大范围的岩体移动和变形。矿体上盘地表监测点累积最大水平位移量达853.1 mm,最大三维位移量达951.7 mm;矿体下盘地表监测点累积最大水平位移量达763.5 mm,累积最大三维位移量达952.1 mm。同时受深凹露天边坡的挤压和地下开采双重影响,坑底隆起区地表监测点累积最大隆起量达458.1 mm。在此基础上,通过相应的三维数值模拟,研究了露天边坡地下开采采场围岩和边坡的力学环境,探讨了围岩移动变形、应力场分布和破坏机理。综合已有的现场监测结果和实际勘察情况,认为目前露天边坡整体稳定状况相对良好。

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.