露天矿反倾边坡破坏模式及加固机制模型试验

Model test on failure mode and reinforcement mechanism of anti-dip slope in open-pit mine

为研究露天矿层状反倾边坡出现的大规模弯曲倾倒破坏模式,开展在未支护及恒阻大变形锚索(NPR锚索)支护条件下的45°倾角多节理反倾边坡开挖物理模型试验.采用多源监测系统采集边坡开挖过程中锚索轴力、应变场及位移场等数据.结果表明:无支护反倾层状边坡开挖过程中表现出4种典型破坏模式:后缘带张拉破坏、坡肩叠瓦状破坏、坡腰弯折破坏以及坡底冲切破坏;采用NPR锚索支护后的边坡在相同的开挖条件下未发生大面积失稳破坏;边坡开挖过程中,NPR锚索轴力呈突增、突降及稳定波动3种模式循环演变,分别对应边坡变形过程中单元板裂缝发育、断裂及坡体复稳3种现象;NPR锚索具有吸能特性,且锚索轴力预警准则同样适用于NPR锚索支护下的岩质反倾边坡.

In order to study the large-scale bending and toppling failure of layered anti-dip slope of an open pit mine, a physical model test of 45° inclination multi-joint anti-dip slope excavation under the condition of unsupported and NPR anchor cable support was carried out. A multi-source monitoring system was applied to gather the data during the excavation of slope such as the axial force of anchor cable, strain field and displacement field. The results show that there are four typical failure modes during the excavation process of an unsupported slope, which are tensile failure of trailing edge, imbricate failure of slope shoulder, bending failure of slope waist and punching failure of slope bottom respectively. The slope supported by NPR anchor cable does not cause large-scale instability damage under the other same excavation condition. During the excavation process, the axial force of NPR anchor cable has three modes of cyclic evolution: sudden increase, sudden drop and stable fluctuation, which correspond to the three phenomena of crack development of unit plate, fracture and slope stabilization respectively during slope deformation. The NPR anchor cable has energy-absorbing characteristics, and the axial force warning criterion of anchor cable can be applied to the rock anti-dip slope supported by NPR anchor cable.