露天矿烧变岩高边坡卸荷机理与稳定性研究

Study on unloading mechanism and stability of high rock slope in burnt rock open-pit mine

烧变岩裂隙发育、富水性强,严重威胁露天矿山采剥安全生产及其边坡稳定。为确定露天矿烧变岩高边坡隔水煤岩柱宽度,以新疆昌吉某露天矿北帮烧变岩高边坡为研究对象,通过构建坡体开挖卸荷的驼峰分布力学模型,将坡体卸荷松弛区域划分为拉裂区和压剪区两部分,分析了边坡后缘拉裂区裂隙的最大扩展深度;以卸荷松弛带宽度表征塑性剪切滑动面位置,推导了弹塑性条件下边坡浅表部破碎带与卸荷松弛带宽度的理论计算公式,进而确定了塑性滑动面位置及形态。结果表明:边坡后缘裂隙临界扩展深度随边坡倾角的增大而增大;卸荷松弛带宽度随岩石强度参数的增大而减小,随岩层埋深的增大而增大;北帮边坡后缘裂隙临界扩展深度为9.42 m,火烧区水位线处卸荷松弛带宽度为6.94 m;坡体潜在滑面安全系数均大于设计评价标准值;确定了北帮烧变岩高边坡的隔水煤岩柱留设安全宽度为36 m,为该矿的安全高效生产提供了技术保障。

The development of fissures in water-rich burnt rock pose a serious threat to the safe production and slope stability of open-pit mines.In order to determine the width of the water resistant coal rock column on the high slope of the burnt rock in open-pit mines,the northern slope of a certain open-pit mine in Changji,Xinjiang was taken as a research object.By constructing a mechanical model of a hump distribution for excavation and unloading of the slope,the unloading and relaxation area of the slope was divided into two parts:the tensile crack zone and the compressive shear zone.The maximum depth of crack propagation in the tensile crack zone at the rear edge of the slope was analyzed.And width of the unloading relaxation zone was used to characterize the position of the plastic shear sliding surface,with a theoretical calculation formula for the width of the shallow surface fracture zone and unloading relaxation zone of the slope under elastic-plastic conditions derived.And the position and shape of the plastic sliding surface are determined.The results indicate that the critical depth of crack propagation at the rear edge of the slope increases with the increase of slope inclination angle.The width of the unloading relaxation zone decreases with the increase of rock strength parameters and increases with the increase of rock burial depth.The critical depth of crack propagation at the rear edge of the northern slope is 9.42 m,and the width of the unloading relaxation zone at the water level line in the burning area is 6.94 m.The safety factors of the potential sliding surface of the slope are all greater than the design evaluation standard values.The safe width of the waterproof coal rock pillar on the high slope of the northern burnt rock has been determined to be 36 m.The research could provide technical support for the safe and efficient production of the mine.