露天转地下开采引起露天采场边坡垮塌数值模拟研究

Numerical Simulation of Open Pit Slope Collapse Caused by Transition from Open Pit to Underground Mining

以某金属矿山露天转地下开采引起露天采场边坡垮塌为研究背景,采用三维数值模拟研究方法展现了矿体开采过程中围岩塑性区发展过程,并分析了围岩塑性区分布的变化规律。结果表明:(1)空区上部岩层主要以拉伸破坏模式为主,其他部位岩层主要以剪切破坏为主,西部边坡坡面的一侧已经与地下采空区塑性区相互贯通。(2)东部矿体采用充填法开采,一定程度上控制了地表塌陷;产生塑性区的部位为西部边坡和靠近西部边坡的露天采场底部。(3)开采前期西部矿体在西部边坡坡面和露天采场底部产生的塑性区较多;开采后续水平矿体对地表塑性区的产生影响不大。(4)模拟矿体开采过程,可将产生的塑性区划分为3个阶段,有2个突变点:第1个阶段对应西部边坡开始出现裂缝、局部垮塌滑坡;第2阶段对应边坡出现较大范围垮塌滑坡、露天采场底部出现裂缝、西部边坡脚出现塌陷孔洞;第3阶段塑性区占比逐渐增加。研究成果可为矿山滑坡治理和矿山安全生产提供参考。

For studying the open-pit slope collapse in a metal mine caused by transition from open-pit to underground mining, a 3 D numerical simulation method was used to analyze the progress of plastic zone in the surrounding rock of ore body, and the law of variation for the plastic zone distribution in the surrounding rock.(1) Tensile failure is the main cause of failure in the strata above the goaf, while the other parts of strata are predominated by shear failure, and the plastic zone of the underground goaf extends to one side of the western slope of the open pit.(2) The eastern ore body is mined by cut-and-fill, which controls the surface subsidence to some extent, and plastic zone occurs in the western slope and the bottom of open pit near the western slope.(3) At the early stage of mining of western ore body, there are more plastic zones occurring in the western slope and the bottom of open pit, and the subsequent mining of horizontal ore body has little impact on the plastic zone of the ground surface.(4) The progress of plastic zones can be divided into three stages with two abrupt change points: at the first stage, cracks start to occur on the western slope, and collapse and landslide occur in some parts;at the second stage, a large scale of collapse and landslide occur on the slope, and cracks occurs at the bottom of the open pit, and void collapse also occurs at the toe of the western slope;at the third stage, the proportion of plastic zones increases gradually. The research results can provide reference for safety in mine production.