露井联采逆倾边坡稳定性数值模拟

Simulated study on the stability of countertilt slope in the combined open-pit and underground mining condition

为最大限度回收资源,倾斜矿体开发时常采用露天与井工联合开采方式,形成露井联采逆倾边坡,由于受到双重采动效应影响,其变形破坏机理及稳定性问题变得极为复杂,是采矿工程领域研究的难题之一。以平庄西露天矿顶帮边坡为研究对象,同时考虑拉伸和剪切两种破坏判据,应用RFPA强度折减法对露井联采逆倾边坡岩移规律及稳定性进行了数值模拟。通过对比分析单一露天开采和露井联采条件下边坡岩体变形破坏规律、位移演化规律及应力分布特征的差异,揭示了地下开采对露天矿逆倾边坡岩移规律及稳定性的影响和原因。结果表明:单一露天开采时边坡发生滑移型破坏,而露井联采条件下边坡发生滑移-塌陷复合型破坏;受两种采动效应叠加的影响,地下采空区上方岩体以下沉为主,同时上山一侧岩体向露天采空区方向发生明显位移;受地下采动影响时,逆倾边坡稳定性下降,其根本原因是坡体内剪应力的大范围叠加升高,造成上部一定范围的岩体在边坡发生滑移前就遭到破坏,从而加剧了滑坡的发展。

This paper is aimed at numerical simulation on the stability of counter-tilt slope under the combined surface and underground mining condition by taking Pingzhuang Western Mine as a case study sample. As is known,the complex mode of open-pit mining and undersurface mining has usually been adopted to recover the coal sources to the maximum limit. However,since the deforming and failure mechanism dependent on this way of mining,it is often extremely complicated and controversial to organize the said combined mining mode so as to ensure the stability and the safety of the counter-tilt slope,for it is necessary to take into simultaneous account both the tension and shear failure criteria.In this paper,we have taken the top slope in the Pingzhuang Western Mine as our case study sample. In proceeding with our research,we have done a numerical simulation to examine the migrating rule and the stability of counter-tilt slope under the combined surface and underground mining with the RFPA strength reduction method,and then gained such maps as the displacement isolate-line,the displacement vector,the acoustic emission（AE）characteristics and the shear stress of the slope rock masses in case all kinds of mining methods were adopted for the study. The comparative analysis we have done in hoping to disclose the deformation and destruction regularity,the displacement evolution and the stress distribution regularity either under the simple or under the combined mining conditions,in addition to the impact of such displacements and evolutions on the slope movement regularity and the stability of underground mining context. The results of our simulation demonstrate that the simple surface mining is prone to the slipping failure whereas the combined mining subsiding is prone to the slipping-subsiding combined failure. For under the influence of the two mining effects,the rock masses over the mining area is likely to subside first and then to move upward to the surface with the obvious side-rise roadway. Therefore,the counter-tilt slope stability tends to decline under the combined mining condition in comparison with the combined mining one for the root reason that the superimposition of the shearing stress tends to increase in a wide range in the slope,which may lead to the destruction of part of the rock masses above the potential sliding surface to certain degree before the landslide. And,unfortunately,the destruction of part of the rock masses may naturally weaken the rock masses strength and aggravate the development of landslides. That is to say, the weakening of the rock mass strength should be taken as an immediate factor leading to the seismic failure.