铁古坑采区地下开采对露天最终边帮稳定性影响分析

舞阳铁矿铁古坑采区由露天开采转入地下开采，地下开采的不同阶段会对已有露天最终边帮的稳定性产生不同影响，若无法有效判断露天最终边帮的失稳工况，将对地下开采的安全生产造成威胁。选取典型勘探线剖面，建立二维有限元数值模型，按开采顺序分露天开采结束、-160 m阶段、-220 m阶段、-280 m阶段、-340 m阶段、 -400 m阶段开采完成共6个工况，运用有限元局部强度折减法计算露天最终边帮顶、底帮的安全系数，分析地下开采对露天最终边帮稳定性的影响。结果表明：有限元局部强度折减法可以通过1个数值模型分别计算出顶、底帮的安全系数；随着地下开采深度的增加，露天最终边帮顶帮安全系数逐渐降低，在地下开采至-220 m阶段时顶帮处于极限稳定状态，开采至-280 m阶段及以下阶段时顶帮发生破坏；地下开采对露天最终边帮底帮安全系数影响较小，整个开采过程中底帮一直处于稳定状态。

Influence of Underground Mining on Final Slope Stability of Open Pit at Tiegukeng Mining Area

Tiegukeng mining area of Wuyang Iron Mine is transiting from open pit to underground mining. The under-ground mining in different stages will have a different influence on the final slope stability of open pit. It will threaten the pro-duction safety of underground mining if the unstable working condition of the final slope can not be judged. Two-dimensional fi-nite element numerical model is built by selecting the typical exploratory line profiles. Six working stages was finished with the order of the open pit,-160 m stage,-220 m stage,-280 m stage,-340 m stage and -400 m stage. The safety factors of the hanging wall and the footwall of the final slope are calculated with the local strength reduction method of finite element to ana-lyze the impact of underground mining on stability of the final slope. The results show that:the local strength reduction method with finite element can be used to calculate the safety factors of the hanging wall and the footwall through the numerical simula-tion. With the underground mining depth increase,both safety factors above decreases gradually. The slope will be kept in ulti-mately stable condition at the -220 m stage and the hanging wall collapses at the-280 m stage or below. Underground mining has a little impact on the safety factor of the final slope footwall,so the footwall is always kept in stable.