基于能量原理的大孤山露天矿西井边坡开挖稳定性动态调控

借助FLAC3D内嵌的FISH语言并基于边坡在开挖过程中的系统能量守恒原理,实现了对露天矿边坡模型在开挖扰动过程中的能量计算,定义了单元体能量损伤变量Du和系统能量损伤变量Ds,结合尖点突变理论并以系统总耗散能作为状态变量,构建了边坡系统的能量突变判据。以大孤山露天矿西井边坡为例,通过能量突变与损伤演化分析、安全系数变化分析、位移场演化分析以及施工成本比较分析,实现了不同治理方案情况下西井边坡开挖稳定性的动态调控并确定了最优治理设计方案。研究表明:能量突变特征值Δ<0是判定露天矿边坡在第ni步开挖后局部围岩系统失稳的充要条件;当西井边坡由-258 m平台开采至-294 m平台时,边坡稳定性受到开挖扰动影响较为严重;通过能量突变与损伤演化分析等上述4个方面分析的综合考虑,建议选用削坡15 m+巷道边坡加固+-210 m平台加固的方案作为西井边坡稳定性综合治理的初步设计方案;能量突变特征值和安全系数随开挖次数的变化趋势具有一致性,验证了利用提出的能量突变判据评价露天矿边坡在开挖过程中的稳定性是合理可行的,为西井边坡在后续开挖过程中局部岩体失稳防治提供了一定的理论参考。

Dynamic Monitoring of the Excavation Stability of Xijing Slope in Dagushan Open-pit Mine Based on Energy Principle

With the help of FISH language FLAC3Dembedded and based on the system energy conservation principle in the process of slope excavation,the energy calculation of open-pit slope model in the process of excavation disturbance was realized,and the element energy damage variable Duand system energy damage variable Dswere defined.Combined with the cusp catastrophe theory and taking the total dissipative energy of the system as the state variable,the energy catastrophe criterion of slope system was constructed.Taking the Xijing slope of Dagushan Open-pit Mine as an example,the dynamic monitoring of excavation stability of Xijing slope under different treatment schemes were realized and the optimal treatment design scheme was determined through the analysis of energy mutation and damage evolution,the change of safety factor,the evolution analysis of displacement field and the comparative analysis of construction cost. The results show that energy mutation eigenvalue Δ < 0 is a sufficient and necessary condition of the instability of local surrounding rock system after the ni-th excavation;the slope stability is seriously affected by the excavation disturbance when the Xijing slope is mined from the-258 m platform to the-294 m platform;it is suggested that the scheme of"cutting slope 15 m + roadway slope reinforcement +-210 m platform reinforcement"should be selected as the preliminary design scheme for the comprehensive treatment of west well slope stability through the comprehensive consideration of the above four aspects;the variation trend of energy mutation eigenvalue and safety factor with excavation times is consistent,which verifies that it is reasonable and feasible to use the proposed energy catastrophe criterion to evaluate the stability of open-pit slope in the process of excavation.The study provides a certain theoretical reference for the prevention and control of local rock mass instability in the follow-up excavation process of Xijing slope.