方形隧道稳定性极限分析有限元数值模拟

FE Numerical Simulation for Limit Analysis of Stability of Square Tunnel

在支护反力的作用下,隧道的应力边界条件发生较大变化,其稳定性分析亦变得十分复杂。为模拟这种复杂工况,采用极限分析有限单元法对方形隧道稳定性进行数值模拟分析。首先基于某些合理的计算假定,建立一种可以考虑多种因素影响的简化计算模型,在此基础上利用极限分析有限单元法求得不同影响因素下的隧道稳定系数;根据计算结果拟合出稳定系数的无量纲分析图表和经验计算公式,并基于各参数分析获得隧道破坏模式的变化规律,最后通过实际算例验证本文方法的可行性。研究表明:隧道稳定系数随H/B(埋深比)增大而减小,随φ(内摩擦角)和σt(支护反力)增大而增大;当φ较小时,H/B的变化对稳定系数产生显著的影响,而当φ较大时,H/B的变化对稳定系数影响甚微。

Under the change and the stabili action of supporting force, the stress boundary conditions of tunnel undergos great ty analysis becomes very complicated. In order to simulate this complex situation, finite element method in limit analysis is used to simulate the stability of a square tunnel. First, based on some reasonable calculation assumptions, a simplified calculation model which can consider multiple factors is established, and the stability coefficients of tunnel under influence of different factors are calculated by using the finite element method in limit analysis. According diagram and empirical equation for stability coefficients to the calculation result, the dimensionless analysis are fitted out, and the variation rules of tunnel failure mode are obtained through parametric analysis. Finally, the validity of this method is verified through actual examples. It shows that （1） tunnel stability coefficient decreases as H/B increasing, while it increases as internal friction angle φ and support reaction o1 increasing; （2） when φ is smallei, the change of H/B has a significant impact upon the stability coefficient, while the change of H/B has little effect upon the stability coefficient when φ is larger.