Undrained seismic stability of dual unsupported circular tunnels was investigated in this work using a self-developed code for adaptive finite element limit analysis. The so-called pseudo-static method was used to simulate the seismic effects during an earthquake. Accurate upper and lower bounds of seismic stability factor [Formula: see text] were obtained by using an adaptive remeshing technique incorporated in the code. Comprehensive parametric studies of the problem variables, including the horizontal seismic coefficient [Formula: see text], the relative spacing ratio [Formula: see text]/[Formula: see text], the relative depth ratio [Formula: see text]/[Formula: see text] and the strength ratio [Formula: see text]/[Formula: see text] were performed to provide dimensionless design tables for practical uses. In addition, visualized results from AFELA were summarized to reveal how the failure mechanism of dual tunnels would evolve with varying problems variables. Numerical results showed that both the stability and failure mechanism of dual tunnels can be much affected by seismic effects which should be carefully considered for a reasonable design in earthquake zones.

中文翻译：

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双无支护圆形隧道超载荷载不排水抗震稳定性

在这项工作中，使用自主开发的自适应有限元极限分析程序研究了双无支撑圆形隧道的不排水抗震稳定性。所谓的拟静力法是用来模拟地震过程中的地震效应。通过使用包含在代码中的自适应网格重新划分技术，获得了准确的地震稳定性因子上限和下限[公式：见正文]。问题变量的综合参数化研究，包括水平地震系数[公式：见文]、相对间距比[公式：见文]/[公式：见文]、相对深度比[公式：见文]/[公式：见文]和强度比[公式：见文]/[公式：见文]提供无量纲设计表供实际使用。此外，总结了来自 AFELA 的可视化结果，以揭示双隧道的失效机制如何随着不同的问题变量而演变。数值结果表明，双隧道的稳定性和破坏机制都会受到地震效应的很大影响，在地震带进行合理设计时应仔细考虑。