地铁荷载作用下软土地基长期沉降的有限元分析

为讨论地铁荷载作用下上海软土地基的长期沉降问题，本文利用边界面本构模型结合弹塑性动力固结有限元理论，通过ABAQUS数值软件分别建立了轨道-隧道-土体相互作用模型，考察单孔和平行双孔两种隧道布置情形。分析了单次、多次地铁列车动荷载加载引起的隧道地基沉降规律，并结合3种经验模型预测了隧道的长期沉降，得到3种不同加载工况下由列车动荷载引起的动应力幅值与沉降；并对比分析了单双孔隧道的沉降特性，将模型计算结果与沉降实测值进行比较。结果表明，采用模型的预测值与沉降实测值接近；双孔隧道的土体沉降不仅是单孔隧道沉降值的简单线性叠加，而且存在一定程度的增大。

FEM ANALYSIS OF LONG-TERM SETTLEMENT OF SOFT SOIL CAUSED BY METRO LOADING

To investigate the subway induced long-term settlement of soft soils in Shanghai, a bounding surface constitutive model combined with the theory of elastoplastic dynamic consolidation is employed in this finite element analysis using ABAQUS software. A three dimensional track-tunnel-soil interaction model is established; and two kinds of tunnel layout are covered, that is single tunnel and double-tube parallel tunnel, respectively. The settlement regulations of subway tunnel under single and multiple train loads are studied. On this basis, three empirical calculation methods are applied to estimate the long-term settlement of the subgrade, the amplitude of dynamic stress and settlement caused by moving trainload under three different loading conditions are obtained as well. In addition, the settlement characteristics of single and double tube tunnels are compared, and the numerical solution is also compared with the measured values. The analysis shows that, the calculated result is consistent with the field test result. The subgrade settlement of the double tube tunnel is not merely a linear superstition of two single tube tunnel, amplification existed.