特殊类型基坑变形性状二维有限元分析

Two-dimensional finite element analysis of deformation characteristics of some special deep excavations

不同开挖宽度与深度比条件下基坑围护结构与周围土体的变形特性将发生变化。采用二维有限元方法分析了不同开挖宽度与深度比(L/D)条件下无支撑悬臂开挖基坑的变形性状,详细探讨了开挖宽度与深度比对地表沉降、地表水平位移、坑底隆起、坑底水平位移及围护结构侧向变形的影响。计算结果表明:在基坑开挖深度不变的条件下,地表沉降量、坑底隆起量及坑底水平位移量均随L/D的增加呈非线性增长,开始增长迅速,当L/D达一定值后,数值几乎不再变化;地表水平位移量随L/D的增加先减小后增大;围护结构侧向变形随L/D的增加逐步由顶端内倾型过渡到整体向坑内移动的顶端外倾型。L/D越大,围护结构的整体侧向位移越大。

The excavation width of some deep foundations and underground structures ranges from several to hundreds of meters in engineering. The deformation characteristics of the retaining structures and ground of these deep excavations vary with the excavation width. The two-dimensional finite element method is adopted to investigate the deformation characteristics of retaining structures and ground with different ratio of the excavation depth to the excavation width. The numerical results show that the magnitude of ground settlement and basal heave as well as the magnitude of horizontal displacement of basal all increase nonlinearly with the ratio. The magnitude of horizontal ground surface displacement decreases with the ratio first,then increases. The lateral deformation of the retaining structure varies gradually from introversion-type to extroversion-type as well as overall movement towards the inside excavation with the increase in the ratio.