深古河道区地铁车站基坑坑底隆起机理研究

Study on the Mechanism of the Base Heave during the Metro Station Excavation in Deep Paleochannel Area

摘要: 近年来的上海地铁建设中的案例表明，深古河道区的地铁车站基坑坑底隆起与常规地层条件下存在显著差异。本文采用水土耦合有限元研究了两种情况下深古河道区地铁车站坑底隆起特征，一种情况是土体无卸载回弹、只有塑性剪切变形；另外一种情况是考虑卸载造成的弹性回弹。根据计算结果，给出了土体塑性变形和弹性回弹对坑底隆起的贡献，指出基坑开挖过程中深古河道区土体向坑内的塑性流动是导致坑底隆起量较大的主要因素。

Abstract: Cases in the construction of subway Shanghai in recent years show that there is a significant difference between the base heave of metro station constructed in paleochannel area and that in conventional geological conditions. In this paper, the soil-water coupling finite element method is used to analyze the characteristics of base heave in the excavation of the subway station in paleochannel area under two conditions. One is no elastic swelling and only plastic shear deformation occurs in the soil; the other considers the elastic swelling due to the unloading. Based on the analysis results, the contribution of plastic deformation and elastic rebound to the base heave is given. It is pointed out that the plastic flow of soil toward the pit during the pit excavation in the paleochannel area is the dominant factor resulting in large base heave.