Located at Jiefangqiao Station of line 3 in Tianjin Metro, the Class I foundation pit is 13. 1 m deep and the Class II foundation pit is 31. 5 m deep. The outline of the foundation pit is irregular and polygonal. There are several external corners between the two classes. Underground diaphragm wall is used as the retaining structure with two rows of reinforcement concrete supports for the Class I foundation pit and four ( or five partly) rows of steel tube supports for the Class II foundation pit. To ensure the safety of the excavation, the Three-Dimensional Finite Element Method (3D FEM)is used to simulate the whole construction process of the foundation pit, including the construction of retaining structure, excavation of foundation pit and the installation of the supports. Then the change of internal force of the retaining structures and the supports during the construction process are analyzed. Comparing the result of 3D FEM with the monitoring data, the result of 3D FEM is regarded as reliable one.%天津地铁3号线解放桥站,1级基坑深度13.1m,2级基坑深度31.5m,外形呈不规则多边形状,1,2级基坑间存在多个阳角.围护结构采用地下连续墙,1级基坑采用2道钢筋混凝土支撑,2级基坑采用4道(局部5道)钢管支撑,为保证车站基坑开挖安全,采用三维有限元模拟基坑施工全过程,通过模拟围护结构施工、基坑开挖及支撑架设全过程,分析施工过程中围护结构及支撑的内力变化,最后对计算结果进行分析,并与施工完成的结果比较,表明采用有限元模拟基坑开挖过程的计算结果是可靠的.
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