上海深厚软土层地铁车站基坑的侧向变形特征

Lateral Deformation Characteristics of a Subway Station Excavation in Deep Soft Clay in Shanghai

摘要: 本文详细介绍和分析了上海软粘土厚度较大(四十多米)的深古河道地区某地铁车站(开挖深度17.6 m)基坑地下连续墙侧向位移的特征、规律以及机理。结果表明：地下连续墙最大侧向位移与开挖深度的比值在0.17%至0.46%之间，开挖至12 m以后位移明显加大，超过报警值(0.4%)，出现“踢脚”的迹象；最大侧向位移与开挖深度的比值要远小于国外基于太沙基坑底隆起安全系数的经验关系。另外，与设计对比表明，设计给出的连续墙的侧向位移偏小，这可能与软土的侧向基床系数的选取有关。该工程案例表明深厚软土地区的地铁车站基坑的侧向变形较大，而与设计计算和理论分析的结果差异较大，因此应该重视对深厚软土层地铁车站基坑围护结构侧向变形的设计计算方法以及设计参数(如侧向基床系数)的研究，以提高设计计算的可靠性。

Abstract: The characteristics, laws and mechanism of the lateral displacement of the underground continuous wall of a subway station of (excavation depth of 17.6 m) in a deep paleochannel area with a relatively large thickness of soft clay (up to 40 m) in Shanghai are introduced. The ratio of the maximum lateral displacement of the diaphragm wall to the excavation depth is 0.17% to 0.46%. Between the excavation and the excavation to 12 m, the displacement increased significantly, ex-ceeding the alarm value (0.4%), showing signs of kicking. The ratio of the maximum lateral dis-placement to the excavation depth is much smaller than the empirical correlation based on the Terzaghi’s safety factor of base heave. In addition, the comparison with the design results shows that the lateral displacement of the diaphragm wall given by the design is smaller, which may be related to the selection of the lateral bed coefficient of soft soil. The project case shows that the lateral deformation of the foundation pit of the metro station in the deep soft soil area is large, but the results from the design calculation and theoretical analysis are quite different. Therefore, the lateral direction of the foundation pit of the deep soft soil layer metro station should be emphasized to improve the reliability of design parameters’ (such as lateral bed coefficients) calculations.