邻近地铁深大基坑开挖变形与控制措施研究

Study on deformation characteristics and control measures of deep and large foundation pit excavation neighboring metro

以邻近运营地铁隧道的福州正祥广场深大基坑为实例,结合基坑开挖过程中围护结构侧向位移、周围土体沉降和地铁隧道水平及竖直位移的现场实测数据,系统分析了不同施工阶段基坑围护结构、周边土体以及地铁隧道的变形特性,讨论了采用围护结构刚度优化、支撑体系优化以及开挖工序优化等变形控制措施的合理性。结果表明:基坑淤泥层开挖所引发的侧向位移约占总侧向位移的50%~60%;受开挖方式和支护方式的影响,基坑东侧(邻近地铁隧道)与西侧围护结构的最大侧移位移平均值分别为0.128%H和0.228%H(H为基坑开挖深度),最大侧向位移所在深度约为0.25H~H;地铁隧道的位移曲线与基坑周围土层、围护结构的位移曲线的发展趋势具有良好的一致性,均表现出显著的空间效应。

Taking the deep and large foundation pit of Fuzhou Zhengxiang Square adjacent to the operating subway tunnel as an example, combined with the on-site measured data of the lateral displacement of the enclosure structure, the surrounding soil settlement and the horizontal and vertical displacement of the subway tunnel during the excavation process of the foundation pit, a systematic analysis was carried out on the deformation characteristics of the foundation pit envelope, surrounding soil and subway tunnels in different construction stages, and the rationality of the deformation control measures such as the optimization of the envelope structure stiffness, the optimization of the support system and the optimization of the excavation process were discussed. The results show that the lateral displacement caused by the excavation of the silt layer of the foundation pit accounts for about 50%~60% of the total lateral displacement. The average maximum lateral displacement of the side enclosure structure is 0.128%H and 0.228%H respectively, which influenced by the excavation method and support method.(H is the excavation depth of the foundation pit), and the depth of the maximum lateral displacement is about 0.25H~H. The displacement curve of the subway tunnel has a good consistency with the development trend of the displacement curve of the soil layer around the foundation pit and the envelope structure, and both show significant spatial effects.