基坑开挖与邻近地铁结构变形相关性的实测分析?

探究开挖卸载下基坑与近邻"上浮型"地铁结构的变形机制,以天津某邻近既有地铁的基坑开挖为例,通过实测手段分析基坑多期开挖条件下既有地铁结构的变形特点。基于基坑围护结构竖向变形,考虑基坑与地铁的水平相对位置L和开挖时间t,定义表示基坑围护结构竖向变形与地铁结构竖向变形相互关系的关联系数R,并对邻近地铁结构的竖向变形进行拟合与预测。探究三维空间下基坑与地铁水平变形的关系。研究结果表明:地铁结构整体表现为上浮,开挖期间累计竖向位移与累计水平位移的比值在0.5～1.5变化;基坑围护结构竖向位移乘以系数1000R/L可很好地拟合邻近地铁的竖向位移,关联系数R在基坑开挖过程中变化不大;三维空间下地铁结构纵向水平变形呈正态分布,与近地铁侧基坑围护结构同深度处的水平变形趋势一致。

Monitoring Data Analysis on Deformation Correlation between Foundation Pit and Adjacent Metro Structure

Study aims at deformation mechanism of foundation pit and adjacent "upward floating" metro structure under excavation and unloading. Taking a foundation pit near the metro tunnel in Tianjin as an example, the deformation characteristics of the metro structure under multi-stage excavation of foundation pit are analyzed through measurement. Based on the vertical displacement of foundation pit retaining structure, considering the relative horizontal position of foundation pit and metro L and excavation time t, defining the correlation coefficient R that represents the vertical deformation relationship between retaining structure of foundation pit and adjacent metro structure, the vertical displacement of the adjacent metro is fitted and predicted. The relationship between horizontal deformation of foundation pit and that of the adjacent metro structure under three-dimensional space was also studied. The results show that the adjacent metro structure is all uplifted, and the ratio of cumulative vertical displacement to cumulative horizontal displacement varies from 0.5 to 1.5 during the pit excavation. The vertical displacement of pit retaining structure multiplied by coefficient 1000R/L can well fit the vertical displacement of the adjacent metro, and the correlation coefficient R has little change during excavation. It was also found that the horizontal displacement curve of the metro structure was observed in a normal distribution, which is consistent with the horizontal deformation trend of retaining structure with the same depth. The method and conclusion can provide a reference for the design and optimization of similar projects.