上海软土条形市政深基坑变形性状的实测研究

对一个挖深17.5 m的多道支撑上海软土条形市政深基坑的变形进行实测分析,研究发现其围护墙侧向位移沿深度方向呈典型弓形分布，并存在一定踢脚变形，对在影响范围内“坑中坑”，深坑对浅坑围护墙侧向位移影响明显，在设计上增加匝道外侧围护插入比以及在匝道外侧围护与深坑第一道围檩之间设置混凝土传力带，可有效减小匝道外侧开挖变形；同时抗隆起安全系数与最大侧移关系之值处于经典的统计范围之内，围护墙最大侧移与挖深之比值基本介于0.30%～0.77%，处于二、三级变形控制线之间；墙后地表沉降分布曲线与上海基坑标准预测曲线更为契合，其与墙体侧移比值基本介于0.4～2.0，其均值为0.80，无匝道区域平均值相对偏大；立柱桩回弹具有明显的空间反应特征，基坑中间位置的回弹量约为均值的1.3~1.45倍和基坑边侧立柱桩回弹量的2倍，空间反应特征较为明显。

Field Study on Deformation Character of Strip Municipal Deep Foundation Pit in Soft Soil of Shanghai

A field analysis is carried out on the deformation of a multi-supported strip municipal deep foundation pit with 17.5 m depth in Shanghai. It shows that the lateral displacement of its retaining wall is distributed in a typical bow shape along the depth and there is a certain kick deformation, which has a significant impact on the lateral retaining wall displacement of shallow pit in the affected range of "pit in pit". In design, the insertion ratio of the outer ramp retaining wall can be increased, and a concrete transmission belt can be set between the outer retaining wall of ramp and the first retaining purlin of deep pit, which can effectively reduce the outer excavation deformation of ramp. At the same time, The value of the relationship between the anti-hump safety factor and the maximum lateral displacement is within the classical statistical range. The ratio of the maximum lateral displacement to excavation depth of the retaining wall is basically between 0.30%~0.77%, which is between the second-level and third-level environmental protection control lines. The distribution curve of surface settlement behind the wall is more in line with the standard prediction curve of foundation pit in Shanghai. Its ratio to wall lateral displacement is basically between 0.4 and 2.0, and its average value is 0.80. The average value with no-ramp region is relatively large. The rebound of column piles has the obvious spatial response characteristics. The rebound amount in the middle of the foundation pit is about 1.3~1.45 times of the average value and 2 times of the rebound amount of column piles on the side of the foundation pit. The spatial response characteristics are more obvious.