上海软土地区地铁车站深基坑的变形特性

通过对上海软土地区地铁车站基坑实测数据的分析，探讨了基坑围护结构变形、坑外土体变形及地表沉降的一般规律.结果表明：上海软土地区地铁车站基坑围护结构的最大侧向位移为开挖深度的0.04%～0.6%，平均值为0.3%；围护结构侧向变形通常为深层凸鼓形，围护结构最大侧移点深度一般位于开挖面以上1.5 m至开挖面以下7 m；基坑周边最大地表沉降为开挖深度的0.05%～0.7%，为围护结构最大侧向变形的0.4～1.0；采用钻孔灌注桩结合高压旋喷桩止水帷幕的地铁车站基坑的变形控制通常优于地下连续墙和SMW工法.

Deformation Characteristics of Deep Excavations for Metro Stations in Shanghai Soft Soil Deposits

The case histories of deformations due to the deep excavations for some metro stations in Shanghai soft soil deposits were presented and discussed.The statistics show that the ratio of the maximum lateral displacement of the retaining structures to the excavation depth ranges from 0.04% to 0.6%,and the mean value is about 0.3%.The deformation of the retaining structures develops a clearly deep-bulging profile as the excavations continue,and the maximum lateral displacement of the retaining structures usually appears between 1.5 m above the excavation surface and 7 m below the excavation surface.The ratio of the maximum surface ground settlement to the excavation depth lies between the range 0.05% to 0.7%,and the ratio of the maximum surface ground settlement to the maximum lateral displacement of retaining structures falls within the range 0.4 to 1.The construction method of cast-in-place piles combined with compaction grouting for cutting off groundwater is generally proved to be more effective in controlling deformation of deep excavations than diaphragm wall or SMW method.