软土地区超深基坑变形特性离心模型试验研究

以上海某挖深38m的超深基坑工程为背景,利用离心模型试验研究了两组类似工况下超深基坑的围护结构变形、土压力变化、地表沉降等性状,同时也探索了主要工程性状的内在联系,并与现场施工实测数据结果进行了比较验证。试验结果表明:两组类似工况下超深基坑的开挖性状近似,其中,围护结构变形随开挖的进行而加大,在开挖后期水平位移最大值不再增大,只是最大值点下移,最大值点基本位于开挖面附近;围护结构后侧的土压力的变化值较好地吻合围护结构自身的变形状态;地表位移呈沉槽状,槽底随开挖的进行而逐渐加深并外移,试验结果与实测数据吻合。

Centrifuge model tests on deformation of ultra-deep foundation pits in soft ground

The main performance of ultra-deep foundation pits,such as deformation of retaining structure,change of soil pressure and surface settlement of perimeter ground,is studied through centrifugal model tests.Two parallel excavation test cases are designed in the research:one is an exclusive foundation pit and the other is that with adjacent high rise buildings,both of which are 38 m-deep multi-strutted soft ground foundation pits of a restoration work of metro line No.4 in Shanghai.The main performance of the two foundation pits is summarized and discussed,and comparison between the tests and field monitoring data is conducted.The results show similar performance in the two foundation pits,in which the deformation of retaining structure accretes with the progress of excavation at the early stages and the maximum lateral displacement of the wall along the depth remains in a certain value at the later stages,while the location where the maximum displacement occurs goes down and falls roughly around the excavation surface.The change of earth pressure accords with the deformation of retaining structure and the profile of ground settlement is observed to be in trough-shape,where the bottom of the trough goes deeper and farther away from the wall in the process.The results of the centrifugal tests conform well to the field measurement.