Deformation control of large and deep foundation pit of Shanghai Expo axis by use of top-down construction method

Aiming at the deep and large foundation pit of Shanghai Expo axis and the complex underground project’s No.1 tendering section by use of the top-down construction method,the deformation rules of underground diaphragm walls under three different longitudinal excavation widths of the remaining berm and with or without inclined bracing setting are compared through centrifuge model tests.The effect of the inclined bracing on the enclosure deformation control is studied by numerical analysis considering the time-space effect.Results show that the longitudinal excavation width of the remaining berm at the middle plate has a great effect on the deformation of underground diaphragm walls,but that at the base plate has a less effect.It is thought that the middle plate and the inclined bracing have a large contribution to the deformation control of underground diaphragm walls.According to the environmental protection grade of the foundation pit,the inclined bracing is proposed to be set on the east side,and considered to be unnecessary on the west side.