Analysis of settlements caused by dewatering in Yishanlu metro station in Shanghai

With the development and utilization of urban underground space and rail transportation, more and more attention has been paid to the settlement caused by dewatering during construction of deep foundation pits. The settlement at Yishanlu Metro Station of Line 9 in Shanghai caused by dewatering is studied, based on the laboratory model tests, field monitoring and numerical simulation. The results show that (1) The relations between ground settlements and water level of dewatering well at different depths of diaphragm retaining walls are found according to the analysis of laboratory model tests. (2) Based on the settlement curves calculated by multipoint displacement meters, ‘bifurcation’ and ‘inconsistent’ of the settlement curves are obtained. That is to say, the downward expansion takes place in some soil layers, which causes great deformation in deep soil layer than in relatively shallow soil layer. It is the first time that the ‘reverse rebound’ phenomenon is discovered. (3) Numerical analysis software-MODFLOW is used to study the mechanism of “reverse rebound”.