Abstract: It is vital to foreknow the overall settlement of bridge foundation for high speed railway in order to keep control of the bridge line. However, it is questionable to calculate the overall settlement of the large caisson foundation at a great depth by using layer-wise summation method recommended in the specification. In this paper, a deep and large caisson foundation under main tower of a long span cable-stayed bridge is taken into account. The overall settlement of caisson foundation is calculated by finite element method (FEM) with Mohr-Coulomb model (M-C), hardening-soil model (HS) and small-strain hardening soil model (HSS), respectively. Compared with the field monitoring data, the numerical results show that the overall settlements with HSS model are in good agreement with the monitoring data. Furthermore, the settlements in the following construction stages are rationally predicted by FEM. For layer-wise summation method recommended in the specification, the empirical settlement coefficient is corrected based on the monitoring data, and it is found that when the empirical settlement coefficient is equal to 0.13, the settlements by summation method are consistent with the monitoring data in this case.

Key words: long span cable-stayed bridge, caisson foundation, foundation settlement, small-strain hardening soil model (HSS), layer-wise summation method