Abstract: A simplified nonlinear approach for analyzing flexible piled raft foundation in non-homogeneous cohesive soil under excavation is proposed to investigate the influence of excavation on the bearing capacity of the foundation. The flexible piled raft is modeled as a thin plate through the finite element discretization. With the impact of soil excavation around the pile into consideration, the flexibility coefficient of pile top in non-homogeneous cohesive soil under excavation is obtained by employing the load transfer method; based on solutions for the stress and displacement in layered elastic half space, the interactions of the pile group-soil system are taken into account to determine the flexibility matrix of the pile group-soil system in non-homogeneous cohesive soil under excavation. By integrating finite element method and finite difference method, the simplified nonlinear analysis method is obtained. Comparison between calculated results and test and theoretical results verified the validity of the present method. With the influence of soil excavation ignored, the load sharing ratio of soil in piled raft foundation will be underestimated, and the non-uniformity of load distribution at the top of foundation pile at the bottom of raft will be larger in the analysis results. The research results offer a basis for balance design for variable-rigidity of group piled foundation and piled raft foundation under excavation.

Key words: piled raft foundations, nonlinear analysis, unloading rebound of soil, non-homogeneous foundation, pit excavation