Abstract: Research of settlement and load transfer law on the composite foundation is a very important content in the composite foundation theory; then it isn’t maturity to this kind of composite foundation studying of settlement and load transfer law on theory. In this paper, based on the vertical deformation model[1] and the radial deformation model[2], the control differential equations of pile and pile-surrounding soil are established by the elastic theory and the pile-soil displacement coordination condition. The analytical formulas calculating deformation of pile and pile-surrounding soil in the pile group composite foundation reinforcing area are derived under flexible foundation; at the same time the analytical formulas calculating the pile side shear stress and the vertical stress of pile and pile-surrounding soil are drew. For verifying feasibility of the method , the results acquired by this kind of method are contrast with the finite element method by way of calculating example. And also carrying on the model experiment. All results indicate: this kind of method has enough precision to analyzing load transfer law and deformation of the pile group composite foundation in reinforcing area under flexible foundation , it is simple to calculate, and is easy to engineering application.

Key words: composite foundation, settlement, load transfer, displacement coordination