| With the increase of height of tall buildings in our country, the thickness of raft become larger and larger when raft foundation or pile-raft foundation is adopted. Owning to lack of research on properties of thick-raft foundation, the appropriate assigning principles and calculation methods are lacked in engineering field. Instead the traditional design methods that lack accuracy are used in designing thick-raft foundation. It usually results in too thick raft, and make the cost of foundation very high.In this paper, on the base of the interactive principles of superstructure, base and soil, Many factors are considered. The method corresponds to real foundation working conditions. By research done on a structural model with numerical calculation method. The effects of some factors, such as superstructure stiffness, thickness of raft, compressive modular constant of soil, suspended width of raft and raft concrete intensity, on the working behavior of thick-raft foundation are analyzed. And in coordination with data obtained from an engineering test on site, the regularities of foundation settlement and the distribution properties of pile reaction, soil reaction and steel stress in raft, of the pile-(thick)raft tested are analyzed. In the same time, the calculating results with finite element method almost correspond with measured results.The interaction of low-storied podiums with a high-rise building is studied through some simulation tests. Really, it is studied on the interaction of the frame structure,thick raft foundation, and soil. The deformation and reaction of the thick raft foundation can be measured. It is obtained from the simulation tests and numerical analysis. It is shown that the engineering characteristics of whole raft foundation are closely related with the span of low -storied podium nearby the high-rise building. A new conception of the effective range of interaction is proposed in this paper.
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