| Pile raft foundation has the good integrity, the high vertical bearing capacity, the small foundation settlement, strong ability to adjustment uneven subsidence, and more open internal spatial compared with the pile box foundation. Simultaneously it may rely on greatly level load caused by the wind load or the earthquake function and has strong ability to anti- overturn. At present pile raft foundation applied in the high heavy building or the building of soft soil area has become commonly used foundation form. Pile-soil-pile interaction influence scope is measured and the revision models on pile-soil-pile interaction influence coefficient of the theory of elasticity are obtained by a series of regression analysis, which is based on a series single pile, plate, single pile with cap, double piles with cap experiments and the monolithic pile raft foundation of principal building and podium model experiment of principal building adjusted foundation rigidity design for reducing different settlement in site. The malpractice of pile raft foundation tradition design method is elaborated, which is based on interaction principal of superstructure-foundation-subsoil and test results of subsidence and pressure of on the top of pile. The new idea of adjusted foundation rigidity design for reducing different settlement is suggested to both reduce the unequal settlement, and improvement pile raft foundation stress character. Finally, superstructure, foundation and subsoil (pile-soil) interaction is analyzed by simplification numerical analysis method based on revised pile-soil-pile interaction influence coefficient. The main works as follows:1. This paper pointed out that the theory solution of elasticity exaggerated the pile - pile, pile - soil, soil - soil interaction influence through the contrast between the result of large scale model tests, the test results in-situ and the theory of elasticity solution, which lead to the large subsidence predicted value and overestimate the head of pile reaction the non-uniformity (or raft bottom foundation earth pressure non-uniformity). Finally, the author pointed out that the difference between the theory solution of elasticity and the real value must be estimated at most, and the theory solution of elasticity must be revised through lots of the test results in-situ and model tests results. 2.This paper summarize the research actuality on the load proportion shared by cap and analyze single pile with cap and group pile foundation bearing capacity behavior in order to explain that there are differences between the bearing capacity behavior of single pile with cap and group pile foundation. Therefore, we cannot bring single pile with cap's bearing capacity test result simply into group pile foundation design calculation. The ultimate bearing capacity of single pile with cap is much larger than the sum of the ultimate bearing capacity of single pile and plate under the condition of small pile spacing. Under the condition of large pile spacing pile cap effect coefficient can't also reach to 1.0. The conclusion "1+1≧2" is obtained. But in composite group piles tests, foundation soil beneath the pile cap bearing capacity then greatly reduces. The conclusion that ultimate bearing capacity of composite pile foundation is smaller than the sum of ultimate bearing capacity of all single piles and plates is obtained. Finally, the conclusion that the load proportion shared by cap in-situ is much smaller than the proportion calculated by elasticity theory is obtained by contrast between group piles model tests results and elasticity theory calculation on the load proportion shared by cap.3.In this thesis the applied concept optimized design idea based on adjusted foundation rigidity of principal building, that is through changing the rigidity distribution of subsoil and foundation piles to mate with the load distribution, which results in minimizing differential settlement and interior force of foundation of high-rise buildings with frame-tube or frame-shear wall structures and tower-podium connected buildings. The concept design based on adjusted foundation rigidity has been verified through the large scale model tests in site. The editor introduced the optimization design process applying the idea in the end.4.Adjusted foundation rigidity design for reducing different settlement, post-pouring belt, measure of increasing settlement are not adopted in order to research change of settlement, load transferring, internal force of raft board and super-structure under the condition of the monolithic pile raft foundation of principal building and podium, which lead to relative unequal settlement to be bigger than the permissible value of standard slightly directly. The author specially carry on the discussion in order to reduce principal building and podium unequal settlement, which point out that principal building and podium foundation connecting design may consider to coordinate the two foundation settlement method, namely taking the pile raft foundation to reduce the high-level part subsidence. The independent foundation and standard shape foundation in the natural foundation may be used in the podium. When the ground water level is high, the anti-water board must be used between the cellular girder. In order to increase settlement the slag and benzene board may be layed under the beam-board raft foundation. Swelling and recompression based on structure excavation may cause the advantageous effect to reduce the unequal settlement. When the podium surpasses 4～5 layer the subsidence pouring belt may be not established under the condition of adopting increasing settlement measures. The model experiment is unable to simulate subsoil soil swelling and recompression effect that is caused by structure excavation, which also causes the unequal settlement slightly to be bigger than standard permissible value between the mail building and podium.5.Sub-structure law is applied to carry on the rigidity to condense of superstructure. At the same time medium thickness board theory and Mindlin-limited compression layer mixed revision model is adopted to simply calculate interaction of pile raft foundation. The uniformity of numerical analysis results and the model test results is good.
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