| During the analysis and designing of the piled raft foundation, one may always find that there exist two or more bearing strata in soil. The bearing capacity of the shot pile foundation that bearing on the lower bearing strata is enough while the amount of settlement is too big, especially when there is soft clay below the bearing strata. Too many long piles are needed when the long pile foundation that bearing on the deeper bearing strata is chosen, it makes the construction difficulty and engineering investment increased, the bearing capacity of the lower bearing strata cannot be well used at the same time.Considering the case that there two bearing strata in soil and low settlement of foundation is wanted, based on the controlling settlement principle, the design philosophy of long-shot pile foundation is presented. The long pile is to control the settlement and short pile to provide bearing capacity. The long pile's capacity of controlling settlement and the bearing capacity of the lower bearing strata are fully utilized.The long-shot pile foundation is a new type of foundation. There are too many problems that are not researched, and the design theory and calculation method haven't come into being. Therefore, in order to spread the application and develop the technology of this new type of foundation, it's necessary to make a systemic research on its behavior. In this paper, a systemic research was made with finite element method, model experimentation and analytical method etc. The discussion of the design theory was also made based on the analysis and calculation. The studies of the paper consist of the following parts:(1) Presented the design philosophy of long-shot pile foundation, based on the controlling settlement principle and the traditional pile foundation design philosophy. Long pile is manly to control the settlement, and the short pile is manly to provide bearing capacity.(2) Analyzed the working performance of the long-short pile foundation whit the...
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