Study On The Long-Short-Pile Composite Foundation Of Design Theory

The long-short-pile composite foundation as one of many new types of composite foundation is gotten the more and more attentions of geotechnical engineers, because of its economy. 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 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. The general developing situation and basic theory of composite foundation are summarized in this paper, the creation of the long-short pile composite foundation; study the operating characteristic of the different piles and the research production in long-short pile composite foundation is specially introduced.2 Study the bearing capacity and settlement design theory of the long-short-pile foundation and its the model and methods of bearing capacity and settlement have been proposed, amend safety factor of bearing capacity calculation, and generalize scope of application of the long-short-pile foundation. An engineering case is analyzed, the theoretical calculation results are compared with the monitor in site, the close results are showed to testify the applicability of the long-short-pile composite foundation, and have important engineering value in further analysis and application to the long-short-pile composite foundation.3 The paper also shows the advantage and disadvantage of method based on bearing capacity controlled design and method based on settlement controlled design from optimum design for foundation. And also generalize the design method and step of long-short-pile foundation based on settlement controlled design, and shows the formula that estimate the length of pile rationally. Finally, the design of the practice based on the control of settlement principle shows that long-short-pile foundation has good technical and economic results and it can keep the project safely.