Study On Settlement Calculation And Time Effect Of Pile Foundation Considering Pile-Soil Relative Displacement

Pile foundations are usually used in practice, because of its high bearing capacity and its ability to control the settlement and reduce non uniform settlement, so the research about the settlement calculation is very significant in pile foundation design. The settlement calculation about piles is very complicated due to the interactions among the piles, the caps and surrounding soils, and the nonlinear behavior of the soils. The existing methods to calculate the settlement of piles usually considered the pile shaft and the pile end, respectively. As the sea-crossing bridges and high-rise buildings increasing, the super-long piles and long-short compound piles are widely used in practice. But the corresponding researches are backward in actual project, and the researches about pile foundations are also faced with new topics. In this paper, the analytical and semi-analytical researches about piles are present. The main work and innovative achievements are as follows:1. The Boxluscal function is present to simulate the pile shaft resistance and the corresponding relative displacement. The relationship between the pile end resistance and pile end settlement is also described using the function.2. Considering the relative displacement and the nonlinear behavior between pile shaft and surrounding soils, the calculation method about pile settlement in homogeneous soils is obtained. As the pile end settlement increased, the rigidity of the surrounding soils and pile end soils varied using the Boxluscal functions, and then disseminated in layered soils.3. Considering the nonlinear deformation of pile shaft concrete, the approach to calculate the settlement of super-long piles is obtained, and the behavior of the super-long piles is analyzed. The results show that the settlement of super-long piles is mainly due to the nonlinear deformation of the pile shaft. The effective length of super-long piles is discussed considering the nonlinearity between the pile shaft and surrounding soils, and the factors that affect the effective length of super-long piles are also analyzed.4. Based on the FEM software ABAQUS, the interactions between piles with different lengths are analyzed, considering the different space between piles and the difference in pile length. Based on the methods to revise the interaction factors proposed by Wong and Poulos, the interaction factors between piles with different lengths are revised. The interaction factors between pile bases are calculated by the displacement solution obtained by Mindlin, and then used to calculate the settlement of the long-short compound piles. The results obtained by the proposed method are well consist with that from ABAQUS.5. Considering the change of pile bearing capacity with times and the existing researches, the method to calculate the pile bearing capacity changed with time is obtained.6. The settlement calculation of pile foundations with time is proposed in this thesis, and the factors that affect the calculation are analyzed. The rationality of the proposed method is validated by the present data.7. Considering the time-effect in pile bearing capacity, a practical engineering is analyzed by the proposed methods to calculate the settlements of long-short compound piles.At the last part of this thesis, the main work is summarized and the future researches are recommended.