Dynamic behaviour of pile foundations with soil-pile interaction

Pile foundations are often used in soft soils to support heavy structures, such as offshore towers, nuclear power plants, tall buildings, dams and bridges. There are many situations where these structures may undergo dynamic loading, for example, earthquake forces, wave forces, wind forces, blasting and unbalanced machines etc. There has been a remarkable increase in the study of pile dynamics in the last twenty years, although piles have been used for hundreds of years. -- In this study, the dynamic behavior of single piles and pile groups are investigated theoretically and compared with experimental results performed earlier. Both theoretical and experimental studies have shown that the dynamic response of the piles is very sensitive to the properties of the soil in the vicinity of the piles. The impedances of the soil layer are formulated for different modes of vibration based on a new model of the boundary zone with non-reflective interface, which is more realistic and robust than the current leading models of Novak and Veletsos. -- With the impedances of the soil media derived, the stiffness and damping for single piles and pile groups are presented. The validity of the boundary zone model for the soil-pile system is verified by comparison with the dynamic experiments which were conducted on single steel piles and on a concrete pile group in the field, respectively. The effects of non-linearity of the soil-pile system under strong excitation, the pile-soil-pile interaction (group effect) and the influence of frozen soil on the piles are investigated comprehensively. The results obtained from this study provide a guideline for engineering design, to increase the safety of the piles and the structures