Scour effects on the dynamic lateral response of composite caisson-piles foundations considering stress history of sand

Abstract

Scour effect have a significant impact on the dynamic lateral response of composite caisson-piles foundations (CCPFs) because of the removal of soils around the foundation and the change of stress history of remaining soil. Based on the simplified method with the dynamic Winkler model, a computational method for predicting the dynamic impedance of CCPFs influenced by scour is developed. Subsequently, theoretical results for the response of CCPFs are verified by the 3D finite element method with sponge boundary. Finally, results from a case study show that scour has a great influence on the dynamic stiffness and damping coefficient, and the deeper scour depth increases, the more remarkable influence on the results. Besides the removal of soil around CCPFs resulting from scour effect, it also shows that the change of stress history will further weaken the bearing capacity of composite foundation and enlarge the dynamic response. Thus, ignoring the change of stress history would result in an overestimate of the dynamic impedance. And stress history is also proved to be of great significance to increase the resonant response of composite foundation, while has little influence on the resonant frequency.