| This study focuses on the three-dimensional(3-D)characteristics of lateral transient vibration of large diameter piles.Firstly,a 3-D pile-soil model in Cartesian coordinate system is established.Then,the elastic wave equations and the fixed solution conditions of the pile-soil model are obtained according to the elastic theory.To absorb the reflected waves from artificial boundaries,the second-order Higdon absorbing boundary condition is applied herein,which not only satisfies the needs of the research and reduces the number of computing units,but also improves the computing efficiency.Then,based on the boundary and initial conditions,the numerical solution is obtained using staggered grid finite difference method(SGFDM).The accuracy and feasibility of the numerical simulation is corroborated by comparing calculation results with measured curves.The wave snapshots at different time are obtained by the SGFDM,which give a visual interpretation of wave propagation in the pile-soil system.Manifestations and influence factors of three-dimensional effects are systematically analyzed.The optimal sensor location for receiving signals is ascertained,which is subjected to the minimiun 3-D interference.The influencing factors of the phase of the reflected wave from the bottom of the pile are studied and the superiority of the transverse wave in the discrimination of shallow defect is proved by comparing with longitudinal transient vibration of pile-soil system.Dynamic stiffness and damping at pile top are systematically investigated by changing the parameters of pile-soil system,such as Young’s modulus of the pile,the soil underneath pile toe and the layered surrounding soil,etc.The dynamic characteristics of the lateral transient vibration of large diameter piles are comprehended.At last,the stress wave propagation characteristics and dynamic characteristics of pile top in defective piles are discussed. |
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