考虑应力历史的冲刷对沉箱加桩复合基础水平振动特性影响研究

水流的冲刷效应会导致桩身周围土体的减少及土体应力状态的改变，而对沉箱加桩复合基础的动力特性产生显著的影响。提出了动力Winkler模型，建立了沉箱加桩复合基础受冲刷后考虑应力历史改变影响的动力阻抗计算方法，并通过与海绵边界动力有限元方法的对比，验证了其合理性。对沉箱加桩复合基础工程实例计算结果表明，冲刷对复合基础的动刚度及阻尼有比较显著的影响，且随着冲刷深度的加大，影响更为显著。仅考虑基础侧向土体的减少是不够的，应力历史的改变还会进一步弱化基础承载特性，从而放大结构动力响应，对忽略土体应力历史改变而计算的动力阻抗值是相对偏大的，且应力历史的改变会明显增加基础的共振幅值，但对共振频率大小无明显影响。

Scouring effects on lateral vibration of caisson-piles composite foundation considering stress history of sand

Scouring effect has a significant impact on the lateral vibration of caisson-piles composite foundation because of the change in stress history and the reduction of soils around the foundation. Based on the dynamic Winkler model proposed by author, a computational method of the dynamic impedance of caisson-piles composite foundation influenced by scouring effect with considering stress history is developed. Then sponge boundary dynamic FEM are used to validate the theoretical results. Finally, the proposed procedure is used to analyze a practical engineering. The results show that scouring effect has a significant impact on the dynamic stiffness and damping coefficient, and the more scour depth increased, the more remarkable influence on the results. This implies that it is not enough to only consider the loss of soil around the composite foundation for scouring effect, the change of stress history can further weaken bearing capacity of composite foundation and enlarge the dynamic response of structure, thus ignoring the change of stress history will result in an overestimate of value of dynamic impedance, and the change of stress history accompany with an apparent increase in amplitude of resonant response of composite foundation, while it has no effect on the value of resonant frequency.