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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。
The scouring effect of water flow will lead to the reduction of soil around the pile body and the change of soil stress state, but will have a significant impact on the dynamic characteristics of the caisson plus pile composite foundation. The dynamic Winkler model is proposed and the calculation method of dynamic impedance considering the change of stress history after caisson plus pile composite foundation is established. The rationality of the method is verified by comparison with the spontaneous boundary dynamic finite element method. The calculation results of caisson plus pile composite foundation engineering show that the erosion has a significant impact on the dynamic stiffness and damping of the composite foundation, and the impact becomes more significant as the erosion depth increases. Considering only the reduction of foundation lateral soil is not enough, the change of stress history will further weaken the foundation bearing characteristics, so as to amplify the dynamic response of the structure and neglecting the change of soil stress history, the calculated dynamic impedance is relatively large, And the change of stress history will obviously increase the basic resonance amplitude, but it has no obvious influence on the resonance frequency.