软黏土中沉井加桩复合基础水平非线性动力响应分析

摘要

Nonlinear dynamic analysis model for caisson and pile groups are established respectively based on the Winkler foundation model,and the nonlinear dynamic analysis model of composite caisson-piles foundation is developed by combining the displacement and resultant force compatibility conditions.All the impedance functions adopted in the model are frequency independent,which can be conveniently applied in a standard time domain analysis.Comparison with 3D dynamic finite element simulations with sponge boundary demonstrates the reliability of the nonlinear analysis model.From caisson-piles foundation case study,pile groups under the caisson is proved to be of significance to improve the dynamic response of caisson according to the spectrum curve of dynamic displacement.It also shows that the layout of pile groups have a significant effect on the dynamic response of the composite foundation when quantity of material keeps constant,especially in low frequency region.%基于Winkler地基模型分别建立了群桩及沉井非线性动力分析模型,然后结合二者位移及力协调条件得出沉井加桩复合基础非线性动力分析模型.模型参数独立于频率,能够有效地运用于时程动力响应分析.同时,采用海绵边界动力有限元方法验证了该模型的合理性.对比沉井及沉井加桩复合基础算例中频谱曲线显示沉井底部加桩能够明显改善沉井基础的动力受力特性,且材料一定时底部群桩的布置形式对沉井振动特性改善效果存在一定影响,尤其在低频区域影响较为明显.