轨道—高架桥—饱和地基周期结构振动带隙及振动传播特性研究

Vibration filtering property exist in periodic structures, thus vibration cannot propagate freely within some frequency ranges, which are called band gaps. The formulation mechanisms and the calculation methods for the band gaps constitute the phononic crystal theory, which provides a new solution to the vibration predicting and controlling of the elevated high-speed railway lines. Utilizing its periodicity, the elevated railway line is divided into the periodic track cell, the periodic viaduct cell and the periodic ground cell. The band-gap behavior and band formulation mechanism of the periodic cells are investigated using the phononic crystal theory. After coupling the periodic structures formed by the periodic cells, an analysis model for the coupled vibration of the train, track, viaduct and the saturated layered ground is established. Using the established model, the coupled responses of the periodic elevated-railway structures are solved for the excitations of high-speed trains. Meanwhile, the propagation and attenuation characteristics of vibrations in the elevated railway structures and the saturated layered ground are analyzed. The correspondences between the peak frequencies of the responses and the band gap distributions of the periodic cells are determined, which leads to the optimization of the band gaps of the periodic cells so that the vibrations of the elevated railway structures and the saturated ground can be significantly decreased. The presented research will reveal the vibration-propagation characteristics of the elevated railway lines from the perspective of the band-gap behavior of periodic structures. Furthermore, new theoretical guidelines and technical supports will be provided for the control of the structural and the environmental vibrations of the elevated railway lines.

周期结构中存在振动带隙，带隙频率范围内的振动无法传播，带隙理论和带隙算法构成了声子晶体理论。声子晶体理论可为高架高速铁路振动的预测和控制提供新思路。本项目利用高架线路系统的周期特性，将其划分为周期轨道单元、周期桥梁单元和周期地基单元，引入声子晶体理论研究各周期单元的振动带隙和形成机理。在此基础上，自下而上耦合各周期单元形成的周期结构，建立列车—轨道—高架桥—饱和成层地基全耦合振动分析模型，求解高速列车荷载下高架线路周期结构的耦合动力响应，研究高架线路结构和饱和成层地基的振动传播和衰减规律；分析振动响应峰值频率与振动带隙分布的对应关系，优化组合高架线路系统的振动带隙，进而降低高架线路结构和饱和地基的振动响应水平。本项目研究成果可从周期结构振动带隙的角度揭示高架线路系统的振动传播特性，同时可为解决高架线路结构和环境振动问题提供新的理论依据和技术支持。

高架列车线路引起的环境振动问题日益引起关注，列车荷载经由轨道和桥梁结构传至群桩基础并引起地基环境振动，荷载传递路径长，环境振动预测分析难度大。本项目围绕高架铁路线路引发软土地基环境振动中的关键科学问题，分别解析了列车-轨道-桥梁周期结构体系和群桩基础-饱和地基体系，并通过桥墩耦合二者形成了列车-轨道-高架桥-群桩基础-饱和地基全耦合周期体系，解析预测了列车运行引发高架线路结构和三维饱和地基的频域和时域振动响应。结合温州市域高架线路工程实际，实测了桥梁结构和地基环境振动水平，与预测结果对比验证了列车-轨道-高架桥-群桩基础-饱和地基周期模型的有效性。揭示了轮轨作用力经由轨道结构、桥梁结构和群桩基础并最终引发饱和地基振动响应全过程的特征频率变化，明确了高架线路轨道、桥梁结构以及饱和地基振动速度的传播和衰减特性，给出了轨道结构优化选型建议。研究表明桥梁结构和地基环境振动的特征频率为两端弹性支承箱梁的一阶挠曲自振频率、轨道板/板下垫层的共振频率以及桥墩的一阶挠曲自振频率，橡胶垫减振道床既能有效降低桥梁支座反力又不至于引起过大的钢轨动挠度和扣件上拔力，适用于高架轨道结构。本项目建立的研究模型和主要研究结果可为分析和解决高架线路结构和环境振动问题提供有效工具和理论依据。