高速铁路过渡段车致弹性波渡越辐射能

The operation practices of the high-speed railway in China and foreign countries indicated that the defects of the track and the subgrade occurred most frequently in transition zones between different track foundation configurations. Even if the track geometry irregularity can be well controlled, the degradation rate of the track and the subgrade in transition zones is obviously higher than that of the normal subgrade or normal bridge zones. A most important physical reason of this phenomenon is the transition radiation of the elastic wave, which is induced by the wheel-rail contact of the high speed trains, due to the track and subgrade inhomogeneity. The mathematical expression of the transition radiation energy of the elastic wave in high-speed railway transition zones due to subgrade stiffness and geometry inhomogeneity will be given in this project. The mathematical model of the heterogeneous elastic media with multi complex interfaces will be established. Based on the assumptions that the load velocity is taken sub-critical and waves are coupled in the interfaces, the solution of the model in the space-frequency domain will be obtained both in the eigen field and the free field. The transition radiation energy flux expression can be derived by the displacement field solution. The influence of the train speed, the stiffness contrast and the incident angle of the elastic waves on the transition radiation energy flux will be studied. Based on these influences, the external force vector of the vehicle-track system can be derived. With the update of the external force vector, the effect of the transition radiation on the vehicle running stability can be investigated. As result the dynamic transition performance of the existed transition zone configuration can be evaluated. The research achievement of this project can be used as the design theoretical basis of the new transition zone configuration.

国内外高速铁路运营实践表明，轨道和路基病害集中于不同轨道基础间的过渡段，即使在保证轨面平顺条件下，过渡段轨道劣化速率及路基病害发生率仍明显高于一般路基段或桥梁段。产生这种现象的一个重要物理原因在于轮轨接触产生的弹性波在过渡段中传播发生渡越辐射现象。本课题将从波动和能量的角度给出高速铁路过渡段刚度变化引起弹性波渡越辐射现象的数学表达。建立过渡段复杂多界面非均匀弹性介质波场计算模型，在亚临界速度移动荷载和界面耦合的条件下，通过本征场和自由场求解波动方程，得到空间-频率域位移场解；通过位移场推导渡越辐射能量流表达式；分析列车运行速度、过渡段刚度差异和弹性波入射角度对渡越辐射能量流的影响规律；将此影响量化为过渡段车辆-轨道系统外力向量修正，分析渡越辐射对过渡段列车运行平稳性影响，评价既有过渡段设计能否满足系统长期动力稳定要求，以期为新型高速铁路过渡段设计提供理论依据。

针对轨道刚度差异及几何非均匀性所引起的过渡段结构服役性能快速劣化和列车运行平稳性降低问题，本课题首先基于弹性波渡越辐射理论，从波动和能量的角度展开研究。以典型高速铁路路桥过渡段结构形式为依据，建立过渡段倾斜界面耦合弹性层渡越辐射模型，模型通过边界条件及界面连续条件实现本征场及自由场求解。本征场为单一介质在列车荷载作用下的稳态振动场，当列车驶经界面时，临界介质间的稳态振动能量差值会成为渡越辐射产生的本源，所激发的自由导波向界面两侧传播并构成自由场，不仅可用于求解渡越辐射所引起的路基附加位移场和应力场，也可用于频域-空间域计算不同荷载移动速度、界面倾斜角度等对渡越辐射能的影响规律。其次，在渡越辐射引发附加应力场推导的基础上，结合多级加载条件下土体累积塑性应变修正模型，提出了能够考虑路基应力历史的过渡段不均匀沉降动态发展计算方法。基于上述研究，可为高速铁路优化既有过渡段结构及新型过渡段结构设计提供参考。.重要结论包括：.（1）渡越辐射能的大小随荷载移动速度增加单调非线性增加，移动荷载速度达到较软侧介质临界波速的74%时，渡越辐射能将超过介质本征场应变能； .（2）近场能量角密度分布形状与界面倾斜角度相关，界面方向为峰值能量区域；全频段渡越辐射能随界面倾斜角度增大而增加，峰值频率向高频移动；.（3）受桥台反射及土体阻尼影响，随深度增加的动应力曲线呈现相位滞后现象，临近桥台的3m范围内为影响偏应力分布的敏感区域；.（4）轨道初始沉降槽出现在距离桥台6m范围内，随着加载循环次数的增加，轨道不均匀沉降增加，且在初始沉降槽附近会出现新的沉降槽。