Transition zones in railway tracks are the locations with considerable changes in the vertical support structures. Due to the differential stiffness and settlement in the open track and the engineering structure resulting in the dynamic amplification of the wheel forces, track settlement is usually observed in the approaching zones. The settlement in transition zones is detrimental to the track components and passenger comfort. This paper presents the results of the experimental analysis performed in three transition zones which were in various conditions. The dynamic displacements of rails due to passing trains were measured at multiple points (dynamic profile) in the approaching zones. The device employed is a contactless mobile device for measuring displacements, which is based on the digital image correlation technique. Because the operational parameters of the digital image correlation-based devices are important for measurement accuracy, prior to the in situ measurements, this device was tested in a laboratory to study the influence of the operational parameters, including the elevation/heading angles, the focal length of the cameras, and the measuring distance. After determining the optimal operational parameters for the railway field, multiple-point measurements were performed in the transition zones. The length of the approaching zone was studied first. Also, the dynamic profiles of the embankment–bridge and bridge–embankment transitions were analysed. Finally, by comparing the multiple-point displacements in the approaching zones in different conditions, it was found that the dynamic profile of the rail displacements has a good correlation with the track condition in the transition zone. The results are presented and discussed.

中文翻译：

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过渡区铁路轨道沉降试验分析

铁路轨道过渡区是垂直支撑结构发生较大变化的位置。由于开放式轨道的刚度和沉降差异以及工程结构导致车轮力的动态放大，通常在接近区域观察到轨道沉降。过渡区的沉降不利于轨道部件和乘客舒适度。本文介绍了在不同条件下的三个过渡区中进行的实验分析的结果。在接近区域的多个点（动态剖面）测量由于列车通过而导致的轨道动态位移。所采用的设备是一种用于测量位移的非接触式移动设备，它基于数字图像相关技术。由于基于数字图像相关的设备的运行参数对测量精度很重要，因此在原位测量之前，该设备在实验室中进行了测试，以研究运行参数的影响，包括仰角/航向角、焦距相机的长度和测量距离。在确定铁路领域的最佳运行参数后，在过渡区进行了多点测量。首先研究了接近区的长度。此外，还分析了路堤-桥梁和桥梁-路堤过渡的动态剖面。最后，通过比较不同条件下逼近区的多点位移，结果表明，轨道位移的动态剖面与过渡区的轨道状况具有良好的相关性。结果被提出和讨论。