An analysis of railway track behaviour based on distributed optical fibre acoustic sensing

Trackside monitoring of railways provides useful data for understanding the condition and mechanical behaviour of railway track, prior research has shown that railway track performance varies significantly along its length, primarily owing to changing support conditions. Understanding the changing performance along track offers the potential for improved track design and maintenance. Different technologies are used to investigate this. For example, inertial sensors, or high-speed filming with digital image correlation (DIC) for track deflection, and traditional strain gauges for loads. The latter usually rely on in-situ calibration. These techniques are suitable for measurements at discrete locations along the track length but are not suited to measuring performance variability even along a few hundred meters of a railway line. This paper investigates the use of a recently developed sensing system known as distributed acoustic sensor (DAS) that uses optical fibres. This method has the potential to be used over very long lengths of track; offers high sample rates; and has a gauge length and spatial resolution suitable for investigating the load-deflection behaviour of the track. This study presents DAS optical fibre strain measurements from a study site and presents novel methods for determining the rail deflection and the load per sleeper end. The DAS results are compared with point location measurements using a traditional strain gauge and deflections determined using imaging and DIC. The DAS system offers reliable distributed strain measurement that convert to estimates of track deflection and load with the potential for continuous spatial and temporal coverage over significant lengths of track. (C) 2020 Elsevier Ltd. All rights reserved.

铁路的轨旁监测为了解铁路轨道的状况和力学行为提供了有用的数据。先前的研究表明，铁路轨道的性能沿其长度有显著差异，这主要是由于支撑条件的变化。了解轨道性能的变化为改进轨道设计和维护提供了可能。人们使用不同的技术来研究这一问题。例如，使用惯性传感器，或采用数字图像相关（DIC）技术进行高速拍摄以测量轨道挠度，以及使用传统应变仪测量荷载。后者通常依赖现场校准。这些技术适用于轨道长度上离散位置的测量，但不适用于测量即使是几百米铁路线的性能变化。本文研究了一种最近开发的使用光纤的分布式声学传感器（DAS）传感系统的应用。这种方法有可能用于很长的轨道；提供高采样率；并且具有适合研究轨道荷载 - 挠度行为的标距长度和空间分辨率。本研究展示了来自一个研究地点的DAS光纤应变测量结果，并提出了确定钢轨挠度和每个轨枕端部荷载的新方法。将DAS的结果与使用传统应变仪进行的点位置测量以及使用成像和DIC确定的挠度进行了比较。DAS系统提供可靠的分布式应变测量，可转换为轨道挠度和荷载的估计值，有可能对相当长的轨道进行连续的空间和时间覆盖。（C）2020爱思唯尔有限公司。保留所有权利。