A feasibility study on railway ballast damage detection utilizing measured vibration of in situ concrete sleeper

Ballasted track plays an important part in railway transportation systems. Given the importance of railway safety, research work with industrial applications has been carried out. The current railway track monitoring system is comprehensive and efficient methods are available for monitoring railway level and alignment, rail gauge, and so forth. However, the detection of ballast damage still relies on visual inspection and destructive core test. Although visual inspection is useful to identify ballast damage on the surface, ballast damage under the sleepers, which is believed to be the most critical for ballasted track safety, is extremely difficult if not impossible to detect in this way. A practical on-site test that can provide additional information for inspectors or engineers to quantify the “health” status of ballast under sleepers is in great demand. The rail–sleeper–ballast system can be considered as a beam on an elastic foundation. When the ballast under a sleeper is damaged, the stiffness that it should provide to support the sleeper is reduced. As a result, the vibration characteristics of the in situ sleeper will be altered. One possible way of applying this idea to ballast damage detection is to employ a model updating approach. This paper focuses on a feasibility study on the detection of ballast damage utilizing the measured vibration of the in situ concrete sleeper by following the model updating method. This paper reports not only the theoretical development of the proposed methodology, but also the numerical and full-scale experimental verifications. The numerical and experimental verification results are very encouraging, showing that it is possible to quantify the “health” status of ballast by calculating the reduction in stiffness of the ballast under the sleeper. Some observations and discussions based on the verification results are provided at the end of the paper.