Vibration-based detection of ballast voids and pockets under railway composite sleepers


After a railway track experiences dynamic loading, the track settles and causes ballast to deform, spread and sometimes damage. Without appropriate maintenance, voids and pockets of ballast underneath railway composite sleepers can establish over time and impair the quality of train services. In this study, the emphasis will be placed on the application of non-destructive vibration-based technology, to investigate and evaluate dynamic characteristics of voided railway composite sleepers, which are the fundamental element to provide track support to railway systems. The study has developed a vibration-based damage detection method to identify ballast voids under railway track sleepers. This method can be easily deployed in the field by using vibration sensors to measure vibration responses. In this study, the assumption is that the time-dependent material degradation negligibly affects the curvature ratios. The dynamic finite element model has been established and validated for railway composite sleepers in the field. A variety of losses of ballast support have been simulated using the validated model. The dynamic mode shape has been analysed to evaluate curvature ratios under different types of ballast losses. Although the method provides positive outcomes, the advantages, disadvantages and limitation of the method are then identified and discussed.