Railway Ballast Damage Detection Based on the Vibration Measurement of In-situ Sleepers

Ballasted track system is one of the most important 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 fast and efficient methods are available for monitoring railway level and alignment, rail gauges, corrugation, etc. However, the detection of ballast damage still relies on visual inspection and destructive core test. Although extensive research has been carried out on the development of non-destructive methods of ballast evaluation, demand remains for a commonly accepted such method. The current practice in Hong Kong is for railway inspectors to carry out a detailed site survey at locations reported to have problems (e.g., abnormal train vibration reported by drivers or passengers). However, such visual inspections are only able to identify surface damage to ballast, track geometry and rail twist problems. Ballast damage under the sleeper loading area and/or ballast shoulder, which can affect track stability and deteriorate riding quality, is extremely difficult, if not impossible, to detect through visual inspection. Core test is destructive, expensive, time-consuming and highly disruptive to traffic. A fast real-time ballast damage detection method that could be implemented by inspectors with simple equipment would provide valuable information that would help engineers to assess the safety and riding quality of ballasted track systems. The main objective of the proposed project is thus to develop a handy method of ballast damage detection based on the measured vibrations of sleepers through simple impact hammer tests. The stiffness that ballast provides in supporting a sleeper depends on its size and packing level. Research has proved that changes in this stiffness will induce detectable changes in the vibration characteristics of the sleeper. In the proposed project, research will be carried out to extract information on ballast damage through the vibration measurement data of in-situ sleepers.