This paper reports a feasibility study in the use of measured modal parameters of in-situ concrete sleepers to detect possible damage of the underlying railway ballast. There are many methods developed for monitoring and damage detection of the rail track. However, the detection of ballast damage still heavily relies on visual inspection and destructive core test. In this feasibility study, a typical plain ballasted track with concrete sleeper is considered. In the proposed method, ballast under sleeper is modelled as an elastic foundation. Ballast damage is defined as ballast degradation and ballast cementation with the accumulation of fines. When the ballast is damaged, the stiffness provided in supporting the sleeper will reduce, and the vibration characteristic of the in-situ sleeper will be altered. This paper studies the possibility to detect the damage status of ballast under a sleeper by monitoring the vibration of the corresponding sleeper through simple impact hammer test. This paper not only presented the theoretical development but also the numerical verifications.

Innumerable high speed railways have been constructed around the world. The mass railway transportation becomes more and more important to the development of the countries’ economies and societies. Recently, new railway technologies are developing at tremendous speed. For example, China High Speed Rail achieved the world record of 350Kph and the axle load is increased over 25tonnes. Under such a heavy and repeated train loadings, the degradation of ballast is very fast. Once the train speed reaches the critical train speed, the amplitude of the track vibration will be increased significantly, and cause safety problem of the railway system.

More….