Volume 36, Issue 4 (July 2008)
Experimental Determination of the Effect of Wet/Dry Ballast on Dynamic Railway Sleeper/Ballast Interaction
As one of the main components of ballasted railway tracks, the concrete sleeper is a cross-tie beam utilized to dissipate the dynamic axle load from the rails to the ballast and the sub-ballast. It interacts with the ballast support under dynamic conditions. This paper presents the dynamic effect on the in-situ concrete sleeper of ballast in wet and dry states. A panel of concrete sleeper laid on an in-situ railway track, constructed at the University of Wollongong, has been chosen to evaluate its dynamic properties using a modal analysis technique. Since the nature of the ballast itself is to have very high drainage properties, the experiments are focused on both dry and very soaked conditions. The moisture content at the sleeper soffit in the former case is approximately 0 %. In the latter case, the ballast is sprayed using ambient-temperature tap water at the rate of 10 mm/h for half an hour. The average moisture content of the ballast sampled after the modal testing at the soffit of the sleeper is 2.63 %. Modal testing was performed before and after spraying in the frequency range between 0 and 1600 Hz. The modal results representing the dynamic railway sleeper/ballast interactions are highlighted.