When the ballast track on a roadbed with soft cohesive soil is replaced by a ballastless track, outflow of roadbed soil or even roadbed caving may sometimes occur. It has been thought until recently that such degradation happens by cyclic trainloads and water actions. However, details of the phenomenon have not been clarified yet. This paper presents factors that have a strong relation with the degradation of the railway roadbed under ballastless tracks, based on the results of model and element tests. Among these factors, the most dominant one for the degradation of the roadbed under ballastless tracks is the consistency of roadbed soil.

Copyright (c) 2004 Railway Technical Research Institute