Abstract
When the ballast track on a soft roadbed is replaced with a ballastless track which has high rigidity, outflow of roadbed soil or even roadbed caving may occur. Since the growing process of roadbed degradation under a ballastless track has not been clarified, reasonable countermeasures have not been developed yet.
In this study, we discussed the growing process of the degradation of cohesive-soil roadbed under a ballastless track by performing moving wheel loading tests to simulate actual trainloads. As a result, we confirmed that the roadbed degradation under a ballastless track was caused by the piping-outflow of the surface soil whose effective confinig stress was not increased enough by the dynamic porepressure due to train loads. Thus, we were able to clarify the basic policy on the countermeasures against such degradation.
