Experimental Study on Ballast Breaching in Railway Embankments Under Flood Overtopping

Flood-induced ballast breaching poses a serious risk to railway embankments, yet its failure mechanisms remain insufficiently understood. This study provides a preliminary investigation into the overtopping response of ballasted embankments through reduced-scale flume tests conducted under a constant inflow of 25 m3/h. Two configurations were examined: one without sleepers (Case A) and one with concrete sleepers (Case B). Both followed the typical sequence of initiation, acceleration, progression, and stabilization, but with distinct differences: Case A failed rapidly with widespread slope erosion, whereas Case B showed delayed initiation but concentrated scour between sleepers, eventually exposing track components. These findings suggest that sleepers play a dual role, delaying large-scale failure while redirecting hydraulic forces into localized erosive jets. The results offer early insights into ballast breaching under overtopping and point to the need for further research at larger scales and under more realistic flood conditions to guide railway flood resilience strategies.