Vulnerability of interspersed Railway Tracks Exposed to Flood and Washaway Conditions

Railway networks around the world have initially adopted timber sleepers for railway line construction. With time, those timbers deteriorate and emit carbon back to the environment. At present, it is difficult in practice to seek cost-effective hardwood sleepers to replace rotten timber sleepers in time. As a temporary solution, many rail infrastructure managers apply an interspersing method of track maintenance. The interspersing technique is a spot replacement of old timber sleepers with concrete or composite counterparts. This technique is often used as a temporary maintenance for secondary railway lines such as yards, balloon loops or siding. In practice, the interspersed tracks can deteriorate when the tracks are exposed to heavy rains and floods due to the difference in sleeper dimension and stiffness. Under extreme flood events, ballast washaway can be often observed. This study is the world first to demonstrate the vulnerability assessment of interspersed sleeper railways using non-linear finite element simulations, STRAND7. Two moving point loads representing an axle load along each rail have been established to investigate the worst-case, potential instabilities for impaired performance of sleepers and differential settlement of the track. In this study, the emphasis is placed on the effect of ballast washaway on the dynamic displacements and accelerations of rails. The insight will help track engineers develop appropriate climate change adaptation method and policy for versatile operations of interspersed railway tracks facing extreme rainfall and flooding conditions.