Influence of time-dependent material degradation on life cycle serviceability of interspersed railway tracks due to moving train loads

Presently, timber-sleepered tracks are still being adopted in railway networks transporting goods and passengers. However, the deterioration of timber sleepers is evident after years of service due to natural decay; and it is difficult to seek cost-effective hardwood sleepers to replace the aging sleepers. An impermanent interspersed approach is an alternative method used to substitute rotten timbers with concrete sleepers. Although the interspersed tracks offer a cost-effective short-term solution for certain track classes, there are some drawbacks to this practice, since the interspersed track has inconsistent stiffness problems, and the different track decay rate can cause uneven settlement and foundation failure, which can lead to significant track deterioration over time. The emphasis of this study is placed on the long-term behaviour of interspersed track components under repeated train loading. Interspersed track models in three-dimensional space have been developed and validated using a finite element method. The effects of deteriorated railway components (timber, rail pads, ballast) are taken into account to examine the dynamic performance of the interspersed tracks under moving train loads. This study will help rail track engineers better understand the time-dependent behaviour of interspersed tracks, enable a truly predictive track maintenance and improve the reliability of infrastructure asset maintenance and life cycle management.