A rail track system comprises a number of components and, in order to analyse and predict track behaviour, it is essential to understand the function of each component as each will have a major influence on overall track performance. Historically, rail track substructure, particularly the subgrade, has been given less attention than the superstructure despite its importance in track design. This paper presents a full-scale experimental investigation to study the behaviour of subgrade in both saturated and unsaturated conditions, and how this behaviour changes with soil suction. Further, the investigation also studies the role of sand-blanketing during and after repeated flooding events. The results show that as soil suction reduces, flooding results in a continual reduction in both soil stiffness and track stiffness. It is also shown that the introduction of a sand-blanket has limited effectiveness as a drainage material, particularly after prolonged and repeated flooding.

铁路轨道系统包括许多组件，并且为了分析和预测轨道行为，必须了解每个组件的功能，因为每个组件都会对总体轨道性能产生重大影响。从历史上看，尽管铁路轨道下部结构在轨道设计中很重要，但与上部结构相比，铁路下部结构受到的关注要少于上部结构。本文提出了一个全面的实验研究，以研究路基在饱和和非饱和条件下的行为，以及该行为如何随吸力而变化。此外，调查还研究了在反复的洪水事件期间和之后，防沙作用。结果表明，随着土壤吸力的降低，洪水导致土壤刚度和轨道刚度不断降低。