Monitoring of ballasted rail track with geosynthetic reinforcement
Large repetitive stresses induced from heavy train traffic can cause significant degradation of ballasted rail tracks, leading to poor track geometry and stability. This, in turn, results in decreased track performance and increased maintenance costs. Inclusions of geosynthetics in the track substructure can decrease the impact of these adverse effects. Thus, understanding the effects of geosynthetic reinforcement becomes necessary for improved design procedures and construction practices for ballasted rail tracks. However, the complex nature of the stress-strain response of composite track system is often difficult to assess using only laboratory tests on reduced-scale models. It is imperative to also understand this behaviour through in-situ monitoring of rail tracks. A series of full-scale field experiments was undertaken on track sections near Singleton, New South Wales to investigate the effects of geosynthetic reinforcement on the performance of the track. These experimental track sections were built on subgrade soils with varying stiffness, and various types of geosynthetics were installed at the ballast-subballast interface. Transient and accumulated deformations of the track substructure as well as variation of traffic-induced stresses in the track were routinely monitored. It was found that geogrids can decrease vertical strains of the ballast with obvious benefits of reduced track maintenance costs. It was also found that a few selected types of geogrids can be effectively used for soft subgrade soils.