Abstract:
As train speeds and heavy haul axle loads constantly increase due to market demands, so do the
stresses and strains experienced by track structures. This is especially true for track transitions
that generate high dynamic forces on both the track and vehicles because of poor vertical
track geometry and/or differing track stiffness values on either side of the track transition.
Reducing differential settlement between the two track structures at a track transition is one
method of improving the life of the track, and increasing maintenance intervals. In this study,
rigid polyurethane foam was used to reinforce ballast. Tests were conducted using a dynamic
hydraulic load frame and a single sleeper in a large ballast box subjected to heavy haul axle
loads. Unreinforced, reinforced and 50% reinforced ballast layers of 300 mm depth were tested
to approximately 5 000 000 load cycles. The results showed that rigid polyurethane foamreinforced
ballast exhibited in the order of 60% less settlement for a fully reinforced layer, and
42% less settlement for a half reinforced layer. The use of rigid polyurethane foam (RPF) to
reinforce ballast has a number of benefits that could result in better track geometry and longer
maintenance cycles, in turn resulting in lower life cycle costs.
