Identification of the under-tie pad material characteristics for stress state reduction

The degradation of ballast particles and concrete crossties in heavy-haul railroad tracks poses problems such as inhibiting proper drainage and disturbing track geometry. under-tie pads offer a solution to reduce crosstie–ballast stresses by improving load distribution through the track structure and reducing pressures on ballast particles and the crosstie surface. Despite the emergence of under-tie pads on heavy-haul corridors, optimal characteristics for the reduction of the tie–ballast stress state have not been defined in literature. In this research, several under-tie pad products and generic materials with various thicknesses and hardnesses were studied to identify appropriate properties of under-tie pad products for pressure distribution. The findings from this research provide an insight into how material characteristics influence the pressure mitigation performance of under-tie pads. Results from this study indicate that thickness is the most crucial metric determining under-tie pad performance in reducing ballast degradation; hardness and material type also have an effect, but to a lesser degree.