Investigating the effect of railway track ballast and bed conditions on the lateral resistance of timber, concrete, steel, and composite sleepers using a novel test methodology

This study investigates the effect of sleeper (tie) type, ballast condition, and vertical rail restraint forces on sleeper-ballast interaction, which is responsible for lateral resistance behaviour, to support track safety management. Lateral resistance, principally dictated by the sleeper-ballast interaction is a property of ballasted railway track critical to overall track stability, and to the reduction of track buckling risk. Previous investigations of this property have overlooked the restraining effect of the rail which limits the uplift of sleepers during sleeper push tests. A novel single sleeper push tests (SSPT) methodology, utilising a kinematic restraint, has been used to test the lateral resistance of five sleeper types including timber, concrete, steel, and composite. The tests were performed for a range of ballast dimensions and consolidations, with lateral resistance values up to 40 mm displacements presented. The percentage contribution of the sleeper base is calculated for each sleeper, finding reasonable agreement with values found in existing literature. This study has found that for small displacements, concrete and steel sleepers generate similar levels of lateral resistance, with steel sleepers exhibiting increased resistance for extended push distances. Steel sleepers have a concave structure and are found to generate much of their lateral resistance through internal ballast interaction, making them suitable for use in circumstances where the cribs or shoulders are damaged or reduced. Timber and composite sleepers were found to provide lower resistances, approximately 50 % of the peak resistance of concrete sleepers. As railways worldwide are re-engineered to avoid climate change driven infrastructure failures these findings contribute to track safety management by improving buckling mitigation strategies, whilst aiding the selection of more suitable and effective components to alleviate the effects of climate change on the railway track system.