IMPROVEMENT OF BALLASTED TRACKS USING SLEEPER PADS

INVESTIGATIONS AND EXPERIENCES IN GERMANY

Abstract

Despite the long history of conventional, ballasted railway superstructures further development is needed. The requirements like convenient deformation behaviour (settlements), low-priced maintenance and low noise emissions (air-born and structure born) have been boosted continuously especially for high speed applications. The track-settlement behaviour is influenced by the service conditions and the ballast pressure within the contact area between sleeper and ballast. The contact pressure can be reduced by increasing the contact area or by adding additional resilient components within the superstructure to activate greater load distribution by the rails. Qualified sleeper pads (USP under sleeper pads) give possible solutions. Measurements at field tests in Germany show a better track settlement behaviour. Furthermore additional resilient elements like sleeper pads have great influence on the dynamic vibration behaviour. The vibration velocities have been measured by special ballast stones equipped with accelerometers. Results concerning tracks with additional sleeper pads are available up to 160 km/h and have been compared with measurements performed on tracks with resilient rail pads. Requirements for sleeper pads are resistance against pressure
peaks by ballast stones, durable resilient properties, sufficient vibration behaviour and applicability for conventional construction and maintenance procedures. The experiences born
by laboratory tests and by test sections in revenue lines have been accounted for the new composed technical delivery conditions of the German Railways DB-AG for sleepers equipped with sleeper pads.