Analysis of geometric ballast plate for laboratory testing of resilient track components

Under tie pads (UTPs)have become a common solution for railroad networks across the world to improve track quality and reduce maintenance. Despite the benefits of UTPs in heavy-haul applications, there are currently no testing standards pertaining to UTPs in high axle load environments. The current European standard, the EN 16730:2016, recommends the use of a geometric ballast plate (GBP)in place of actual ballast for several tests. The GBP's lightweight construction and geometric design allows for ease of use and repeatability in laboratory testing. However, GBP and ballast contact with UTPs have not been thoroughly documented within the literature. Therefore, this study aims to compare the relationship between GBP and ballast contact surfaces through a variety of laboratory tests and 3D scanning. Several ballast “blocks” were cast to serve as repeatable ballast specimens for the tests and scans. Top contact surface, pressure distribution characteristics, and geometric properties of the GBP and ballast blocks were compared. Results showed that the GBP generally overestimates the contact characteristics of ballast, resulting in lower pressures, higher contact areas, greater total areas at given depths, and smaller particle spacing than the ballast blocks. Using these results, a more realistic GBP design can be developed. This work will be valuable in establishing more accurate testing methods/support conditions to enable representative, easy, and repeatable laboratory testing of resilient track components.