Laboratory examination of ballast deformation and degradation under impact loads with synthetic inclusions
© 2020 Elsevier Ltd This paper presents a laboratory study on alleviating the deformation and degradation (breakage) of ballast subjected to impact loads using geogrids and rubber mats. A series of drop hammer impact tests are carried out to determine how well the geogrid, under-ballast mat (UBM) or under-sleeper pad (USP) can attenuate impact loads and mitigate ballast degradation. Geogrids to be placed at different locations in a ballast assembly, in combination either with a UBM or a USP are tested. Laboratory test results prove that the inclusion of rubber mats and geogrids decrease the dynamic impact loads transferred to the ballast aggregates and subsequently decrease the degradation (breakage) and deformation of ballast. The tensile strength of geogrids and subgrade stiffness are found to considerably influence the performance of geogrid-reinforced ballast under impact loading conditions. The measured impact forces and accelerations of ballast with and without an artificial inclusion show that rubber mats definitely reduce track vibration (acceleration) and the subsequent deformation and breakage of ballast. These inclusions will not only increase safety and passenger comfort they will also lead to more economical and efficient track designs.