Deformation and degradation response of railway ballast under impact loading - effect of artificial inclusions
Impact forces induced by wheel and/or rail irregularities and abrupt variations in track stiffness may lead to accelerated deterioration of the track components. The use of artificial inclusions such as geosynthetics and rubber-based energy absorbing mats can be an effective way of mitigating ballast degradation and improving the overall track performance. This paper describes a laboratory study carried out using a large-scale drop-weight impact testing apparatus to investigate the deformation and degradation behaviour of railway ballast under impact loading conditions. The effect of artificial inclusions (i.e., rubber mat and geogrid reinforcement) on the ballast response along repetitive impact blows is evaluated and discussed. Results have shown that the ballast deformations are particularly significant along the initial stage of impact loading, which is associated with ballast reorientation and rearrangement and corner breakage of ballast particles. Among the test conditions analysed in the current study, placement of rubber mats at the base of the ballast assembly and a geogrid layer at 100 mm height was found to be the best combination, providing the maximum reduction in the impact-induced ballast strains and particle breakage when compared to those obtained in the absence of artificial inclusions.