The deterioration of a rail track due to large dynamic wheel loads is inevitable over the years, and one that leads to frequent and high maintenance costs. This problem is more critical in isolated rail track locations such as bridges and tunnels where the substructure is much stiffer than the surface track assembly. One measure used to minimize track deterioration is to place geosynthetic inclusions such as rubber mats under the layer of ballast. In this study, cyclic loads from fast and heavy haul trains were simulated on stiffer track foundation conditions using a large-scale process simulation triaxial (prismoidal) apparatus (PSPTA) to investigate the 2 performance of ballast improved by rubber mats locally manufactured from recycled tires. The laboratory results indicate that the energy absorbing (damping) characteristics of rubber mats reduce the amount of deformation and degradation of ballast under stiffer track conditions. The study shows that rubber mats distribute the stress applied from moving trains more uniformly by increasing the effective contact area, which then reduces the dynamic amplification of applied vertical stress and contributes to much less ballast degradation.

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Recycling waste materials for transport infrastructure such as coal wash (CW), steel furnace slag (SFS), fly ash (FA) and recycled tyre products is an efficient way of minimising the stockpiles of waste materials while offering significant economic and environmental benefits, as well as improving the stability and longevity of infrastructure foundations. This paper presents some of the most recent state-of-the-art studies undertaken at the University of Wollongong, Australia on the use of waste materials such as (a) CW-based granular mixtures (i.e. SFS + CW, CW + FA) for port reclamation and road base/subbase and (b) using recycled tyre products (i.e. rubber crumbs, tyre cell, under-sleeper pads and under-ballast mats) to increase track stability and reduce ballast degradation. Typical methods of applying these waste materials for different infrastructure conditions are described and the results of comprehensive laboratory and field tests are presented and discussed. Cite this articleIndraratna B, Qi Y, Tawk M et al. Advances in ground improvement using waste materials for transportation infrastructure.

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