Use of Recycled Rubber Granulates in Railway Subballast for Improved Track Performance

As current ballasted tracks are inadequate for supporting Australia’s faster, heavier freight trains, there is an urgent need to develop innovative and sustainable alternatives for transport infrastructure. This paper presents a novel solution for increasing the stability and resiliency of railways by developing a sustainable energy-absorbing subballast layer (SEAL) using recycled tire rubber granulates, steel furnace slag, and coal wash to replace traditional rockfill as subballast. The engineering properties of the track incorporating SEAL were investigated through large-scale laboratory tests (i.e., prototype cubic triaxial tests) and a rheological model. The test results and model simulation confirm that the inclusion of recycled rubber granulates actively increases the efficiency of dissipating energy, decreases ballast breakage, vibrations, and the propagation of dynamic loading within the substructure depth. Also, 10% by weight was found to be the optimal rubber content within SEAL to increase the energy-absorbing capacity of the track foundation and decrease the lateral displacements of the track, while reducing the amount of ballast breakage and maintaining an acceptable settlement.