Recycled Rubber Grids for Improved Performance of Ballasted Tracks
- Publication Type:
- Thesis
- Issue Date:
- 2024
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| Filename | Description | Size | |||
|---|---|---|---|---|---|
| thesis.pdf | thesis | 13.56 MB |
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Railway transportation remains a dominant mode of cargo and passenger transport due to its large capacity, energy efficiency, and low environmental footprint. With increasing numbers of passengers and freight volumes, the demand for robust, resilient, and reliable railway infrastructure has never been greater. However, the physical dynamics of train-track interaction present challenges for railway tracks, particularly the ballast layer, which is subject to a range of stresses, impact forces, and vibrations induced by moving trains. At the same time, end-of-life rubber conveyor belts are now one of Australia's biggest sources of rubber waste, with a significant portion originating from its thriving mining industry. According to the Australian Bureau of Statistics, hundreds of thousands of tonnes of used rubber conveyor belts end up in the waste stream annually.
This research utilised recycled rubber panels derived from used conveyor belts to manufacture rubber grids that could help reinforce ballast aggregates and offer damping for track assembly. The waterjet cutting technique was used to fabricate rubber grids with apertures of different shapes and sizes. Two important parameters were identified for the geometric optimisation of rubber grids: the aperture size (A) and the effective area ratio (KA.eff). A series of large-scale laboratory tests were conducted on ballast specimens with and without rubber grids to assess their performance under direct shear and impact loads. The results indicate that rubber grids can enhance the shear strength and reduce the dilation of ballast aggregates. These grids can also mitigate the detrimental effects of high-impact forces by minimising the deformation and degradation of ballast.
A field trial was then carried out to assess the performance of rubber grids in real-world conditions. Two track sections were constructed with and without rubber grids under the ballast layer. Various instruments were used to monitor the stresses and displacements in both tracks at different depths and locations. The results from the field trial showed a significant reduction in stress in the substructure layers, which could minimise deformation and prevent the breakage of ballast in the long run. Finally, a numerical modelling approach employing finite element analysis was utilised to simulate the behaviour of ballasted tracks reinforced with rubber grids when subjected to cyclic train loads. The outcomes of the finite element models are generally consistent with the field observations. Overall, this doctoral research serves as a comprehensive investigation into the use of rubber grids to enhance the performance of ballasted railway tracks.
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