Asst. Prof. Chayut Ngamkhanong and Dr. Anand Raj
We are pleased to present to you the Advanced Railway Infrastructure, Innovation, and Systems Engineering (ARIISE) Research Unit at Chulalongkorn University. Established with a commitment to excellence, the ARIISE research uni dedicates itself to pioneering research and advancements in the railway domain, bringing together experts from diverse fields such as civil engineering, mechanical engineering, electrical engineering, materials engineering, architecture etc. Our focus encompasses the intricate and comprehensive study of railways, from fundamental knowledge to innovative systems engineering to shape the future of railway transportation, fostering efficient, safe, and sustainable systems for the benefit of society.
We are proud to introduce our first research article titled, “Nonlinear Dynamic Responses of Ballasted Railway Tracks using Concrete Sleepers Incorporated with Reinforced Fibres and Pretreated Crumb Rubber” that has been published in Nonlinear Engineering in September 2023.
Railway sleepers play a pivotal role in ensuring the stability and durability of railway tracks. However, they are subjected to heavy impact loads due to the passing trains, which over time can lead to damage (Figure 1). Addressing this challenge is crucial to enhance the longevity and safety of rail infrastructure. One of the promising solutions to mitigate these concerns is through construction material engineering research specifically by using fibre-reinforced concrete sleepers enhanced with pretreated crumb rubber. These specially designed sleepers exhibit remarkable impact resistance, making them more resilient against high-magnitude impact loads commonly encountered during train movements.
Figure 1 Failure of sleeper due to impact load
The implications of this research can profoundly impact the resilience and longevity of railway infrastructure, representing a significant stride towards the future of sustainable and efficient rail transport. The study meticulously examines the dynamic behaviour of ballasted railway tracks under varying conditions, emphasizing the enhancements achieved by sustainable material inclusions.
By incorporating specific proportions of pretreated crumb rubber along with steel and polypropylene fibres, we can optimize the sleeper’s resistance capabilities. We have employed the stress-strain relationship of materials that can be used for further analysis (Figure 2). We have also performed drop weight impact test on prisms to discern the ideal blend that offers the most effective cost-to-impact energy ratio. The environmental benefit of adopting these materials compared with ordinary concrete sleeper is presented in Table 1.
Figure 2 Stress-strain curve of materials
| Sleeper Type | Manufactured Sand Saved in tonne/ kilometre of track | Crumb Rubber Used tonne/ kilometre of track | Embodied carbon in kg CO2 /km of track | Percentage reduction in embodied carbon in kg CO2 /km of track |
| Ordinary concrete sleeper | 0 | 0 | 67307 | – |
| Rubber concrete sleeper | 15.99 | 3.8 | 55324.3 | 17.8 |
| Polypropylene fibre reinforced rubber concrete sleeper | 16.3 | 3.8 | 55982.18 | 16.82 |
| Steel fibre reinforced rubber concrete sleeper | 15.91 | 3.8 | 80525.69 | -19.63 |
A numerical model has been constructed to simulate the behaviour of ballasted tracks incorporated with these innovative sleepers, as shown in Figure 3. The simulations were conducted using the ANSYS-LS-DYNA software, incorporating dynamic strain rate-dependent material parameters. This aids in achieving a more accurate representation of real-world scenarios. This model has undergone rigorous validation, harmonizing both simulation outcomes and actual field measurements.
This comprehensive study highlights the nonlinear effects of increased train speeds on the dynamic responses of the track with innovative sleepers. Notably, these sleepers can help regulate track displacements and stress, ensuring they remain within permissible safety limits. Though this innovative approach may mark a deviation from traditional materials and methods, the preliminary results hold promise. The insights derived from this research illuminate the potential benefits of integrating reinforced fibres and pretreated crumb rubber into railway concrete sleepers. As we look towards the future of railway infrastructure, these findings pave the way for a safer and more reliable railway system, ensuring that when these tracks are commissioned, they not only meet the highest standards of safety and performance but also embody the principles of sustainability and eco-friendliness.
Figure 3 Train-Track Interaction model
The breakthrough discoveries provide new evidence and confidence about utilising rubber concrete sleepers as well as steel and polypropylene fibre reinforced rubber concrete sleepers in modern ballasted railway tracks. The application of fibre reinforced rubber concrete will help rail industry save about 16 tonnes of fine aggregates and decarbonise up to 3.8 tonnes of crumb rubber, thus proving the solutions as an eco-friendly and sustainable alternative to ordinary concrete sleepers, and thereby helping to preserve precious natural materials and by reducing the waste pile of worn-out tyre rubber. The rubber concrete sleepers and fibre reinforced rubber concrete sleepers will have to be put in test on a trial track in the field to assess their performance as part of future research.
For a comprehensive understanding of this study, we encourage you to peruse the detailed paper available on https://doi.org/10.1515/nleng-2022-0320. We welcome any feedback or inquiries regarding our research.
The authors are grateful to the Second-Century Fund (C2F) of Chulalongkorn University, Bangkok, Thailand for funding the current research. This research is funded by Thailand Science Research and Innovation Fund Chulalongkorn University (BCG66210020).