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This paper presents laboratory and field test results on the use of tire cell track foundation (TCTF) consisting of an assembly of infilled rubber tires to reinforce capping material below the ballast layer. Large-scale cubical triaxial tests were carried out with two different infill materials (crushed basalt rockfill and recycled spent ballast) and they were subjected to varying cyclic loading magnitudes and frequencies. A multistage cyclic loading was performed with and without the inclusion of tire cell reinforcement, whereby the cyclic loading was applied in four different stages with 25,000 loading cycles in each stage. In the first two stages, the frequency was increased from 10 to 15 Hz for an equivalent axle load of 25 t. For the third stage, the axle loading was increased to 35 t with a frequency of 10 Hz, which was then increased to 15 Hz in the final stage. The results showed that the TCTF could reduce the vertical stress transmitted to the subgrade layer as well as curtail the vertical and lateral displacement of the ballast layer. The TCTF further stabilized the track without any significant reduction of the resilient modulus of the overlying ballast as the loading and frequency increased. Compared to a traditional track, the TCTF showed a reduction of 40.1% and 28.3% in the breakage index for the crushed latite basalt and spent ballast (i.e., recycled from ballast tips) infilling the tire cells, respectively. Test results confirm that the TCTF can significantly improve the overall track performance, and this could be mainly attributed to the increased confining pressure provided by the tire cell assembly, as well as the enhanced damping properties of the rubber tire inclusions. In addition, the concept of TCTF was tested using a fully instrumented track (20 m long) subjected to the passage of a 22-t locomotive with two fully loaded carriages. The trial section was constructed within a maintenance yard for heavy haul rolling stock located in a western

In Australia, domestic freight transportation has increased by around ten times during the past five decades and led to a significant upsurge in the construction and maintenance activities of railways. Therefore, it is important to consider upgrading the materials and techniques to address the growing requirements effectively. This study reviews the use of recycled-rubber inclusions including Recycled-Rubber Energy Absorbing Grids (REAG) derived from end-of-life rubber conveyor belts from the mining industry as a countermeasure to minimize track damage. A comparative review on the use of traditional polymer geogrids, Under Ballast Mats, and rubber grids in view of reducing track deformation and ballast breakage will be presented to assess the additional benefits of rubber, which include improved resiliency and damping properties in conjunction with interlocking granular particles.

This paper presents a study examining the use of recycled rubber grids to enhance the performance of ballasted tracks. The rubber grids were manufactured from discarded conveyor belt panels using the waterjet cutting process. Different grids with two aperture shapes, i.e., square and circle, and varying effective area ratios were prepared. Large-scale impact tests were conducted on ballast specimens with and without these grids to assess their performance. Results of this study show that incorporating rubber grids in ballast yields numerous benefits. Firstly, they mitigate the high-frequency impact forces through enhanced damping. Secondly, they reduce subsequent vertical and lateral settlements of the ballast assembly. And finally, they minimise the breakage of ballast particles. The study concludes that using recycled rubber grids can improve ballast performance while also offering obvious environmental benefits and promoting the principles of the circular economy.

Ballasted tracks are essential for transporting goods and passengers between major urban areas and ports, but they suffer breakage, fouling and excessive deformation from repeated train loads. This study investigates the effect of loading and frequency on ballast deformation and degradation through lab tests and numerical modelling. A coupling model based on the finite element method and discrete element method is introduced to predict load-deformation behaviour. DEM represents ballast grains, while FEM models the subgrade, accounting for their interactions. The model is applied to analyze a Singleton, Australia track, with numerical results compared to field data for validation.

Facing the high demand for faster and heavier freight trains in Australia, researchers and practitioners are endeavouring to develop more innovative and resilient ballasted tracks. In recent years, many studies have been conducted by the researchers from Transport Research Centre at the University of Technology Sydney (TRC-UTS) to examine the feasibility of incorporating recycled tyre/rubber into rail tracks. This paper reviews three innovative applications using recycled rubber products such as (1) a synthetic energy-absorbing layer for railway subballast using a composite of rubber crumbs and mining by-products, (2) using rubber intermixed ballast stratum to replace conventional ballast, and (3) installing recycled rubber mat to mitigate ballast degradation under the impact loading. Comprehensive laboratory and field tests as well as numerical modelling have been conducted to examine the performance of rail tracks incorporating these innovative inclusions. The laboratory and field test results and numerical modelling reveal that incorporating these rubber products could increase the energy-absorbing capacity of the track, and mitigate the ballast breakage and settlement significantly, hence increasing the track stability. The research outcomes will facilitate a better understanding of the performance of ballast tracks incorporating these resilient waste tyre materials while promoting more economical and environmentally sustainable tracks for greater passenger comfort and increased safety.

This paper aims to investigate the performance of typical cold-formed steel (CFS) beam-to-beam connections between floor bearers and floor joists through a series of full-scale experiments. The investigated connections consisted of a lipped channel (floor joist), an unlipped channel (floor bearer), a thin-walled clip angle (connector), and a self-drilling screw (fastener). In this study, customised T-shaped and H-shaped CFS connection specimens were tested to examine the performance under tension and shear loads, respectively. Two sizes of self-drilling screws, 10 G and 14 G, were used with the selected load bearing clip angle. The fabricated connection specimens were subjected to displacement-controlled tension and shear loads. The experiments uncovered the ultimate connection strengths, load-displacement relationships, and failure mechanisms of the designed CFS connections under the applied loads. Moreover, the experimental tensile and shear strengths of the connections were compared with the strengths predicted by the standard design equations. It was found that the screw pullout on the anchored leg of the clip angle was the main mode of failure under the tensile load. On the other hand, two different failure modes—fracturing of 10 G screws or shear buckling of the cantilevered leg of the clip angle with 14 G screws—were observed in the H-shaped specimen under the applied shear load. Among the designed connection specimens, the maximum tensile load capacity was 30.86 kN and the maximum shear load capacity 88.15 kN. The standard design calculations predicted screw pullout failure under tension, while the shear bucking failure mode of the clip angle under shear load was overlooked.

By-products (wastes or residues) of renewable materials have the potential to be manufactured into higher value fibre insulation products for the Australian market. Currently, such products have been imported for servicing the Australian market. This presents a potential opportunity to divert considerable quantities of waste from landfill and produce a high performance, locally made, low carbon, natural fibre insulation product for the Australian domestic and commercial building industry. This article assesses the hemp-based bulk insulations available in the Australian market.

Biological thin-walled cellular structures, such as hierarchical structures of bone, exhibit unique internal structures that offer lightweight characteristics and high energy absorption capabilities. The compact bone shell can protect against local damage during high-impact events, while the porous cancellous bone is essential in absorbing energy. This research proposed five novel bioinspired cellular structures inspired by the well-arranged structure of femur bones. These structures comprise four distinct cell types: hexagonal honeycomb, re-entrant, hybrid, and hierarchical hybrid cells. A comprehensive numerical model, validated with experimental data, was employed to assess the performance of these structures under uniaxial compression. Some key characteristics were revealed, including peak elastic load, plateau load, energy absorption capacity, Poisson's ratio, and the effect of hierarchical cell size. The results demonstrated that the novel bioinspired structures surpassed the energy absorption performance of traditional designs, such as hexagonal design, re-entrant, and trabecular-bone-inspired structures. This enhanced performance was due to the progressive buckling and collapse mechanisms, showing promising implications for future engineering applications, particularly where energy absorption is of paramount importance.

This paper presents a study on the enhanced performance of ballasted tracks through the implementation of geogrids. A series of large-scale direct shear tests and impact tests was conducted with three distinct types of geogrids. The behavior of ballast was evaluated in terms of shear stress–strain responses and stress concentration using stress sensing sheets. Additionally, a micromechanical analysis utilizing the discrete element method was simulated on ballast assemblies with different geogrid reinforcements. The shear stress–strain responses of ballast simulated from DEM are comparable with those measured from large-scale direct shear tests, indicating that the inclusion of geogrid can enhance the performance of ballast by increasing its shear strength, as well as reducing the vertical displacement and the load distribution with depth. Micromechanical analysis was performed to investigate the influences of geogrids on contact force distribution, coordination number and orientation of contact which could not be captured in a laboratory environment. The use of geogrids in ballasted tracks certainly shows promise for sustainable and efficient railway infrastructure, as evidenced by the experimental and DEM-based findings, offering valuable insights into optimizing track stability and longevity.

This paper presents results obtained from three-dimension finite element modelling (FEM) to study the effects of geogrids on the deformation responses of ballasted tracks. In this study, a series of numerical simulations are carried out on track sections with and without the inclusion of geogrids. Sensitivity analysis was carried on parameters affecting the performance of geogrid, including the axial stiffness, interface property and the location of geogrid placement in the track substructure. The tracks are subjected to moving train loading under 150 kN wheel load travelling at a given speed of 72 km/h. Based on simulation results, it is found that geogrid provides a reinforcing function to rail track primarily in the form of confinement which resulted in reduced lateral displacement in a reinforced track compared to a traditional track. A significant reduction in vertical and lateral displacement is found from the inclusion of a geogrid layer at the ballast and capping interface while the effect of geogrid reinforcement is more pronounced with increased loading cycles. The effects of geogrid stiffness, interface conditions and geogrid placement are studied and it is found that the axial stiffness of geogrid is found to impact overall track deformation while the optimum placement of geogrid is found to directly at the ballast and capping interface.