Performance improvement of rail track substructure using artificial inclusions – Experimental and numerical studies

Indraratna, Buddhima; Nimbalkar, Sanjay; Ngo, Ngoc Trung; Neville, Tim

doi:10.1016/j.trgeo.2016.04.001

Cited by 55 publications

(31 citation statements)

References 40 publications

(65 reference statements)

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“…These irregularities are distinct enough to cause the train wheels to impose impact forces on the rail [49]. To evaluate the effects of these impact forces on ballast deformation and degradation, a series of laboratory tests were carried out using the large scale drop-weight impact testing equipment [27], as shown in Figure 1d.…”

Section: Influence Of Impact Forces and Benefits Of Using Shock Matsmentioning

confidence: 99%

Two Decades of Advancement in Process Simulation Testing of Ballast Strength, Deformation, and Degradation

Indraratna

Ngo

Nimbalkar

et al. 2018

Railroad Ballast Testing and Properties

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This paper describes salient features of a set of large-scale ballast testing equipment developed at the University of Wollongong, Australia, and how the test results and research outcomes have contributed to transforming tracks in the Australian heavy haul and commuter networks, particularly with regards to the strength, deformation, and degradation of ballast. Ideally, ballast assemblies should be tested in prototype scale under actual loading conditions. This is because a reduction in particle sizes for testing in smaller equipment can reduce the internal angle of friction (shearing resistance) of the granular assembly in a macro sense, and the angularity of the particles in a micro sense, and hence the volumetric changes during the shearing process. In response to the worldwide lack of proper test facilities for ballast, the University of Wollongong has, since the early 1990s, designed and built a number of large-scale process simulation triaxial testing rigs. They are all custom made to minimize any boundary effects and also to evaluate the deformation and degradation of ballast, particularly the size, shape, and origin of aggregates used as ballast in Australian tracks. This triaxial process simulation equipment was originally used to characterize the behavior of coarse aggregate used for state railway standards for monotonic loading, but since then it has been fitted with dynamic actuators to simulate actual track conditions involving the true cyclic loading nature while also capturing the wheel-rail dynamics that correspond to high-speed commuter rail and fast heavy-haul operations. These tests invariably demonstrated completely different stress-strain and volumetric characteristics of ballast compared to conventional static or monotonic testing of the same test specimens. AbstractThis paper describes salient features of a set of large-scale ballast testing equipment developed at University of

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Section: Influence Of Impact Forces and Benefits Of Using Shock Matsmentioning

confidence: 99%

Two Decades of Advancement in Process Simulation Testing of Ballast Strength, Deformation, and Degradation

Indraratna

Ngo

Nimbalkar

et al. 2018

Railroad Ballast Testing and Properties

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“…The deterioration (breakage) of ballast is one of the major contributing factors which affect the stability and longevity of railway foundations (Tutumluer et al 2012;Sun et al 2018;Le Pen et al 2011;Ngo et al 2017). The adoption of various forms of geosynthetic inclusions, such as geogrids and rubber energy absorbing drainage sheets (READS) produced from recycled tires to reduce the plastic deformation and breakage of ballast has become increasingly popular worldwide (Navaratnarajah et al 2018;Abadi et al 2019;Indraratna et al 2016). These synthetic inclusions eliminate hard interfaces between ballast aggregates and concrete sleepers or the underlying formation soils, and allow the aggregates to bed into the relatively softer pads, thus increasing the contact surface area of the ballast and reducing ballast stresses.…”

Section: Introductionmentioning

confidence: 99%

Advancement of Rail Ballast Testing Methodologies and Design Implications

Indraratna¹,

Ngo²,

Rujikiatkamjorn³

et al. 2020

Geo-Congress 2020

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Given the limited capacity of available railway tracks in Australia to sustain increasingly faster and heavier trains, the development of innovative and sustainable ballasted tracks is essential for Australian transport infrastructure. Upon repeated train loading, ballast aggregates become degraded and fouled owing to the intrusion of external fines either from the subbase or surface, which decreases track drainage potentially leading to track instability. This paper reviews some advancements in testing methodologies and design implications of ballasted tracks stabilized with artificial inclusions, including geocomposites, energy absorbing rubber mats and end-of-life tires. Measured test data shows that the use of these waste rubber products and geosynthetics provides an appropriate solution for mitigating unacceptable track degradation and for improving sustainable track alignment, apart from reducing the thickness of the ballast layer. Field monitoring data from fully instrumented tracks constructed at Singleton, Australia is presented and discussed. The outcomes of this study contribute to a better understanding of the performance of reinforced ballasted tracks, which will be imperative for the development of more efficient and cost-effective track designs with enhanced safety and passenger comfort. ABSTRACTGiven the limited capacity of available railway tracks in Australia to sustain increasingly faster and heavier trains, the development of innovative and sustainable ballasted tracks is essential for Australian transport infrastructure. Upon repeated train loading, ballast aggregates become degraded and fouled owing to the intrusion of external fines either from the subbase or surface, which decreases track drainage potentially leading to track instability. This paper reviews some advancements in testing methodologies and design implications of ballasted tracks stabilized with artificial inclusions, including geocomposites, energy absorbing rubber mats and end-of-life tires. Measured test data shows that the use of these waste rubber products and geosynthetics provides an appropriate solution for mitigating unacceptable track degradation and for improving sustainable track alignment, apart from reducing the thickness of the ballast layer. Field monitoring data from fully instrumented tracks constructed at Singleton, Australia is presented and discussed. The outcomes of this study contribute to a better understanding of the performance of reinforced ballasted tracks, which will be imperative for the development of more efficient and cost-effective track designs with enhanced safety and passenger comfort.

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“…Geogrids have long been regarded as an effective method of stabilizing ballast because they provide reinforcement and additional confining pressure. The reinforcement effect of geogrids is generally due to the tensile strains generated in the geogrids as the geogrid and ballast particles interlock [31][32][33][34]; this is how geogrids provide vertical and lateral confinement to the ballast grains and thus reduce its deformation [32,35].…”

Section: Introductionmentioning

confidence: 99%

Use of Geogrids and Recycled Rubber in Railroad Infrastructure for Enhanced Performance

Indraratna

Ngo

et al. 2019

Geosciences

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Railway tracks are conventionally built on compacted ballast and structural fill layers placed above the natural (subgrade) foundation. However, during train operations, track deteriorations occur progressively due to ballast degradation. The associated track deformation is usually accompanied by a reduction in both load bearing capacity and drainage, apart from imposing frequent track maintenance. Suitable ground improvement techniques involving plastic inclusions (e.g., geogrids) and energy absorbing materials (e.g., rubber products) to enhance the stability and longevity of tracks have become increasingly popular. This paper presents the outcomes from innovative research and development measures into the use of plastic and rubber elements in rail tracks undertaken at the University of Wollongong, Australia, over the past twenty years. The results obtained from laboratory tests, mathematical modelling and numerical modelling reveal that track performance can be improved significantly by using geogrid and energy absorbing rubber products (e.g., rubber crumbs, waste tire-cell and rubber mats). Test results show that the addition of rubber materials can efficiently improve the energy absorption of the structural layer and also reduce ballast breakage. Furthermore, by incorporating the work input parameters, the energy absorbing property of the newly developed synthetic capping layer is captured by correct modelling of dilatancy. In addition, the laboratory behavior of tire cells and geogrids has been validated by numerical modelling (i.e., Finite Element Modelling-FEM, Discrete Element—DEM), and a coupled DEM-FEM modelling approach is also introduced to simulate ballast deformation.

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Performance improvement of rail track substructure using artificial inclusions – Experimental and numerical studies

Cited by 55 publications

References 40 publications

Two Decades of Advancement in Process Simulation Testing of Ballast Strength, Deformation, and Degradation

Two Decades of Advancement in Process Simulation Testing of Ballast Strength, Deformation, and Degradation

Advancement of Rail Ballast Testing Methodologies and Design Implications

Use of Geogrids and Recycled Rubber in Railroad Infrastructure for Enhanced Performance

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