Effect of increase in load and frequency on the resilience of railway ballast

Sun, Qideng; Indraratna, Buddhima; Ngo, Ngoc Trung

doi:10.1680/jgeot.17.p.302

Cited by 47 publications

(21 citation statements)

References 23 publications

(33 reference statements)

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“…As expected, the maximum ballast breakage occurs in the 313 top layer, and it decreases in the middle and bottom layers as the induced impact loads attenuate 314 with depth. Figure 11 shows a large increase in ballast breakage when the drop height of the 315 hammer increases (increased impact energy); this agrees with the findings of a previous study 316 using a large-scale triaxial apparatus where ballast breakage was observed to increase with an 317 increase in cyclic loads (Sun et al 2018). 318…”

Section: Measured Lateral Deformation 281supporting

confidence: 82%

“…It is seen that the calculated values of ∆ 3 vary from 10-20 kPa. It 463 is noted that the ASTM D4767-11 recommends the use of a correction factor for rubber membrane 464 stiffness when determining the deviatoric stress in triaxial testing; for ballast assemblies, the 465 required correction for deviator stress is around 10-15 kPa (Lackenby et al 2007, Sun et al 2018. 466…”

Section: Conclusion 401mentioning

confidence: 99%

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Improved performance of ballasted tracks under impact loading by recycled rubber mats

Ngo

Indraratna

Rujikiatkamjorn

2019

Transportation Geotechnics

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Ballasted tracks at transition locations such as approaches to bridges and road crossings experience increasing degradation and deformation due to dynamic and high impact forces, a key factor that decreases the stability and longevity of railroads. One solution to minimise ballast degradation at the transition zones is using rubber energy absorbing drainage sheets (READS) manufactured from recycled tyres. When placed beneath the ballast layer, READS distributes the load over wider area and attenuate of the load over a longer duration thus decreasing maximum stress, apart from reducing the energy transferred to the ballast and other substructure components. Subsequently, the track substructure experiences less plastic deformation and degradation. These mats also provide an environmentally friendly and cost-effective alternative. In this study, a series of large-scale drop hammer impact tests was carried out to investigate how effectively the READS could attenuate impact loads and help mitigate ballast deformation and degradation. Soft and stiff subgrade were used to investigate the loaddeformation response of ballast (with and without READS), subjected to impact loads from a hammer dropped from various heights (hd =100 -250 mm). Laboratory test results show that the inclusion of READS helps to reduce the dynamic impact load transferred to the ballast layer resulting in significantly less permanent deformation and degradation of ballast, apart from significant attenuation of load magnitude and vibration to the underlying subgrade layers.

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Section: Measured Lateral Deformation 281supporting

confidence: 82%

Section: Conclusion 401mentioning

confidence: 99%

Improved performance of ballasted tracks under impact loading by recycled rubber mats

Ngo

Indraratna

Rujikiatkamjorn

2019

Transportation Geotechnics

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“…Past studies have been carried out to investigate the effects of the loading characteristics (i.e. monotonic or cyclic loads) on the shear stress-strain responses of railway ballast (Lackenby et al 2007;Sun et al 2018;McDowell and Li 2016, Powrie et al 2007, Biabani et al 2016. Based on an extensive laboratory testing program, the volumetric strains of ballast under monotonic and cyclic loading conditions and at different confining pressures have been evaluated, as shown in Figure 1.…”

Section: Behavior Of Ballast Subjected To Monotonic and Cyclic Loadingsmentioning

confidence: 99%

“…The ballast layer is commonly composed of crushed granular aggregates having a typical thickness of 300mm and is placed underneath the track super-structure and above the capping (subballast) or subgrade. 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).…”

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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“…The breaking of ballast, including particle crushing/splitting, and severe attrition of aggregates significantly influence the shear strength of ballast (Lackenby et al 2007, Lu and McDowell 2010, Xiao et al 2014a, Ishikawa et al 2011, Sun et al 2018. Indraratna et al (2005) conducted largescale triaxial tests to study the influence of confining pressure (lateral confinement) on the degradation of ballast under cyclic loading.…”

Section: Introductionmentioning

confidence: 99%

Performance of Ballast Influenced by Deformation and Degradation: Laboratory Testing and Numerical Modeling

2020

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This paper presents a study on the deformation and degradation responses of railway ballast using largescale laboratory testing and computational modeling approaches. A series of large-scale triaxial tests were carried out to investigate the ballast breakage responses under cyclic train loading subjected to varying frequencies, f=10-40 Hz. The role of recycled rubber energy-absorbing mats (REAMs) on reducing ballast breakage was also examined. Laboratory test results show that the ballast experiences significant degradation (breakage) and deformation, while the inclusion of REAMs can reduce the ballast breakage up to about 35%. Numerical modeling using the coupled discrete-continuum approach [coupled discreteelement method-finite-difference method (DEM-FDM)] is introduced to provide insightful understanding on the deformation and breaking of ballast under cyclic loading. Discrete ballast grains were simulated by bonding of many circular elements together at appropriate sizes and locations. Selected cylinders located at corners, surfaces, and sharp edges of the simulated particles were connected by parallel bonds; and when those bonds were broken, they were considered to represent ballast breakage. The subgrade and rubber mat were simulated as a continuum media using FDM. The predicted axial strain εa and volumetric strain εv obtained from the coupled DEM-FDM model are in good agreement with those measured in the laboratory. The model was then used to explore micromechanical aspects of ballast aggregates including the evolution of particle breakage, contact force distributions, and orientation of contacts during cyclic loading. These findings are imperative for a more insightful understanding of the breakage behavior of ballast from the perspective of microstructure characteristics of discrete particle assemblies. Introduction

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Effect of increase in load and frequency on the resilience of railway ballast

Cited by 47 publications

References 23 publications

Improved performance of ballasted tracks under impact loading by recycled rubber mats

Improved performance of ballasted tracks under impact loading by recycled rubber mats

Advancement of Rail Ballast Testing Methodologies and Design Implications

Performance of Ballast Influenced by Deformation and Degradation: Laboratory Testing and Numerical Modeling

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