Discrete Element Method Evaluation of Granular Crushing Under Direct Shear Test Conditions

Lobo-Guerrero, Sebastián; Vallejo, Luis E.

doi:10.1061/(asce)1090-0241(2005)131:10(1295)

Cited by 91 publications

(36 citation statements)

References 18 publications

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“…(7) can help practicing engineers predict track settlement and simultaneously consider ballast fouling. The discrete element method (DEM) introduced by Cundall and Strack (1979) has been used to model the behavior of ballast (Lim and McDowell 2005;Lobo-Guerrero and Vallejo 2005;McDowell 2006, 2008;Hossain et al 2007;Huang et al 2009b;Indraratna et al 2010). The DEM enables the discrete nature of grains to be modeled by providing an insight into microscale factors, such as particle shape, interparticle movements, and contact force chains developed among particles that cannot be otherwise determined.…”

Section: Proposed Deformation Model Of Fouled Ballastmentioning

confidence: 99%

Deformation of Coal Fouled Ballast Stabilized with Geogrid under Cyclic Load

Indraratna

Ngo

Rujikiatkamjorn

2013

J. Geotech. Geoenviron. Eng.

113

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This paper presents the results of laboratory investigations into the deformation of coal fouled ballast stabilized with geogrid at various degrees of fouling. A novel track process simulation apparatus was used to simulate realistic rail track conditions subjected to cyclic loading, and the void contamination index (VCI) was used to evaluate the level of ballast fouling. The experimental results show that coal fines act as a lubricant, causing grains of ballast to displace and rotate, and as a result, accelerate its deformation. However, coal fines also reduce ballast breakage because of a cushioning effect, that is, by reducing interparticle attrition. The inclusion of geogrid at the interface between the layer of ballast and subballast provides additional internal confinement and particle interlocking via geogrid apertures, which reduces deformation. A threshold value of VCI540% is proposed to assist practitioners for conducting track maintenance. If the level of fouling exceeds this threshold, the geogrid reinforcement significantly decreases its effectiveness and the fouled ballast exhibits a premature dilation. Based on the experimental results, an equation incorporating the VCI was proposed to predict the deformation of fresh and fouled ballast. This equation improves track design and assists in favorable decision support for track maintenance. Additionally, the discrete element method (DEM) was also used to capture the deformation of fouled ballast subjected to cyclic loading, whereas the DEM results were compared with experimental observations. Abstract: This paper presents the results of laboratory investigations into the deformation of coal fouled ballast stabilized with geogrid at various degrees of fouling. A novel track process simulation apparatus was used to simulate realistic rail track conditions subjected to cyclic loading, and the void contamination index (VCI) was used to evaluate the level of ballast fouling. The experimental results show that coal fines act as a lubricant, causing grains of ballast to displace and rotate, and as a result, accelerate its deformation. However, coal fines also reduce ballast breakage because of a cushioning effect, that is, by reducing interparticle attrition. The inclusion of geogrid at the interface between the layer of ballast and subballast provides additional internal confinement and particle interlocking via geogrid apertures, which reduces deformation. A threshold value of VCI 5 40% is proposed to assist practitioners for conducting track maintenance. If the level of fouling exceeds this threshold, the geogrid reinforcement significantly decreases its effectiveness and the fouled ballast exhibits a premature dilation. Based on the experimental results, an equation incorporating the VCI was proposed to predict the deformation of fresh and fouled ballast. This equation improves track design and assists in favorable decision support for track maintenance. Additionally, the discrete element method (DEM) was also used to capture the deformation of ...

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Section: Proposed Deformation Model Of Fouled Ballastmentioning

confidence: 99%

Deformation of Coal Fouled Ballast Stabilized with Geogrid under Cyclic Load

Indraratna

Ngo

Rujikiatkamjorn

2013

J. Geotech. Geoenviron. Eng.

113

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“…In the past decade, DEM has been successfully applied to railway ballast. The early studies of DEM modelling ballast particles [11,12] represented a particle as a simple sphere with the aim of investigating ballast degradation by using the particle replacement method. Lu and McDowell [13] showed that the use of irregular particle shape in DEM could provide more particle interlock and thus gave much reduced particle rotations and displacements.…”

Section: Introductionmentioning

confidence: 99%

Discrete element modelling of under sleeper pads using a box test

McDowell

2018

Granular Matter

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It has recently been reported that under sleeper pads (USPs) could improve ballasted rail track by decreasing the sleeper settlement and reducing particle breakage. In order to find out what happens at the particle-pad interface, discrete element modelling (DEM) is used to provide micro mechanical insight. The same positive effects of USP are found in the DEM simulations. The evidence provided by DEM shows that application of a USP allows more particles to be in contact with the pad, and causes these particles to transfer a larger lateral load to the adjacent ballast but a smaller vertical load beneath the sleeper. This could be used to explain why the USP helps to reduce the track settlement. In terms of particle breakage, it is found that most breakage occurs at the particle-sleeper interface and along the main contact force chains between particles under the sleeper. The use of USPs could effectively reduce particle abrasion that occurs in both of these regions.

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“…The discrete element method (DEM) proposed by Cundall and Strack (1979) has been widely used to examine the micromechanical properties of ballast materials (Lim and McDowell 2005;Lobo-Guerrero and Vallejo 2005;Tutumluer et al 2007;Bhandari et al 2009;O'sullivan and Cui 2009;Lobo-Guerrero and Vallejo 2010;Lu and McDowell 2010;Zhang et al 2013;Huang et al 2013;Tutumluer et al 2013;Mishra et al 2014;Indraratna et al 2015;Ngo et al 2015;Qian et al 2015), among others, but most of these numerical studies focused on fresh ballast. McDowell et al (2006) used the discrete element method to model largescale triaxial experiments of ballast aggregates reinforced with geogrids, and concluded that the DEM approach holds much promise as a tool for investigating granular aggregate assemblies.…”

Section: Introductionmentioning

confidence: 99%