Discrete element modelling of under sleeper pads using a box test

Li, Huiqi; McDowell, G. R.

doi:10.1007/s10035-018-0795-0

Cited by 59 publications

(49 citation statements)

References 34 publications

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“…For a given scanned particle surface, PFC3D is able to create a 'clump' of the same shape by using the algorithm of Taghavi [41]. The detail of generating a clump with irregular shape is given by Li and McDowell [10]. The classic Hertz-Mindlin contact model [38] is used as the contact model and the particles are given a Poisson's ratio of ν = 0.25 and a shear modulus of G = 28 GPa which are typical values for quartz.…”

Section: Dem Simulationsmentioning

confidence: 99%

“…The reduction of ballast settlement could significantly reduce the maintenance cost for the railway industry. A number of modifications to the conventional ballast system have been proved to be effective in reducing the permanent settlement, such as adding geogrid reinforcement [5][6][7][8], attaching resilient pads (under sleeper pads) to the underneath of sleepers [9][10][11][12], and adding fibre reinforcement to the ballast [13,14]. This paper aims to explore the possibility of reducing the ballast settlement by simply using layers of ballast with different grading without any additional reinforcement.…”

Section: Introductionmentioning

confidence: 99%

“…The discrete element modelling (DEM) introduced by Cundall and Strack [21] has been progressing rapidly for last few decades as it can provide micro mechanic insight for granular materials. DEM has been successfully used to study the mechanical behaviour of railway ballast under various loading conditions such as triaxial tests [22][23][24][25][26][27], box tests [10,[28][29][30][31][32] and direct shear tests [33][34][35][36]. To find out what is occurring at a micro level for the two-layered ballast system and thus potentially propose an optimum design, DEM is employed in this study to simulate the reported experiments [20].…”

Section: Introductionmentioning

confidence: 99%

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Discrete element modelling of two-layered ballast in a box test

McDowell

2020

Granular Matter

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It has been recently reported that ballast comprising differently graded layers helps to reduce track settlement. The main goal of this paper is to provide micro mechanical insight about how the differently layered ballasts reduce the settlement by employing DEM and thus propose an optimum design for two-layered ballast. The DEM simulations provide sufficient evidence that the two-layered ballast works by preventing particles from moving laterally through interlocking of the particles at the interface of the different layers in a similar way to geogrid. By plotting the lateral force acting on the side boundary as a function of the distance to the base, it is found that the walls in the region of 60-180 mm above the base always support the largest lateral forces and therefore this region might be the best location for an interface layer. However, considering the weak improvement in performance by increasing the thickness of the layer of scaled (small) ballast from 100 to 200 mm, it is suggested that it is best to use the sample comprising 100 mm scaled ballast on top of 200 mm standard ballast as the most cost effective solution.

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Section: Dem Simulationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Discrete element modelling of two-layered ballast in a box test

McDowell

2020

Granular Matter

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“…Additionally, due to the discrete nature of ballast, it is not accurate or realistic to use the finite element method, which simulates the ballast layer as continuous layer [13]. The ballast performance keeps changing due to the ballast degradation (abrasion and breakage) [12,[14][15][16]. In addition, the sliding and rolling of individual ballast particles also influence the performance of the ballast layer [17].…”

Section: Introductionmentioning

confidence: 99%

Discrete element modelling of railway ballast performance considering particle shape and rolling resistance

et al. 2020

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To simulate ballast performance accurately and efficiently, the input in discrete element models should be carefully selected, including the contact model and applied particle shape. To study the effects of the contact model and applied particle shape on the ballast performance (shear strength and deformation), the direct shear test (DST) model and the large-scale process simulation test (LPST) model were developed on the basis of two types of contact models, namely the rolling resistance linear (RRL) model and the linear contact (LC) model. Particle shapes are differentiated by clumps. A clump is a sphere assembly for one ballast particle. The results show that compared with the typical LC model, the RRL method is more efficient and realistic to predict shear strength results of ballast assemblies in DSTs. In addition, the RRL contact model can also provide accurate vertical and lateral ballast deformation under the cyclic loading in LPSTs.

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“…For example, the angle of repose is adopted as an important index in designing silos or tanks for corn stockpiles [1]; in geotechnical engineering, it is usually associated with the internal friction angle when soils or crushed rocks are under their loosest state [2]. Studies on the angle of repose for granular materials have attracted much interest among engineers and researchers over the last few decades [1,[3][4][5][6][7][8][9][10]. Despite the knowledge and understandings about the angle of repose that have been gained so far, there are still some insufficiencies that need further investigations.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Particle Morphology Effect on the Angle of Repose for Coarse Assemblies Using DEM

Chen

Gao

Liu

2019

Advances in Materials Science and Engineering

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The morphologies of coarse particles are usually irregular and play a dominant role in the mechanical behaviors of the particle assemblies. This paper quantitatively studies the effect of particle shape on the angle of repose, which is an important macroscopic parameter for ballast materials, via laboratory tests and numerical simulations by means of the discrete element method (DEM). Forty ballast particle templates and four simply created clump templates are reconstructed using an image-based method and quantified with two shape factors, sphericity and convexity. A series of simulations are conducted with the coefficient of sliding friction between particles changing from 0.2 to 0.6 at an interval of 0.1 to study its influence on various shapes of particles, and an appropriate value of sliding friction coefficient is chosen for the comparison of particle shape effect. The results show that increasing sphericity and convexity can significantly decrease the angle of repose, and the real ballast model gives a more realistic angle of repose behaviors as that of laboratory tests compared to simply created models. By analyzing the characteristics of particle motions and contacts from a microscopic perspective, the mechanism of particle shape attributed to the formation of granular aggregation is also discussed and revealed in this research.

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Discrete element modelling of under sleeper pads using a box test

Cited by 59 publications

References 34 publications

Discrete element modelling of two-layered ballast in a box test

Discrete element modelling of two-layered ballast in a box test

Discrete element modelling of railway ballast performance considering particle shape and rolling resistance

Numerical Study of Particle Morphology Effect on the Angle of Repose for Coarse Assemblies Using DEM

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