Three-dimensional characterisation of particle size and shape for ballast

Sun, Yifei; Indraratna, Buddhima; Nimbalkar, Sanjay

doi:10.1680/geolett.14.00036

Cited by 78 publications

(34 citation statements)

References 23 publications

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“…This section summarizes reports from recent studies on a 3D assessment of particle size and shape where a 3D laser scanner has been utilized ( Figure 10). To facilitate 3D analysis, a modified index called 'ellipsoidness' E is proposed by Sun et al [40] and is shown in Figure 11.…”

Section: Effects Of Particle Angularity -Size and Shapesmentioning

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: Effects Of Particle Angularity -Size and Shapesmentioning

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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“…However, the existing 3D roundness indexes usually do not involve corner identification and curvature evaluation [18,46]. In this study, we propose a novel method to evaluate 3D roundness based on local curvature values.…”

Section: Particle Roundnessmentioning

confidence: 99%

3D quantitative shape analysis on form, roundness, and compactness with μCT

2016

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Particle shape plays an important role in determining the engineering behaviour of granular materials. In this regard, characterisation and quantification of particle shape are essential for understanding the behaviour of granular materials. X-ray micro-computed tomography (μCT) enables observation of particle morphology at ever-greater resolutions. The challenge has thus become extracting quantified shape parameters from these rich three-dimensional (3D) images. In this paper, we implement X-ray μCT to obtain 3D particle morphology and utilize image processing and analysis techniques to quantify it at different scales. A novel framework is proposed to measure 3D shape parameters of form, roundness, and compactness. New 3D roundness indexes were formulated from the local curvature on reconstructed triangular surface mesh. Subsequently, this method is utilized to study the change of particle shape by single particle crushing tests on Leighton Buzzard sand (LBS) particles. It is found that compactness value (i.e., sphericity) could be influenced by both form and roundness. Then, the distributions of shape parameters are characterised by Weibull statistics. It shows that single particle crushing tests generate more irregular fragments which have smaller shape parameters with larger variance for the measured shape parameters.

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“…Lots of experimental and theoretical studies have been performed [1][2][3][4][5][6][7][8][9][10][11][12][13][14] to investigate the mechanical behaviour of granular soils. For example, Xiao et al [15] conducted a series of true triaxial tests on the rockfill material under drained loading condition.…”

Section: Introductionmentioning

confidence: 99%

Modelling long-term deformation of granular soils incorporating the concept of fractional calculus

et al. 2015

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Many constitutive models exist to characterise the cyclic behaviour of granular soils but can only simulate deformations for very limited cycles. Fractional derivatives have been regarded as one potential instrument for modelling memory-dependent phenomena. In this paper, the physical connection between the fractional derivative order and the fractal dimension of granular soils is investigated in detail. Then a modified elastoplastic constitutive model is proposed for evaluating the long-term deformation of granular soils under cyclic loading by incorporating the concept of factional calculus. To describe the flow direction of granular soils under cyclic loading, a cyclic flow potential considering particle breakage is used. Test results of several types of granular soils are used to validate the model performance. Abstract Lots of constitutive models exist to characterise the cyclic behaviour of granular soils but can only simulate deformations for very limited cycles. Fractional derivatives have been regarded as one potential instrument for modelling memory-dependent phenomena. In this paper, the physical connection between the fractional derivative order and the fractal dimension of granular soils is investigated in detail. Then a modified elasto-plastic constitutive model is proposed for evaluating the long-term deformation of granular soils under cyclic loading by incorporating the concept of factional calculus. To describe the flow direction of granular soils under cyclic loading, a cyclic flow potential considering particle breakage is used. Test results of several types of granular soils are used to validate the model performance.

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Three-dimensional characterisation of particle size and shape for ballast

Cited by 78 publications

References 23 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

3D quantitative shape analysis on form, roundness, and compactness with μCT

Modelling long-term deformation of granular soils incorporating the concept of fractional calculus

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