All Outputs (45)

Optimizing ballast reinforcement: comparative analysis of single and double-layer geogrid configurations through pullout tests (2025)
Journal Article
Chen, C., Lin, X.-D., McDowell, G., Zhang, L., Rui, R., & Duan, Y.-D. (2025). Optimizing ballast reinforcement: comparative analysis of single and double-layer geogrid configurations through pullout tests. International Journal of Geosynthetics and Ground Engineering, 11(4), Article 33. https://doi.org/10.1007/s40891-025-00636-9

This study investigates the reinforcement mechanism of double-layer geogrid-reinforced ballast through a series of single-layer and double-layer pullout tests. The effects of geogrid layers, aperture size, and reinforcement depth were analyzed in det... Read More about Optimizing ballast reinforcement: comparative analysis of single and double-layer geogrid configurations through pullout tests.

Numerical study on ballast disturbance and maintenance performance of tamping and stone-blowing (2025)
Journal Article
Chen, C., Li, P.-Y., McDowell, G., Zhang, L., & Rao, W.-J. (2025). Numerical study on ballast disturbance and maintenance performance of tamping and stone-blowing. Construction and Building Materials, 460, Article 139837. https://doi.org/10.1016/j.conbuildmat.2024.139837

Ballasted trackbeds are prone to settlement and degradation under long-term train loads, effective and timely maintenance is crucial for extending the lifespan of trackbeds and ensuring the safety of railway operations. Ballast maintenance, such as t... Read More about Numerical study on ballast disturbance and maintenance performance of tamping and stone-blowing.

Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method (2024)
Journal Article
Chen, C., Rao, W., Zhang, L., McDowell, G., & Li, P. (2024). Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method. Transportation Geotechnics, 46, Article 101263. https://doi.org/10.1016/j.trgeo.2024.101263

Stone-blowing restores the track geometry by blowing small crushed stones into the bottom of the sleeper, extending the maintenance period. In this study, ballast and filling stones were modelled using discrete element method (DEM), while the air blo... Read More about Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method.

A study of membrane correction accounting for both curvature and tension in DEM simulations of triaxial tests of sand and ballast with two alternative flexible membrane models (2024)
Journal Article
Tolomeo, M., & McDowell, G. R. (2024). A study of membrane correction accounting for both curvature and tension in DEM simulations of triaxial tests of sand and ballast with two alternative flexible membrane models. Granular Matter, 26(2), Article 47. https://doi.org/10.1007/s10035-024-01419-1

In DEM simulations of triaxial tests, modelling a flexible lateral membrane is crucial and challenging. It is essential for the correct application of a uniform lateral pressure and for an accurate measurement of sample volume. Here, we introduce a m... Read More about A study of membrane correction accounting for both curvature and tension in DEM simulations of triaxial tests of sand and ballast with two alternative flexible membrane models.

Modelling the mechanical behaviour of clay using particle-scale simulations (2024)
Journal Article
de Bono, J., & McDowell, G. (2024). Modelling the mechanical behaviour of clay using particle-scale simulations. Granular Matter, 26(2), Article 29. https://doi.org/10.1007/s10035-024-01401-x

This paper demonstrates the latest developments in particle-scale modelling of a clay. It shows that by creating an initial sample of platelets featuring aggregated stacks, excellent macroscopic behaviour is achieved. This approach is justified by ex... Read More about Modelling the mechanical behaviour of clay using particle-scale simulations.

A particle-scale analysis of unload-reload hysteresis for normally consolidated kaolin (2023)
Journal Article
de Bono, J., & McDowell, G. (2023). A particle-scale analysis of unload-reload hysteresis for normally consolidated kaolin. Applied Clay Science, 246, Article 107190. https://doi.org/10.1016/j.clay.2023.107190

The mechanical behaviour of sands and clays subject to “normal” (plastic) compression are very similar, albeit at different stress levels, despite the differences in inter-particle interactions (Hertzian normal contact forces or similar for sand) and... Read More about A particle-scale analysis of unload-reload hysteresis for normally consolidated kaolin.

Particle-scale simulations of the compression and shearing of kaolin clay (2023)
Journal Article
de Bono, J. P., & McDowell, G. R. (2023). Particle-scale simulations of the compression and shearing of kaolin clay. Géotechnique, 74(13), 1729-1741. https://doi.org/10.1680/jgeot.22.00423

This paper presents a new model for particle-scale simulations of clay. Using the discrete-element method, featuring realistically shaped platelets with separate interactions between the various platelet surfaces, simulations of isotropic normal comp... Read More about Particle-scale simulations of the compression and shearing of kaolin clay.

DEM study of an “avatar” railway ballast with real particle shape, fabric and contact mechanics (2023)
Journal Article
Tolomeo, M., & McDowell, G. R. (2023). DEM study of an “avatar” railway ballast with real particle shape, fabric and contact mechanics. Granular Matter, 25(2), Article 32. https://doi.org/10.1007/s10035-023-01322-1

In this paper we show DEM simulations of static and cyclic large triaxial tests on a sample of railway ballast. The sample is reconstructed from X-Ray tomography images of an untested laboratory sample, recovered by impregnation with an epoxy resin.... Read More about DEM study of an “avatar” railway ballast with real particle shape, fabric and contact mechanics.

Simulating multifaceted interactions between kaolinite platelets (2022)
Journal Article
de Bono, J., & McDowell, G. (2023). Simulating multifaceted interactions between kaolinite platelets. Powder Technology, 413, Article 118062. https://doi.org/10.1016/j.powtec.2022.118062

It is well known that kaolinite platelets readily aggregate into ‘stacks’, having face-to-face contact. The traditional view of kaolin has been that the platelet faces are negatively charged and the edges are positively charged in an acidic environme... Read More about Simulating multifaceted interactions between kaolinite platelets.

Implementation of real contact behaviour in the DEM modelling of triaxial tests on railway ballast (2022)
Journal Article
Tolomeo, M., & McDowell, G. R. (2022). Implementation of real contact behaviour in the DEM modelling of triaxial tests on railway ballast. Powder Technology, 412, Article 118021. https://doi.org/10.1016/j.powtec.2022.118021

In the Discrete Element modelling of soils, the micromechanical behaviour at contacts has often been considered to have a minor influence on the macromechanical response, leaving basic theoretical models (e.g., Hertz) to describe the contact response... Read More about Implementation of real contact behaviour in the DEM modelling of triaxial tests on railway ballast.

Modelling real particle shape in DEM: a comparison of two methods with application to railway ballast (2022)
Journal Article
Tolomeo, M., & McDowell, G. R. (2022). Modelling real particle shape in DEM: a comparison of two methods with application to railway ballast. International Journal of Rock Mechanics and Mining Sciences, 159, Article 105221. https://doi.org/10.1016/j.ijrmms.2022.105221

Two different methods for the modelling of real particle shape in 3D DEM simulations are assessed in this paper. The first method uses overlapping spheres (clumps), while the second uses a block defined as a closed and convex polyhedron. The two meth... Read More about Modelling real particle shape in DEM: a comparison of two methods with application to railway ballast.

Discrete element modelling of normal compression of clay (2022)
Journal Article
de Bono, J. P., & McDowell, G. R. (2022). Discrete element modelling of normal compression of clay. Journal of the Mechanics and Physics of Solids, 162, Article 104847. https://doi.org/10.1016/j.jmps.2022.104847

The discrete element method (DEM) has only rarely been used to simulate clay, due to difficulties in modelling clay particle shape and capturing the various particle interactions. This paper presents a new approach to simulate clay in three dimension... Read More about Discrete element modelling of normal compression of clay.

Some important aspects of modelling clay platelet interactions using DEM (2021)
Journal Article
de Bono, J. P., & McDowell, G. R. (2022). Some important aspects of modelling clay platelet interactions using DEM. Powder Technology, 398, Article 117056. https://doi.org/10.1016/j.powtec.2021.117056

The discrete element method (DEM) is a popular tool for simulating soils, however it has rarely been used for modelling clays. This is despite the behaviour of clays being much less well understood compared to sands. This paper aims to increase the u... Read More about Some important aspects of modelling clay platelet interactions using DEM.

A new time-delayed periodic boundary condition for discrete element modelling of railway track under moving wheel loads (2021)
Journal Article
Li, H., McDowell, G., & De Bono, J. (2021). A new time-delayed periodic boundary condition for discrete element modelling of railway track under moving wheel loads. Granular Matter, 23(4), Article 75. https://doi.org/10.1007/s10035-021-01123-4

A new time-delayed periodic boundary condition (PBC) has been proposed for discrete element modelling (DEM) of periodic structures subject to moving loads such as railway track based on a box test which is normally used as an element testing model. T... Read More about A new time-delayed periodic boundary condition for discrete element modelling of railway track under moving wheel loads.

Relating Hydraulic Conductivity to Particle Size Using DEM (2020)
Journal Article
McDowell, G., & de Bono, J. (2021). Relating Hydraulic Conductivity to Particle Size Using DEM. International Journal of Geomechanics, 21(1), Article 0602003. https://doi.org/10.1061/%28asce%29gm.1943-5622.0001670

For over 100 years it has been accepted that the permeability or hydraulic conductivity of a soil is controlled by the size of pores through which the fluid flows, and that this pore size should be a function of particle sizes. All well-known formula... Read More about Relating Hydraulic Conductivity to Particle Size Using DEM.

Discrete element modelling of two-layered ballast in a box test (2020)
Journal Article
Li, H., & Mcdowell, G. (2020). Discrete element modelling of two-layered ballast in a box test. Granular Matter, 22, Article 76. https://doi.org/10.1007/s10035-020-01046-6

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 e... Read More about Discrete element modelling of two-layered ballast in a box test.

A new abrasive wear model for railway ballast (2020)
Journal Article
De Bono, J., Li, H., & McDowell, G. (2020). A new abrasive wear model for railway ballast. Soils and Foundations, 60(3), 714-721. https://doi.org/10.1016/j.sandf.2020.05.001

A new method to model the abrasion of granular particles using the discrete element method is demonstrated in this paper. This new, simple method is based on a classical theory of abrasive wear, relating the volume of solid lost to the frictional wor... Read More about A new abrasive wear model for railway ballast.

The effects of particle shape on the yielding behaviour of crushable sand (2020)
Journal Article
De Bono, J., & Mcdowell, G. (2020). The effects of particle shape on the yielding behaviour of crushable sand. Soils and Foundations, 60(2), 520-532. https://doi.org/10.1016/j.sandf.2020.04.001

Discrete element method simulations are used to investigate the effects of particle shape on the plastic behaviour of sand. This is achieved by using four different shapes of crushable particles. The behaviours of the different particles when subject... Read More about The effects of particle shape on the yielding behaviour of crushable sand.

On the packing and crushing of granular materials (2018)
Journal Article
de Bono, J. P., & McDowell, G. R. (2020). On the packing and crushing of granular materials. International Journal of Solids and Structures, 187, 133-140. https://doi.org/10.1016/j.ijsolstr.2018.07.011

This paper is a study of the dependence of the volume of voids in a granular material on the particle size distribution. It has previously been proposed that the volume of voids is proportional to the volume of the smallest particles. In a particle s... Read More about On the packing and crushing of granular materials.

Discreet element modeling of under sleeper pads using a box test (2018)
Journal Article
Li, H., & McDowell, G. R. (2018). Discreet element modeling of under sleeper pads using a box test. Granular Matter, 20(2), Article 26. https://doi.org/10.1007/s10035-018-0795-0

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 mod... Read More about Discreet element modeling of under sleeper pads using a box test.