All Outputs (43)

Micro-mechanical behavior of stone-blowing in ballast maintenance using DEM-CFD coupling method (2024)
Journal Article

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.

Micro mechanics of the critical state line at high stresses (2018)
Journal Article

A critical state line is presented for a crushable numerical soil, which is parallel to the isotropic normal compression line. A previous theory for the normal compression line, which correctly predicts the slope as a function of the size-effect on p... Read More about Micro mechanics of the critical state line at high stresses.

On the micro mechanics of yielding and hardening of crushable granular soils (2018)
Journal Article

Stress path tests are used to investigate the yield surface of a crushable numerical soil. Triaxial samples with isotropic and anisotropic stress histories are examined to determine the nature of the yield surface and to establish what governs yield.... Read More about On the micro mechanics of yielding and hardening of crushable granular soils.