A Discrete Element Approach to Model Breakable Railway Ballast

2012 ◽  
Vol 7 (4) ◽  
Author(s):  
Christian Ergenzinger ◽  
Robert Seifried ◽  
Peter Eberhard
Keyword(s):  
Experimental Data ◽  
Element Model ◽  
Discrete Element ◽  
Quantitative Agreement ◽  
Discrete Element Model ◽  
Compression Tests ◽  
Railway Ballast ◽  
Element Approach ◽  
Strong Rock ◽  
Granular Solid

A discrete element approach to assess degradation processes in ballast beds is presented. Firstly, a discrete element model describing strength and failure of strong rock is introduced. For this purpose a granular solid is created by bonding of adjacent particles. A method to define angular ballast stones made from the granular solid is proposed. The strength of these stones is evaluated by compression between parallel platens. Comparing these results to published experimental data yields very good qualitative and reasonable quantitative agreement. Finally, the failure of aggregates of breakable stones is investigated by simulation of oedometric compression tests and indentation of a sleeper into a ballast bed.

scholarly journals Discrete element model for general polyhedra

2021 ◽  
Author(s):  
Alfredo Gay Neto ◽  
Peter Wriggers
Keyword(s):  
Frictional Contact ◽  
Virtual Work ◽  
Particle Surface ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Principle Of Virtual Work ◽  
Dynamics Model ◽  
Railway Ballast ◽  
Multibody Dynamics Model

AbstractWe present a version of the Discrete Element Method considering the particles as rigid polyhedra. The Principle of Virtual Work is employed as basis for a multibody dynamics model. Each particle surface is split into sub-regions, which are tracked for contact with other sub-regions of neighboring particles. Contact interactions are modeled pointwise, considering vertex-face, edge-edge, vertex-edge and vertex-vertex interactions. General polyhedra with triangular faces are considered as particles, permitting multiple pointwise interactions which are automatically detected along the model evolution. We propose a combined interface law composed of a penalty and a barrier approach, to fulfill the contact constraints. Numerical examples demonstrate that the model can handle normal and frictional contact effects in a robust manner. These include simulations of convex and non-convex particles, showing the potential of applicability to materials with complex shaped particles such as sand and railway ballast.

scholarly journals Microstructure-based modeling of snow mechanics: a discrete element approach

2015 ◽  
Vol 9 (2) ◽  
pp. 1425-1460 ◽  
Author(s):  
P. Hagenmuller ◽  
G. Chambon ◽  
M. Naaim
Keyword(s):  
Three Dimensional ◽  
Element Model ◽  
Discrete Element ◽  
Compression Tests ◽  
Confined Compression ◽  
Compression Behavior ◽  
Bonding System ◽  
Element Approach ◽  
Snow Mechanics ◽  
Snow Samples

Abstract. Rapid and large deformations of snow are mainly controlled by grain rearrangements, which occur through the failure of cohesive bonds and the creation of new contacts. We exploit a granular description of snow to develop a discrete element model based on the full three-dimensional microstructure captured by microtomography. The model assumes that snow is composed of rigid grains interacting through localized contacts accounting for cohesion and friction. The geometry of the grains and of the intergranular bonding system are explicitly defined from microtomographic data using geometrical criteria based on curvature and contiguity. Single grains are represented as rigid clumps of spheres. The model is applied to different snow samples subjected to confined compression tests. A detailed sensitivity analysis shows that artifacts introduced by the modeling approach and the influence of numerical parameters are limited compared to variations due to the geometry of the microstructure. The model shows that the compression behavior of snow is mainly controlled by the density of the samples, but that deviations from a pure density parameterization are not insignificant during the first phase of deformation. In particular, the model correctly predicts that, for a given density, faceted crystals are less resistant to compression than rounded grains or decomposed snow. For larger compression strains, no clear differences between snow types are observed.

Numerical Simulation of Sea Ice Compressional Strength with Discrete Element Model

2011 ◽  
Vol 268-270 ◽  
pp. 913-918
Author(s):  
Hai Li ◽  
Yu Liu ◽  
Xiang Jun Bi ◽  
Shun Ying Ji
Keyword(s):  
Experimental Data ◽  
Sea Ice ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Offshore Structure ◽  
Ice Load ◽  
Particle Bonding ◽  
Compressional Strength ◽  
Key Parameter

The compressional strength of sea ice is a key parameter to determine the interaction between ice cover and offshore structure. In this study, the discrete element model (DEM) with particle bonding function is adopted to model the sea ice compressional strength. The bonding strength is set as a function of the ice temperature and ice salinity, and their influences on sea ice compressional strength are observed. The simulated results are compared well with the physical experimental data. With the improvement of this DEM, the ice load and ice-induced vibration of offshore structure can be simulated.

scholarly journals Microstructure-based modeling of snow mechanics: a discrete element approach

2015 ◽  
Vol 9 (5) ◽  
pp. 1969-1982 ◽  
Author(s):  
P. Hagenmuller ◽  
G. Chambon ◽  
M. Naaim
Keyword(s):  
Large Deformations ◽  
Element Model ◽  
Discrete Element ◽  
Compression Tests ◽  
Confined Compression ◽  
Compression Behavior ◽  
Bonding System ◽  
Element Approach ◽  
Snow Mechanics ◽  
Snow Samples

Abstract. Rapid and large deformations of snow are mainly controlled by grain rearrangements, which occur through the failure of cohesive bonds and the creation of new contacts. We exploit a granular description of snow to develop a discrete element model based on the full 3-D microstructure captured by microtomography. The model assumes that snow is composed of rigid grains interacting through localized contacts accounting for cohesion and friction. The geometry of the grains and of the intergranular bonding system are explicitly defined from microtomographic data using geometrical criteria based on curvature and contiguity. Single grains are represented as rigid clumps of spheres. The model is applied to different snow samples subjected to confined compression tests. A detailed sensitivity analysis shows that artifacts introduced by the modeling approach and the influence of numerical parameters are limited compared to variations due to the geometry of the microstructure. The model shows that the compression behavior of snow is mainly controlled by the density of the samples, but that deviations from a pure density parameterization are not insignificant during the first phase of deformation. In particular, the model correctly predicts that, for a given density, faceted crystals are less resistant to compression than rounded grains or decomposed snow. For larger compression strains, no clear differences between snow types are observed.

scholarly journals Effect of the Soft and Hard Interbedded Layers of Bedrock on the Mechanical Characteristics of Stabilizing Piles

2020 ◽  
Vol 10 (14) ◽  
pp. 4760
Author(s):  
Manman Dong ◽  
Liangqing Wang ◽  
Babak Shahbodagh ◽  
Xi Du ◽  
Shan Deng ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mechanical Characteristics ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Maximum Displacement ◽  
Stabilizing Piles ◽  
Simulation Results ◽  
Dip Angle ◽  
Comparison With Experimental Data

In this paper, the mechanical characteristics of stabilizing piles embedded in layered bedrocks are studied both experimentally and numerically. The influence of soft and hard interbedded layers in the structure of the bedrock on the mechanical characteristics of stabilizing piles is particularly investigated. The discrete element method is used to numerically investigate the response of the stabilizing piles embedded in composite and inclined bedrocks. The simulation results and comparison with experimental data are presented to demonstrate the effectiveness and accuracy of the discrete element model. As the dip angle of the soft/hard interbedded bedrock layers increases from 0° to 45°, it is observed that the displacement of the embedded section of the stabilizing pile increases and reaches the maximum displacement at 45°. In the range of 45° to 75°, the influence of the dip angle of the layered bedrock on the displacement of the embedded section of the pile is gradually reduced.

scholarly journals Impact of Ballast Fouling on the Mechanical Properties of Railway Ballast: Insights from Discrete Element Analysis

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1331
Author(s):  
Luyu Wang ◽  
Mohamed Meguid ◽  
Hani S. Mitri
Keyword(s):  
Shear Strength ◽  
Mechanical Response ◽  
Fine Particles ◽  
Element Model ◽  
Discrete Element ◽  
Shear Loading ◽  
Discrete Element Model ◽  
Railway Ballast ◽  
Fouled Ballast ◽  
Interparticle Friction

Ballast fouling is a major factor that contributes to the reduction of shear strength of railway ballast, which can further affect the stability of railway supporting structure. The major sources of ballast fouling include infiltration of foreign fines into the ballast material and ballast degradation induced by train movement on the supported tracks. In this paper, a discrete element model is developed and used to simulate the shear stress–strain response of fouled ballast assembly subjected to direct shear loading. A simplified computational approach is then proposed to model the induced ballast fouling and capture the mechanical response of the ballast at various levels of contamination. The approach is based on the assumption that fine particles comprising the fouling material will not only change the interparticle friction angle, but also the contact stiffness between the ballast particles. Therefore, both the interparticle friction coefficient and effective modulus are adjusted based on a fouled ballast model that is validated using experimental results. The effect of ballast degradation is also investigated by gradually changing the particle size distribution of the ballast assembly in the discrete element model to account for the increased range of particle sizes. Using the developed model, the effect of ballast degradation on the shear strength is then evaluated. Conclusions are made to highlight the suitability of these approximate approaches in efficiently modeling ballast assemblies under shear loading conditions.

scholarly journals A Quantitative Discrete Element Model to Investigate Sub-Surface Damage due to Surface Polishing

2012 ◽  
Author(s):  
Damien André ◽  
Ivan Iordanoff ◽  
Jean-luc Charles ◽  
Jérôme Néauport
Keyword(s):  
Experimental Data ◽  
Silica Glass ◽  
Surface Damage ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Continuous Part ◽  
Surface Polishing ◽  
Quantitative Results ◽  
Good Agreement

This work is a continuation of a previous study that investigated sub-surface damage in silica glass due to surface polishing. In this previous study, discrete element models have shown qualitatively good agreement with experiments. The presented work propose a model allowing quantitative results by focusing on the continuous part of the problem. Special attemption was given to the discrete element model of silica glass considered as perfectly isotropic, elastic and brittle. To validate this approach, numerical results are compared to experimental data from literature.

A discrete element model to describe failure of strong rock in uniaxial compression

2010 ◽  
Vol 13 (4) ◽  
pp. 341-364 ◽  
Author(s):  
Christian Ergenzinger ◽  
Robert Seifried ◽  
Peter Eberhard
Keyword(s):  
Uniaxial Compression ◽  
Element Model ◽  
Discrete Element ◽  
Discrete Element Model ◽  
Strong Rock
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