Evaluation of Ballast Behavior under Different Tie Support Conditions using Discrete Element Modeling

This paper presents findings of a railroad ballast study using the discrete element method (DEM) focused on mesoscale performance modeling of ballast layer under different tie support conditions. The simulation assembles ballast gradation that met the requirements of both American Railway Engineering and Maintenance-of-Way Association (AREMA) No. 3 and No. 4A specifications with polyhedral particle shapes created similar to the field-collected ballast samples. A full-track model was generated as a basic model, on which five different support conditions were studied in the DEM simulation. Static rail seat loads of 10 kips (44.5 kN) were applied until the DEM model became stable. The pressure distribution along the tie-ballast interface predicted by DEM simulations was in good agreement with previously published results backcalculated from laboratory testing. Static rail seat loads of 20 kips (89 kN) were then applied in the calibrated DEM model to evaluate in-track performance. Results from the validated full-track DEM simulations indicated that only a small portion of ballast particles participated in load distribution under static loading. Particles on the shoulders and particles in the areas with poor support conditions often experience no or very low contact forces. Load transfer mechanisms investigated through a contact force network varied greatly among different support conditions: lack of rail seat support, full support, and lack of center support had wider force distribution angles than the high center binding and severe center binding conditions. The severe center binding scenario was found to be the most critical support condition in terms of causing the highest tie-ballast contact pressure exceeding 30% of the AREMA allowable pressure.

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Implications of Field Loading Patterns on Different Tie Support Conditions using Discrete Element Modeling: Dynamic Responses

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198118821936 ◽

2019 ◽

Vol 2673 (2) ◽

pp. 509-520 ◽

Cited By ~ 3

Author(s):

Bin Feng ◽

Wenting Hou ◽

Erol Tutumluer

Keyword(s):

Dynamic Load ◽

Load Transfer ◽

Discrete Element ◽

Dynamic Responses ◽

Discrete Element Modeling ◽

Particle Movement ◽

Passenger Car ◽

Loading Patterns ◽

Support Conditions ◽

High Center

With increasing demands for rail passenger and freight operations, sharing a line or track is an economical solution if operational efficiency and track reliability challenges can be accommodated properly. This paper presents findings of ballast layer dynamic responses related to four different freight and passenger car loading patterns studied for four different tie support conditions using the Discrete Element Method (DEM). With the DEM model setup being identical for each support condition, ballast particle contact force networks were visualized first under one dynamic load cycle. Certain load transfer chains were observed associated with all four support conditions. Next, crosstie dynamic velocities were analyzed for all sixteen combinations of the different loading patterns and support conditions. The freight car loads traveling at 50 mph could induce higher crosstie vibration velocities than the lighter passenger car loads traveling at 110 mph and 150 mph in three support conditions: lack of center support, high center binding, and lack of rail seat support. Dynamic movements of ballast particles were visualized in velocity vector plots based on their initial and final centroid coordinates. Results reveal that for the same axle load, higher speeds will cause larger ballast particle movements. However, with higher load magnitudes, larger particle movements can be observed even at lower speeds. Generally, high center binding results in the smallest particle movement while lack of center support presents the largest particle movement. Dynamic load responses of the ballast layer simulations provide insights into evaluating and optimizing tracks to be shared by passenger and freight trains.

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Discrete Element Model Calibration Using Multi-Responses and Simulation of Corn Flow in a Commercial Grain Auger

Transactions of the ASABE ◽

10.13031/trans.12742 ◽

2018 ◽

Vol 61 (5) ◽

pp. 1743-1755 ◽

Cited By ~ 2

Author(s):

Mehari Z. Tekeste ◽

Mohammad Mousaviraad ◽

Kurt A. Rosentrater

Keyword(s):

Optimization Technique ◽

Particle Interaction ◽

Discrete Element ◽

Angle Of Repose ◽

Quantitative Prediction ◽

Discrete Element Modeling ◽

Latin Hypercube Design ◽

Linear Regression Models ◽

Element Modeling ◽

Dem Simulations

Abstract. Grain augers are primary grain conveying equipment in agriculture. Quantitative prediction of dynamic grain flow in grain augers using discrete element modeling (DEM) has potential to support simulation-based engineering design of grain handling equipment. The objective of this study was to develop a DEM corn model using a multi-response calibration methodology and validation of combine-harvested corn flow in a commercial grain auger. Using a Latin hypercube design of experiment (DOE) sampling from four particle interaction DEM parameters values, 27 DEM simulations were generated for four DEM corn shape approximations (1-sphere, 2-spheres, 5-spheres, and 13-spheres) to create virtual DEM experiments of bucket-discharged and anchor-lifted angle of repose (AOR) tests. A surface meta-model was developed using the DEM interaction parameters as predictor variables, and normalized AOR expressed as a mean square error (MSE), i.e., the sum of square differences between DEM simulations and laboratory-measured AOR. Analysis of the MSE percentiles with lower error differences between DEM simulations and laboratory AOR and the computational effort required per simulation (h per simulation) showed that the 2-spheres DEM model had better performance than the 1-sphere, 5-spheres, and 13-spheres models. Using the best stepwise linear regression models of bucket AOR MSE (R2 of 0.9423 and RMSE of 94.56) and anchor AOR MSE (R2 of 0.5412 and RMSE of 78.02) and a surface profiler optimization technique, an optimized 2-spheres DEM corn model was generated. The DEM predicted AOR with relative errors of 8.5% for bucket AOR and 7.0% for anchor AOR. A DEM grain auger simulation used as a validation step also showed good agreement with the laboratory-measured steady-state mass flow rate (kg s-1) and static AOR (degrees) of corn piled on a flat surface, with DEM prediction relative error ranging from 2.8% to 9.6% and from 8.55% to 1.26%, respectively. Keywords: Corn, DEM, Discharge angle of repose, Discrete element modeling, Grain auger, Lift angle of repose.

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Ballast Support Condition Affecting Crosstie Performance Investigated Through Discrete Element Method

2018 Joint Rail Conference ◽

10.1115/jrc2018-6258 ◽

2018 ◽

Author(s):

Wenting Hou ◽

Bin Feng ◽

Wei Li ◽

Erol Tutumluer

Keyword(s):

Discrete Element Method ◽

Discrete Element ◽

Force Transmission ◽

Support Condition ◽

Normal Stress Distribution ◽

Binding Condition ◽

Polyhedral Particles ◽

Dem Simulations ◽

Support Conditions ◽

Element Method

This paper reports on the ballast layer mesoscale behavior, tie-ballast interaction, and ballast-subgrade interaction under five crosstie support conditions, namely full support, lack of rail seat support, lack of center support, high center binding, and severe center binding condition. Discrete Element Method, an effective technique to study particulate natured unbound aggregate materials, i.e., ballast, was adopted in this study. The DEM simulations included one-tie spacing geometry, approximately 11,000 polyhedral particles. The ballast gradation used in DEM models was according to the AREMA No. 3 and No. 4A specifications. The shape properties of ballast particles in DEM models was consistent with field collected samples. The pressure distributions along tie-ballast interface under rail seat load of 10-kips predicted by DEM simulations were in good agreement with the results backcalculated from laboratory tests, which validated the DEM models. Next, DEM simulations considered rail seat loads of 20-kips and 25-kips. The predicted results indicated that support condition is a key factor for predicting normal stress distribution and force transmission within ballast layer. Ballast particles in shoulders and areas with poor support indicated low or negligible contact stresses. Extremely high normal stresses observed in some support conditions often exceeded single particle crushing load limit and thus would cause ballast particle breakage and layer degradation under repeated loading. Further, the tie-ballast pressure captured in some scenarios could be higher than allowable maximum pressure of 85-psi under concrete tie in AREMA standard. Finally, the pressure at bottom of the ballast layer obtained from the DEM simulations were compared with top of subgrade pressure calculated from analytical/empirical equations such as Talbot equation and AREMA manual.

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Laboratory Development and Testing of “SmartRock” for Railroad Ballast Using Discrete Element Modeling

2015 Joint Rail Conference ◽

10.1115/jrc2015-5694 ◽

2015 ◽

Cited By ~ 7

Author(s):

Shushu Liu ◽

Hai Huang ◽

Tong Qiu

Keyword(s):

Laboratory Tests ◽

Imaging Techniques ◽

Laboratory Data ◽

Discrete Element ◽

Contact Forces ◽

Repeated Loading ◽

Discrete Element Modeling ◽

Element Modeling ◽

Increased Risk ◽

Railroad Applications

Ballast aggregate settlement is generally a result of consolidation or rearrangment of ballast particles in the area underneath crossties. Excessive settlement negatively impacts track performance, resulting in increased risk of train derailment. The purpose of this paper is to compare two methods to evaluate ballast aggregate settlement with repeated loading in railroad: discrete element modeling and laboratory tests using “SmartRock”. In this study, ballast aggregates are considered as uniformly graded, angular shaped with crushed faces. For the discrete element modeling, digital imaging techniques are utilized to create the ballast aggregates. Aggregate settlement in railroad ballast and the effect of aggregate shape on the dynamic response of ballast are evaluated through the discrete element simulations. A wireless device, “SmartRock” is developed to study the relationship between individual ballast particle behavior and overall ballast performance. It has a shell of a typical ballast particle shape with force cells attached on the surface and embedded with a tri-axial gyroscope, a tri-axial accelerometer, and a tri-axial magnetometer. The device can move under train traffic like a real ballast particle and record inter-particle contact forces and particle motion in real time. For the laboratory tests, a model-scale track section is constructed and subjected to repeated loading similar to train traffic. The developed “SmartRock” are embedded below rail seats and in the track shoulders. The laboratory data using “SmartRock” can be compared with results from the discrete element modeling in the future. These comparisons will validate the discrete element modeling procedure as a means to analyze railroad ballast aggregate behavior and the potential of “SmartRock” in railroad applications.

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Numerical investigation of force transmission in granular media using discrete element method

Vietnam Journal of Mechanics ◽

10.15625/0866-7136/14787 ◽

2020 ◽

Cited By ~ 2

Author(s):

Thong Chung Nguyen ◽

Lu Minh Le ◽

Hai-Bang Ly ◽

Tien-Thinh Le

Keyword(s):

Discrete Element Method ◽

Granular Media ◽

Mechanical Response ◽

Discrete Element ◽

Contact Forces ◽

Force Transmission ◽

Uniform Compression ◽

Applied Loading ◽

Dem Model ◽

Element Method

In this paper, a numerical Discrete Element Method (DEM) model was calibrated to investigate the transmission of force in granular media. To this aim, DEM simulation was performed for reproducing the behavior of a given granular material under uniform compression. The DEM model was validated by comparing the obtained shear stress/normal stress ratio with results published in the available literature. The network of contact forces was then computed, showing the arrangement of the material microstructure under applied loading. The number and distribution of the contacts force were also examined statistically, showing that the macroscopic behavior of the granular medium highly depended on the force chain network. The DEM model could be useful in exploring the mechanical response of granular materials under different loadings and boundary conditions.

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Applications of Discrete Element Method in the Research of Agricultural Machinery: A Review

Agriculture ◽

10.3390/agriculture11050425 ◽

2021 ◽

Vol 11 (5) ◽

pp. 425

Author(s):

Hongbo Zhao ◽

Yuxiang Huang ◽

Zhengdao Liu ◽

Wenzheng Liu ◽

Zhiqi Zheng

Keyword(s):

Discrete Element Method ◽

Discrete Element ◽

Agricultural Machinery ◽

Design And Optimization ◽

Design Of Agricultural Machinery ◽

Agricultural Materials ◽

Operational Processes ◽

Dem Model ◽

Agricultural Machines ◽

Element Method

As a promising and convenient numerical calculation approach, the discrete element method (DEM) has been increasingly adopted in the research of agricultural machinery. DEM is capable of monitoring and recording the dynamic and mechanical behavior of agricultural materials in the operational process of agricultural machinery, from both a macro-perspective and micro-perspective; which has been a tremendous help for the design and optimization of agricultural machines and their components. This paper reviewed the application research status of DEM in two aspects: First is the DEM model establishment of common agricultural materials such as soil, crop seed, and straw, etc. The other is the simulation of typical operational processes of agricultural machines or their components, such as rotary tillage, subsoiling, soil compaction, furrow opening, seed and fertilizer metering, crop harvesting, and so on. Finally, we evaluate the development prospects of the application of research on the DEM in agricultural machinery, and look forward to promoting its application in the field of the optimization and design of agricultural machinery.

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An Energy-Based Discrete Element Modeling Method Coupled with Time-Series Analysis for Investigating Deformations and Failures of Jointed Rock Slopes

Applied Sciences ◽

10.3390/app11125447 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5447

Author(s):

Xiaona Zhang ◽

Gang Mei ◽

Ning Xi ◽

Ziyang Liu ◽

Ruoshen Lin

Keyword(s):

Time Series ◽

Iterative Process ◽

Discrete Element ◽

Jointed Rock ◽

Modeling Method ◽

Discrete Element Modeling ◽

Rock Slopes ◽

Sliding Surface ◽

Element Modeling ◽

Displacement Based

The discrete element method (DEM) can be effectively used in investigations of the deformations and failures of jointed rock slopes. However, when to appropriately terminate the DEM iterative process is not clear. Recently, a displacement-based discrete element modeling method for jointed rock slopes was proposed to determine when the DEM iterative process is terminated, and it considers displacements that come from rock blocks located near the potential sliding surface that needs to be determined before the DEM modeling. In this paper, an energy-based discrete element modeling method combined with time-series analysis is proposed to investigate the deformations and failures of jointed rock slopes. The proposed method defines an energy-based criterion to determine when to terminate the DEM iterative process in analyzing the deformations and failures of jointed rock slopes. The novelty of the proposed energy-based method is that, it is more applicable than the displacement-based method because it does not need to determine the position of the potential sliding surface before DEM modeling. The proposed energy-based method is a generalized form of the displacement-based discrete element modeling method, and the proposed method considers not only the displacement of each block but also the weight of each block. Moreover, the computational cost of the proposed method is approximately the same as that of the displacement-based discrete element modeling method. To validate that the proposed energy-based method is effective, the proposed method is used to analyze a simple jointed rock slope; the result is compared to that achieved by using the displacement-based method, and the comparative results are basically consistent. The proposed energy-based method can be commonly used to analyze the deformations and failures of general rock slopes where it is difficult to determine the obvious potential sliding surface.

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A new time-delayed periodic boundary condition for discrete element modelling of railway track under moving wheel loads

Granular Matter ◽

10.1007/s10035-021-01123-4 ◽

2021 ◽

Vol 23 (4) ◽

Author(s):

Huiqi Li ◽

Glenn McDowell ◽

John de Bono

Keyword(s):

Boundary Condition ◽

Periodic Boundary Condition ◽

Periodic Boundary ◽

Discrete Element ◽

Contact Forces ◽

Railway Track ◽

Discrete Element Modelling ◽

Fixed Boundary ◽

Element Modelling ◽

New Time

Abstract 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. The new proposed time-delayed PBC is approached by predicting forces acting on ghost particles with the consideration of different loading phases for adjacent sleepers whereas a normal PBC simply gives the ghost particles the same contact forces as the original particles. By comparing the sleeper in a single sleeper test with a fixed boundary, a normal periodic boundary and the newly proposed time-delayed PBC (TDPBC), the new TDPBC was found to produce the closest settlement to that of the middle sleeper in a three-sleeper test which was assumed to be free of boundary effects. It appears that the new TDPBC can eliminate the boundary effect more effectively than either a fixed boundary or a normal periodic cell. Graphic abstract

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Simple Design Solution for Harsh Operating Conditions: Redesign of Conveyor Transfer Station with Reverse Engineering and DEM Simulations

Energies ◽

10.3390/en14134008 ◽

2021 ◽

Vol 14 (13) ◽

pp. 4008

Author(s):

Błażej Doroszuk ◽

Robert Król ◽

Jarosław Wajs

Keyword(s):

Reverse Engineering ◽

Laser Scanning ◽

Design For Manufacturing ◽

Operating Conditions ◽

Design Solution ◽

Dem Simulations ◽

Transfer Station ◽

Transfer Stations ◽

Dem Model ◽

Current Operating

This paper addresses the problem of conveyor transfer station design in harsh operating conditions, aiming to identify and eliminate a failure phenomenon which interrupts aggregate supply. The analyzed transfer station is located in a Polish granite quarry. The study employs laser scanning and reverse engineering methods to map the existing transfer station and its geometry. Next, a discrete element method (DEM) model of granite aggregate has been created and used for simulating current operating conditions. The arch formation has been identified as the main reason for breakdowns. Alternative design solutions for transfer stations were tested in DEM simulations. The most uncomplicated design for manufacturing incorporated an impact plate, and a straight chute has been selected as the best solution. The study also involved identifying areas of the new station most exposed to wear phenomena. A new transfer point was implemented in the quarry and resolved the problem of blockages.

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