Comparative Evaluation of Particle Movement in a Ballast Track Structure Stabilized with Biaxial and Multiaxial Geogrids

2017 ◽  
Vol 2607 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Shushu Liu ◽  
Hai Huang ◽  
Tong Qiu ◽  
Jayhyun Kwon
Keyword(s):  
Cyclic Loading ◽  
Comparative Evaluation ◽  
Vertical Displacement ◽  
Track Structure ◽  
Wireless Devices ◽  
Particle Movement ◽  
Railroad Track ◽  
Confining Effect ◽  
Ballast Track ◽  
Track Substructure

Geogrids usually are used in railroad track substructure for ballast reinforcement and stabilization over a weak subgrade. Different aperture shapes affect the confining effect on ballast particles due to the unique interlocking mechanism. To understand the effect of aperture shape on ballast particle movement and the associated interlocking mechanism, three types of ballast box tests were conducted: one without geogrid as a control, one with a layer of biaxial geogrid, and one with a layer of multiaxial geogrid. If a geogrid was included, the geogrid was placed 30 cm below the top of the ballast. A half-section of a railroad track structure consisting of two crossties, a rail, ballast, subballast, and subgrade was constructed in a ballast box. Four wireless devices known as SmartRocks were embedded under the rail seat and under the shoulder at the ballast–subballast and subballast–subgrade interfaces. Results indicate that the multiaxial geogrid significantly decreased accumulated vertical displacement in the ballast surface under cyclic loading and has the best potential for confining particle movement. The advantages of having a layer of multiaxial geogrid, including reducing particle movement, as well as decreasing vertical displacement of the ballast surface, are discussed.

Behavior of Geogrid-Reinforced Railroad Ballast Particles Under Different Loading Configurations During Initial Compaction Phase

2017 ◽  
Author(s):  
Shushu Liu ◽  
Hai Huang ◽  
Tong Qiu
Keyword(s):  
Vertical Displacement ◽  
Repeated Loading ◽  
Track Structure ◽  
Wireless Devices ◽  
Unbound Aggregates ◽  
Heavy Haul ◽  
Granular Particles ◽  
Heavy Haul Trains ◽  
Monitoring Behavior ◽  
Initial Compaction

A railroad ballast or subballast layer is composed of unbound granular particles. The ballast/subballast initial compaction phase occurs immediately the construction or maintenance of a track structure is finished. The particles are densified into a more compact state after certain load repetitions. Geogrids are commonly used in railroad construction for reinforcement and stabilization. Currently heavy haul trains are increasing the loads experienced by the substructural layers, which changes behavior of reinforced granular particles. This paper presents a series of ballast box tests to investigate the behavior of geogrid-reinforced unbound granular particles with rectangular (BX) and triangular (TX) shaped geogrids during the compaction phase. Three types of tests were conducted: one without geogrid as a control, one with a sheet of rectangular shaped geogrid, and the other one with a sheet of triangular shaped geogrid. The geogrid was placed at the interface between subballast and subgrade layers. A half section of a railroad track structure consisting of two crossties, a rail, ballast, subballast and subgrade was constructed in a ballast box. Four wireless devices - “SmartRocks”, embedded underneath the rail seat and underneath the shoulder at the interface of ballast-subballast, and subballast-subgrade layers, respectively, to monitor particle movement under cyclic loading. The behavior of the unbound aggregates in the three sections under two different loading configurations were compared. The results indicated that the inclusion of the geogrid significantly decreased accumulated vertical displacement on the ballast surface, ballast particle translation and rotation under a given repeated loading configuration. The results also demonstrated the effectiveness of the SmartRock device and its potential for monitoring behavior of ballast particles in the field.

scholarly journals Micro-mechanical investigation of railway ballast behavior under cyclic loading in a box test using DEM: effects of elastic layers and ballast types

2019 ◽  
Vol 21 (4) ◽  
Author(s):  
Nishant Kumar ◽  
Bettina Suhr ◽  
Stefan Marschnig ◽  
Peter Dietmaier ◽  
Christof Marte ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Early Stage ◽  
Damage Model ◽  
Simulation Models ◽  
Railway Track ◽  
Maintenance Cost ◽  
Particle Movement ◽  
Railway Ballast ◽  
Elastic Layers ◽  
The Impact

Abstract Ballasted tracks are the commonly used railway track systems with constant demands for reducing maintenance cost and improved performance. Elastic layers are increasingly used for improving ballasted tracks. In order to better understand the effects of elastic layers, physical understanding at the ballast particle level is crucial. Here, discrete element method (DEM) is used to investigate the effects of elastic layers – under sleeper pad ($$\text {USP}$$USP) at the sleeper/ballast interface and under ballast mat ($$\text {UBM}$$UBM) at the ballast/bottom interface – on micro-mechanical behavior of railway ballast. In the DEM model, the Conical Damage Model (CDM) is used for contact modelling. This model was calibrated in Suhr et al. (Granul Matter 20(4):70, 2018) for the simulation of two different types of ballast. The CDM model accounts for particle edge breakage, which is an important phenomenon especially at the early stage of a tamping cycle, and thus essential, when investigating the impact of elastic layers in the ballast bed. DEM results confirm that during cyclic loading, $$\text {USP}$$USP reduces the edge breakage at the sleeper/ballast interface. On the other hand, $$\text {UBM}$$UBM shows higher particle movement throughout the ballast bed. Both the edge breakage and particle movement in the ballast bed are found to influence the sleeper settlement. Micro-mechanical investigations show that the force chain in deeper regions of the ballast bed is less affected by $$\text {USP}$$USP for the two types of ballast. Conversely, dense lateral forces near to the box bottom were seen with $$\text {UBM}$$UBM. The findings are in good (qualitative) agreement with the experimental observations. Thus, DEM simulations can aid to better understand the micro-macro phenomena for railway ballast. This can help to improve the track components and track design based on simulation models taking into account the physical behavior of ballast. Graphical Abstract

The Stress and Stability Analyses of Railroad Tracks

1974 ◽  
Vol 41 (4) ◽  
pp. 841-848 ◽  
Author(s):  
A. D. Kerr
Keyword(s):  
The State ◽  
Track Structure ◽  
Railroad Track ◽  
Stability Analyses ◽  
Railroad Tracks ◽  
The Stability

The paper presents a survey of the state of knowledge in the fields of stress and stability determination of a railroad track. At first, the evolution of the railroad track structure is briefly summarized. This is followed by sections which discuss the development of the methods for the determination of stresses in the rails and ties, and the stability of the railroad track due to constrained thermal expansions.

ON ECONOMIC ASSESSMENT OF BALLASTLESS TRACK STRUCTURE EFFICIENCY

2017 ◽  
pp. 63-69
Author(s):  
Ludmila Andreyeva ◽  
Yevgeniy Svintsov ◽  
Yelena Tarasevich
Keyword(s):  
Comparative Analysis ◽  
Practical Importance ◽  
Economic Assessment ◽  
Track Structure ◽  
Advantages And Disadvantages ◽  
Ballastless Track ◽  
Study Results ◽  
Ballast Track ◽  
The Given

Objective: To describe the regulation of railroad traffic parameters in modern conditions, that lead to the necessity of putting into operation the new systems of track design, relevant for regulations in question. Methods: The method of matching, as well as the method of comparative analysis was applied in the study. Results: The advantages and disadvantages of ballastless track structure and conventional ballast track design were compared. The possibility of extensive application of ballastless track structure on modern railroads was analyzed. Practical importance: Ballastless track structure implementation will make it possible to solve practical tasks of using the given type of track design in transport construction.

The Minimum Longitudinal Horizontal Linear-Stiffness of Piers of Typical High-Speed Railway’s Layout of Turnout and Bridge

2011 ◽  
Vol 255-260 ◽  
pp. 3979-3983
Author(s):  
Zhe Liu ◽  
Wang Ping
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Element Model ◽  
Comprehensive Analysis ◽  
Track Structure ◽  
Continuous Beam ◽  
High Speed Railway ◽  
Railway Bridges ◽  
Ballast Track ◽  
Typical Layout

The values of longitudinal horizontal linear-stiffness of piers are very important parameters in the design of welded turnout on bridge and they can have a great impact on the force and displacement of the turnout. The layout form of turnout and bridge of welded turnout structure system on high-speed railway bridges are various, so the values of longitudinal horizontal linear-stiffness of piers have to be limited in order to insure the strength and stability of track structure on bridges and at the same time meet the requirement of comparative displacement of beam and rail, turnout proper and frog. To make the value-taking easy in the design process, a finite element model for welded turnout-bridge-platform is established in this paper, which is based on the principle of longitudinal interaction of welded turnout on bridges. Directing at three typical layout forms (No.18 single turnout+4×32m continuous beam, single crossover+6×32m continuous beam and typical throat point+4×32m continuous beam) of welded turnout and bridge on ballast track, a research of the relation between the force and displacement of turnout, and the values of longitudinal horizontal linear-stiffness of piers has been carried out. Based on the comprehensive analysis, minimal values of longitudinal horizontal linear-stiffness of piers which are suitable for these three kinds of layout forms, and the values are 1000,800 and 1600 kN/cm·double-line respectively.

scholarly journals Railway infrastructure in earthquake affected areas

2020 ◽  
Vol 72 (10) ◽  
pp. 905-921
Keyword(s):  
Track Structure ◽  
Safe Operation ◽  
Rail Vehicles ◽  
Railway Infrastructure ◽  
Longitudinal Resistance ◽  
Earthquake Action ◽  
Track Substructure ◽  
Seismic Impact ◽  
Small Deformations ◽  
Rail Traffic

In the case o seismic impact on rail infrastructure, even small deformations or damage to track structure can compromise safe operation of rail traffic. Damage can affect track substructure or permanent way of the track, but also the electrification system and safety-signalling devices. Ballast prism will suffer damage in case of greater intensity earthquakes, resulting in the reduction of lateral and longitudinal resistance of track structure. Earthquake action may also cause derailment of moving rail vehicles. Operation of rail vehicles also causes certain levels of vibrations, and so an analysis of subsequent effects of rail traffic.

Unsaturated Numerical Analysis Of A Railroad Track Substructure Considering Climate Data

2021 ◽  
pp. 100662
Author(s):  
G. Castro ◽  
J. Pires ◽  
R. Motta ◽  
L. Bernucci ◽  
F. Marinho ◽  
...  
Keyword(s):  
Numerical Analysis ◽  
Climate Data ◽  
Railroad Track ◽  
Track Substructure

scholarly journals Vertical cyclic loading response of shallow skirted foundation in soft normally consolidated clay

2019 ◽  
Vol 56 (4) ◽  
pp. 473-483 ◽  
Author(s):  
Dimitra Zografou ◽  
Susan Gourvenec ◽  
Conleth O’Loughlin
Keyword(s):  
Steady State ◽  
Cyclic Loading ◽  
Threshold Stress ◽  
Cyclic Load ◽  
Vertical Displacement ◽  
Offshore Structures ◽  
Kaolin Clay ◽  
Centrifuge Tests ◽  
Number Of Cycles ◽  
Mode A

Skirted foundations are a potential foundation solution for a range of offshore structures, including hydrocarbon and renewable energy platforms and subsea structures. Offshore foundations can be subject to cyclic loading from environmental, installation, and operational events affecting the geotechnical response. A series of centrifuge tests have been performed on a shallow skirted foundation on normally consolidated kaolin clay under a range of vertical cyclic load sequences to investigate the effect of tensile or compressive average stress, the magnitude of the applied stress, and the effect of cyclic loading of low magnitude followed by consolidation on the foundation response. Results are presented as vertical foundation displacements normalized by the foundation geometry and interpreted within the traditional shear-strain contour approach. The findings indicate that the average, rather than maximum, vertical stress defines the foundation vertical displacement response and failure mode, a threshold stress exists below which a steady state is maintained even at a high number of cycles, and geotechnical resistance increases as a result of low-level cyclic loading followed by consolidation.

Sign in / Sign up

Export Citation Format

Share Document