Slab Track Research Articles

Numerical investigation of porous composite honeycomb track slab under point load

Traditional railway infrastructures include ballasted beds and concrete slab tracks. The additive manufacturing technology enables the application of porous structures in railway infrastructures. In this article, two types of porous supporting layers acting as the track supporting layer are designed. The nonlinear FEM simulations of composite porous track infrastructures are carried out to study the mechanical performance of the porous honeycomb track slab under point loads using nonlinear material properties. The track performance, including deflection and acceleration, of different track components, are compared with a conventional ballasted track to evaluate the feasibility of the 3D printed structures. This study can help the development of 3D printed porous composite honeycomb structures in railway engineering.

New Floating Slab Track Isolator for Vibration Reduction Using Particle Damping Vibration Absorption and Bandgap Vibration Resistance

New Floating Slab Track Isolator for Vibration Reduction Using Particle Damping Vibration Absorption and Bandgap Vibration Resistance

Influence of Uneven Frost Heave of Subgrade on Deformation and Damage of Crts-Iii Slab Track

Influence of Uneven Frost Heave of Subgrade on Deformation and Damage of Crts-Iii Slab Track

Study on Two Parameters of Repair Materials for Interface Crack of Railway Slab Track Based on an Improved Cohesive Zone Model

Study on Two Parameters of Repair Materials for Interface Crack of Railway Slab Track Based on an Improved Cohesive Zone Model

Effects of Mortar Void of CRTS Ⅱ Slab Track on the Dynamic Performances of Vehicle-track System

Effects of Mortar Void of CRTS Ⅱ Slab Track on the Dynamic Performances of Vehicle-track System

Vertical Nonlinear Temperature Gradient and Temperature Load Mode of Ballastless Track in China

In the process of heat exchange with the external environment, the internal temperature of ballastless track structure presents a nonlinear distribution. The vertical temperature gradient will cause repeated warping and deformation of track slab, resulting in mortar layer separation, which will affect driving comfort and track durability. The traditional temperature field analysis method of concrete structure based on thermodynamics has the disadvantages of too many assumptions, difficult parameter selection and too much calculation of energy consumption. In this paper, based on the finite element software ANSYS, the heat exchange was transformed into the boundary condition of heat flux, which was applied to the thermodynamic analysis model to study the nonlinear temperature distribution law of ballastless track. The accuracy of the analysis method was verified by the measured data. On this basis, the regional distribution law of temperature gradient of ballastless track under different geographical coordinates and climatic conditions was studied. By adding a regional adjustment coefficient, the vertical temperature load model of ballastless track suitable for typical areas in China was proposed. The proposed temperature load model makes up for the lack of refinement of climate division and temperature load model in relevant specifications, and has strong engineering application and popularization value.

Fatigue Behaviors of Interface between Ballastless Track Slab and Self-Compacting Concrete: A Novel Fatigue Cohesive Model for the Analysis of Track Structure

Fatigue Behaviors of Interface between Ballastless Track Slab and Self-Compacting Concrete: A Novel Fatigue Cohesive Model for the Analysis of Track Structure

Height Deviation Detection of Rail Bearing Platform on High-Speed Railway Track Slab Based on Digital Image Correlation

Height Deviation Detection of Rail Bearing Platform on High-Speed Railway Track Slab Based on Digital Image Correlation

Feasibility Study on the Solution of Replacing Track Slab with Lateral Pushing Rail in One Maintenance Window Time

Feasibility Study on the Solution of Replacing Track Slab with Lateral Pushing Rail in One Maintenance Window Time

Research on a Trackside Concrete Reinforcement Scheme of a Small Radius Curve at a Junction Section of a Modern Tram

Abstract In order to ensure the normal use of a junction section of a modern tram, this paper mainly studied a trackside concrete reinforcement scheme. Firstly, the entire non-reinforcement system model with a small radius curve composed of rail, fastener, fastener cover, flexible material, asphalt layer and track slab was established using the ABAQUS finite element software, and the stress distribution and deformation state of the asphalt layers of the non-reinforcement system model under the social vehicle load were analyzed. Then, the whole system model of the concrete reinforcement scheme was founded, and the stress and deformation of the asphalt layers under the same load were investigated. Finally, the calculation results of the concrete reinforcement model were com-pared with those of the non-reinforcement model, and the reinforcement effect was studied. The results show that the concrete reinforcement scheme significantly reduces the stress and deformation of the asphalt layers and improves the stress distribution and deformation state of the asphalt layers.

Comprehensive system limit state function model and its application for CRTS II track slab

ABSTRACT Considering safety and serviceability simultaneously, a comprehensive system limit state function (LSF) model and its application for CRTS II track slab is analyzed. First, a comprehensive system LSF model is proposed, and the procedure of comprehensive system reliability analysis is developed from integrating the method of moments with finite element (FE) code. Second, based on the proposed model, comprehensive system LSF of CRTS II track slab is constructed, considering five important safety failure modes and three important serviceability failure modes. Then, comprehensive system reliability of a CRTS II track slab on simply supported viaduct is analyzed using the proposed method, and the result is compared with general system reliabilities considering safety and serviceability separately. It is found that the proposed comprehensive system LSF model has a flexible form and the proposed methodology can be efficiently applied for comprehensive system reliability assessment. It is also found that comprehensive system reliability analysis is more appropriate compared with general system reliability analysis, and thus, comprehensive system reliability results can help to determine an appropriate maintenance strategy and ensure the safety operation for high-speed trains.

Monitoring Track Transition Zones in Railways.

This manuscript presents the first measurement program and data collection on the Dinatrans track transition solution after it was installed in a track section in the north of Spain (Galicia). The Dinatrans solution was created to address the limitations of several track transition solutions. This novel solution consists of two inner and outer rails from slab track to ballast track, pads with different stiffness over sleepers of variable lengths installed from ballast track to slab track, and a simple substructure formed by non-structural concrete poured over the natural ground. The main objective of this research was to assess the suitability and the initial performance of the Dinatrans track transition solution. The measured variables for these initial real-world tests were vertical accelerations on sleepers, shear stress on rails, vertical displacements on rails and vertical displacements on sleepers. All measurements of these variables were obtained in an in-situ program by installing vertical accelerometers and LVDTs on the track structure and extensometer gauges on the rails and sleepers. The methodology and the procedures followed are described. The Dinatrans initial solution was compared with the Standard solution used in Spain using these initial measurements. This field analysis provides an initial understanding of the performance of the new track transition. Further measurements will be required to check the track transition performance over the long term; however, no maintenance works have been necessary since construction (2016).

Analysis on mechanical characteristics of CRTSII slab ballastless track structures in rectification considering material brittleness

To analyze the influence of rectification on the CRTS Ⅱ slab ballastless track structure, ABAQUS, a Finite element software, was used to establish the mechanical analysis model of the CRTS II slab ballastless track. Consequently, the model reliability was verified by the field measurement results. The influence of different dissociation lengths, construction temperature and rectification distance on tack structure was analyzed in detail, and the mechanical properties of the structure after cracking were considered. From the systematic calculation and analysis of stress and deformation of CRTSII slab ballastless track structure during the deflection rectification process, the following research conclusions were deduced: (1) An the increase in one-time single-point deflection rectification range, resulted in a corresponding increase in the maximum rectification of track slab, CA mortar and support; (2) An the increase in the absolute value of deflection rectification temperature for one-time single-point, led to a linear increase in the maximum rectification of the track slab, CA mortar and support. The maximum rectification of support increased from 1.34 mm to 2.12 mm; (3) A maximum rectification of 1.44 mm was obtained at the CRTS II critical drop temperature of −4.4℃ specified by the code for design of concrete structures of railway bridge and culvert and the code for design of concrete structures; (4) An increase in pushing points distance from 2 m to 3 m resulted in a reduction in the maximum rectification of track slab, CA mortar and support by 1.25%, 1.28% and 1.32%, respectively. However, the tensile strain of the track slab and support was reduced by 8.72% and 12.14%. (5) Comparing the results of cracked and non-crack models, the maximum rectification of the track slab, CA mortar and support increased by 10.24%, 11.41% and 10.38%, respectively, while the maximum strain reduction of track slab, CA mortar and support reduced by 13.10%, 23.11% and 17.85%, respectively.

GRNN Prediction Model for Temperature-Induced Deformation of CRTS II Unballasted Slab Track

The General Regression Neural Network (GRNN) is one of the algorithms of artificial neural networks (ANN) that receives much attention in prediction applications. This research used the GRNN to predict the temperatureinduced deformation of unballasted track structures based on experimental data considering external weather conditions, such as sunshine duration, rain conditions, daily maximum temperature, daily minimum temperature, and daily average wind speed. The GRNN network predicts the average absolute error of the prediction results (0.0318 ℃), the maximum absolute error (1.7729 ℃), and the GRNN prediction sample mean squared error (0.070701). The average relative error is 0.32%. The finding of this study shows that the GRNN prediction method has good accuracy and robustness. Furthermore, it can promote the research of unballasted track temperature fields that are related to concrete structures.

Vibration-reduction optimization of the point-supporting floating-slab track based on local resonance mechanism

With the continuous increase of subway operating mileage, the problem of subway vibration has become more and more significant. Nowadays, the point-supported floating-slab track is recognized as the best method to control track vibration, which is mainly designed based on the mass-spring-damping theory. How to further improve the vibration control ability of the point-supported floating-slab track? In this paper, a new type of rubber point-supported floating slab track is designed based on the local resonance theory. Through calculation and dynamic test, it is obtained as follows: (1) The band gap of the point support structure by local resonance type depends on the two vertical vibration modes. (2) As the elastic modulus of the cladding layer increases, the bandwidth of the band gap of the corresponding structure increases significantly. (3) The increase of the vibrator density can increase the bandwidth, while reducing the start and stop frequencies, which is beneficial to attenuate the resonance of the floating-slab track. (4) The cushion material parameters of point support structure by local resonance type 2 will not affect the band gap. The increase in sleeve density will reduce the band gap, which is not conducive to vibration reduction. Local resonance type floating-slab track will be the development direction of track vibration-reduction measures in the future.

Study on fatigue damage laws and life prediction of CRTS-II ballastless track slab

To analyze the fatigue damage laws and fatigue life prediction, six full-size CRTS-II ballastless track slabs were tested under fatigue cyclic loading conditions. The main parameter considered was the fatigue load level that ranged from 0.5 to 0.675 Pu (the ultimate static capacity). The results indicate the following: (1) the slab under the load level of 0.5 Pu showed a slight reduction in capacity and deflection after 3,000,000 cycles, and its residual strength was only reduced by 3%. (2) the fatigue limit of the slab cannot exceed 0.6Pu (survived 2,000,000 cycles), because the stiffness and the residual deflection of the slab increased significantly at the increased the load level. (3) Based on the Palmgren-Miner cumulative damage criterion and the test results, the fitted formulas obtained from experimental results can predict the fatigue life of the slabs under both constant amplitude fatigue load and variable amplitude load.

Stress distribution in reinforced railway structures

This paper evaluates the performance of a geosynthetic reinforced soil retaining wall (GRS-RW) system as an alternative to a conventional railway embankment. The aim is to investigate the behaviour of the GRS-RW system in terms of displacements and stress levels at different locations in the track and substructure. Full-scale laboratory experimental testing is carried out on a GRS-RW structure, supporting sections of ballasted and slab track, under moving loads at 360 km/h. The tracks are supported by a low-level fully confined conventional embankment and a GRS-RW system, which are constructed to high-speed standards. Displacement transducers and earth pressure cells are placed at different locations to record the displacements of the track and the stress levels in the substructure. The test results show that the pressure levels on the GRS-RW wall are negligibly small for the particular test setup, proving the GRS structure under the action of compaction reached its active state. This means that the reinforced soil was self-supporting under its self-weight and train loads, meaning there was minimal pressure on the walls. Therefore, GRS-RW systems are better alternatives to traditional earth embankments due to enhanced soil stabilisation and less land take.

Comparison of the effects and efficiency of vertical and side tamping methods for ballasted railway tracks

The relatively high maintenance costs of the ballast track are related to the short lifecycle of the ballast layer. The current vertical ballast tamping technology (e.g., Plasser & Theurer, Matisa, etc.) causes high ballast destruction and is neither applicable for unconventional sleepers’ designs nor slab tracks. The side tamping method presents an alternative, ballast saving, and sleeper form independent ballast tamping technology. This paper compares the ballast layer compaction and its resistance to permanent settlements accumulation after the vertical and the side tamping methodologies. Scaled models of ballast layer and tamping units and scaled simulation with discrete element method (DEM) were applied for the comparison. In the laboratory tests, the ballast compaction along the sleeper was estimated using the measurements of elastic wave propagation. The settlements resistance for both tamping methods was estimated under the vibration loading. The tests’ results show 5–7% higher compactness of the ballast layer under the sleeper ends for the side tamping method. The settlement intensity of the ballast layer after the vertical tamping is higher than for the side tamping method. In discrete element modeling, the performed laboratory tests were simulated. The compactness of the ballast bed, as well as the residual stresses, were determined in MATLAB. The side tamping technology provided five times higher residual stresses in the ballast layer below the sleeper than in the case of vertical tamping, which can be explained by the more stable and dense layer resulting from the side tamping ensures higher interlocking between the grains. The simulation of the wave propagation shows an influence of the residual stresses on the wave propagation velocities. The simulated wave propagation velocity was more than two times higher for the side tamping than for the vertical one.

A further understanding on the strength development of cement pastes in the presence of triisopropanolamine used in CRTS III slab track

Accelerators are commonly used in the self-compacting concrete of CRTS III slab track to advance its strength development in cold areas. Triisopropanolamine (TIPA) is a known accelerator, and its influences on the strength development of hardened cement pastes (HCPs) were discussed based on a further understanding of cement hydration and microstructure. The results show that the addition of TIPA visibly heightens hydration degree at each age because it triggers the reaction of C4AF and gently promotes C3S hydration. At low dosages, more hydrates deposited in capillary pores facilitate a refined pore structure and therefore, significantly increase the early and late strengths. On the contrary, a high dosage of TIPA results in a loose and porous structure at an early age owing to the emergence of numerous AFm platelets and the reduction of Ca(OH)2 crystals, so that the heightened hydration degree only slightly increases the early compressive and flexural strengths. At a later age, high dosages of TIPA cause an increase in the volume of harmful pores (greater than 50 nm), which may result from the appearance of some pores full of fractional AFm and the changed morphology of Ca(OH)2. Therefore, the late compressive strength of HCPs remains almost unchanged under the positive effect of the heightened hydration degree coupled with the negative effect of the increased volume of the harmful pores. In contrast, the late flexural strength sharply decreases, which is ascribed to both of the increased volume of the pores larger than 50 nm and the morphological changes of hydration products.

Across-arc variations in K-isotope ratios in lavas of the Izu arc: Evidence for progressive depletion of the slab in K and similarly mobile elements

In subduction zones, fluids rise from the slab to the mantle, causing metasomatism and flux melting of the mantle to produce arc magmas. The transfer of material from slab to mantle and, in turn, to arc crust is an important control on the long-term chemical evolution of the mantle and continental crust. In this study, we investigate the transport of K in subduction zones by exploring the systematics of K stable-isotope variations in lavas of the Izu arc. We find that the Izu lavas have isotopically heavy K relative to estimates for midocean ridge basalt (MORB)-source upper mantle. Moreover, the δ41K values of the lavas are clearly heavier than those of subducting sediments and are probably heavier than subducting altered ocean crust. An across-arc decrease in δ41K values is apparent. Arc-front lavas are heavier than the mantle by about 0.22‰ (median), whereas rear-arc lavas are heavier by only about 0.08‰ (median). The heavy K-isotope compositions of the arc lavas may arise from isotopic fractionation during slab dehydration, where light K is preferentially retained in phases such as phengite in the slab. The across-arc decrease in δ41K values may be due to progressive breakdown of these phases, and to associated depletion of the slab in heavy K. Variations in the relative contributions of different source materials—igneous ocean crust, sediment, and mantle peridotite—may also play a role. In particular, we explore a possibility, motivated by radiogenic-isotope studies, that the slab signal in K isotopes may be attenuated in the rear arc as a result of extensive fluid-mantle interaction. If K isotopes do track slab dehydration, then K isotopes provide insight into the transfer of K and similarly mobile elements out of the slab and into the upper mantle and arc crust. Lastly, we observe extreme isotopic variations in some of the lavas, which we interpret to result from crustal-level or Earth-surface processes that affect only a subset of the lavas.