Railway Track Structure Research Articles

Modeling of railway track integrating a shock-absorbing mat at the sleepers-ballast interface using eigenfunctions of displacement

Damage caused to railway tracks and the surrounding environment during trains passage have become a real concern for those involved in the railway sector over the years. To find a solution for this problem, several approaches have already been implemented on railway tracks in some countries. Despite the efforts made in this area, the problem of ground vibration induced by railway traffic still remains a concern. Therefore, many studies have been focused on solutions to attenuate, even cancel vibrations effects on the track and nearby environment. This work has presented a modeling of a ballasted railway track with a shock-absorbing mat or Under Sleepers Rubber Mat (USRm) at the sleepers/ ballast interface. Using the equation of wave propagation in the ground and the constitutive law, the eigenfunctions of the displacement vector were determined. By coupling the equations of the track and those of the ground, the displacement, the velocity, and the acceleration of each track component, as well as the stress on the ground surface were expressed. The Newmark numerical method was used to represent these variables and to highlight the (USRm) influence on the dynamic behavior of the different track component. Comparison of the results obtained with the proposed railway model shows a reduction in vibration amplitudes of 64.9% and 94%for the rail, 86.5% and 56.25% for the sleepers. At the ground surface, the attenuation of vibration is evaluated at 53% and 6.85%, respectively for linear and nonlinear cases. The insertion of the shock-absorbing mat (USRm) in the railway track structure also reduces stress at the ground surface. The configuration of the railway track with a damping mat (USRm) therefore significantly reduces the transmitted vibration to the ground and to the nearby structures. It also contributes to the stability of the track and the improvement of its performance. The proposed railway track model with a shock-absorbing mat can be considered as a solution to reduce vibrations generated on track and the ground during trains passages.

CONSTRUCTION OF THE RAILWAY TRACK OF UKRAINE AND PROSPECTS FOR THEIR IMPROVEMENT

The goal. The process of improving the design of the railway track requires a detailed study of the history of the development of its structural elements, methods of combination, interconnections and limits of mutual influence. Modern track designs are the result of many years of hard work by scientists and long operational tests. Some designs were inventions at the time, some were breakthrough technologies, some remained just ideas, and some have existed for more than a century. The study of the history of the development of railway track structures and modern existing structures in operation made it possible to identify a promising direction for improvement and further development, taking into account the existing problems on the mainline transport tracks and industrial enterprise tracks. Reinforced concrete sleepers and intermediate fasteners that allow for track gauge adjustment are the railroad track structure that should be improved in the coming years. Improving railroad track design is a continuous process in the development of rail transport. Recently, new track designs have been introduced on Ukrainian railways. As a rule, the problems of track facilities are first considered and technical tasks are formulated. Then, a public discussion is held in the scientific and practical environment and an appropriate development strategy is born. Such a strategy is reviewed and approved at scientific and technical meetings and specialized commissions. This article aims to identify promising areas for improving the track design and solving the problems of installing and operating a continuous track by analyzing existing designs and world experience of railways. Methods. Methods of scientific analysis and synthesis of track development design, methods of analytical geometry. Results. Based on the analysis of the history of the development of the railroad track structure and modern designs, a promising direction of improvement is proposed. A promising railroad track structure is defined as a reinforced concrete sleeper and fasteners capable of forming an adjustable track gauge of up to 1545 mm. At the same time, it is necessary that the new design has sufficient stability of the jointless track plates. Practical significance. The application of the proposed structure within small radius curves, provided that the results of trial operation and testing of the established procedure are positive, will reduce the operating costs associated with the current maintenance of the tracks, expand the scope of laying of the jointless track and use reinforced concrete sleepers in small radius curves at industrial enterprises.

Compactability of granular materials increasing the durability of operated railway track structure and subgrade

The progressive degradation of the railway track structure increases the impact of the rolling stock transferred to the track and subgrade, which requires ensuring appropriate track support through the selection of material, grain size and density of granular layers. The study presents research and analysis of increased loads transferred to the ballast. By using protective layers of the track substructure made of appropriate materials, proper conditions of cooperation between the track and subgrade are achieved, ensuring the elastic operation of the surface and minimizing its permanent deformation. Currently used methods and solutions for strengthening and stabilizing granular materials are described. Particular analysis was carried out to ensure proper support of the track grid by providing appropriate granular material and its compaction (including ballast obtained from recycled – unsorted stone).

Adaptive Vibration Monitoring of Railway Track Structures Using the UWFBG by the Identification of Train-Load Patterns

Due to the capability of multiplexing thousands of sensors on a single optical cable, ultra-weak fiber Bragg grating (UWFBG) vibration sensing technology has been utilized in monitoring the vibration response of large-scale infrastructures, particularly urban railway tracks, and the volume of the collected monitoring data can be huge with the great number of sensors. Even though the train-induced vibration responses of urban railway tracks constitute the most informative and crucial component, they comprised less than 7% of the total operational period. This is mainly attributed to the temporal sparsity of commuting trains. Consequently, the majority of the stored data consisted of low-informative environmental noise and interference excitation data, leading to an inefficient structural health monitoring (SHM) system. To address this issue, this paper introduced an adaptive monitoring strategy for railway track structures, which is capable of identifying train-load patterns by leveraging deep learning techniques. Inspired by image semantic segmentation, a U-net model with one-dimensional convolution layers (U-net-1D) was developed for the pointwise classification of vibration monitoring data. The proposed model was trained and validated using a dataset obtained from an actual urban railway track in China. Results indicated that the proposed method outperforms the traditional dual-threshold method, achieving an Intersection over Union (IoU) of 94.27% on the segmentation task of the test dataset.

Оценка интенсивности накопления остаточных деформаций основной площадки земляного полотна на участках обращения тяжеловесных и длинносоставных поездов

Objective: the article presents an assessment of the intensity of accumulation of residual deformations of the main platform of the roadbed in the areas of circulation of heavy and long-composite trains formed from wagons with an axial load of up to 25 tons. Methods: measurements of residual deformations of the main site of the roadbed were carried out by geodetic methods by laying a closed leveling course. To do this, each experimental site was equipped with soil stamps installed on the main site of the roadbed and reference points. The measurements were carried out from 30.05.2022 to 08.11.2023. Results: as a result, the dependences of the accumulation of residual deformations of the roadbed on the missed tonnage have been established for various railway track structures, operating conditions and engineering and geological conditions. Practical importance: measures are proposed to reduce the intensity of accumulation of residual deformations of the main site of the roadbed.

Experimental Monitoring of Dynamic Parameters of the Sub-Ballast Layers as a Prerequisite for a High-Quality and Sustainable Railway Line

Monitoring dynamic load transfer from train traffic to sub-ballast layers is crucial for verifying the reliability and safety of railway lines, assessing the design cost-effectiveness and achieving minimum environmental impact. For this purpose, measurements in labs, in situ or modeling the influence of dynamic loads on the immediate and long-term roadway quality are often performed using suitable software. The available test sections enabled monitoring of the dynamic loads and optimizing the critical spots where increased dynamic effects from railway traffic may occur. The subject of this paper is the calibration of the sensors installed in the different test sections of the trans-European corridor number V. As a result, the necessary input parameters for the subsequent numerical modeling of the dynamic effects on the track substructure and vibration propagation on the available sections of the upgraded railway line were obtained. The sensor calibration was carried out on the experimental field, part of the Experimental Basis of the Department of Railway Engineering and Track Management. As part of the calibration, the sensitivity of the sensors embedded in the track bed to the applied dynamic loads resulting from the impact effects of the lightweight deflectometer was assessed. The result of the calibration was the demonstration of sufficient sensitivity of the sensors and their suitability for implementation in an actual railway track structure, with the aim of obtaining relevant values of the response of the sub-ballast layers to dynamic loads and assessing the operational impacts on the sustainable environment. Also, the main result of the research was the possibility of using the theoretical–experimental route to optimize the layers of the railway body.

The influence of anisotropic properties of the under-rail base on the track dynamic settlement

The article presents the results of a study of the anisotropy of the under-rail base on the dynamic settlement of sections of transitional stiffness reinforced with bottomless boxes. It is proposed to model the railway track by flat elements, each of which is represented by an anisotropic plate resting on a deformable base with its own deformability parameters. Three main directions of change in the mechanical and geometric characteristics of the structure are identified: horizontal directions along the rail strands, transverse directions along the sleepers, and vertical directions down from the level of the rail head. Setting boundary conditions for individual fragments of the track structure and varying the anisotropy coefficients allows to achieve a good correspondence between the real railway track structure and its mathematical model. Graphical dependencies for the vertical displacement of points on the median surface of a flat element modeling a segment of a railway track were constructed and analyzed based on the results of determining the frequencies of natural oscillations.

Analysis of Indonesia’s Railway Track Structure Behavior Under Double-Stack Freight Train Loading

The growing number of freight transported using railway transport is massive. Indonesia targeted 995,500,000 tons of freight transported using the railway mode. Double-stack train is one solution to increase thefreight tonnage of the train without adding the number of operations of the train. The 3D ANSYS model ismade to see the structural behavior of railway tracks under the double-stack train load using 1067 mm and 1435 mm gauge from Indonesia’s railway track regulation. It was also modeled with several speeds to observe its influence on the structure. It is known that in all output parameters of deformation, stress, and strain, the 1435 mm gauge actsbetter for the structure than the 1067 mm gauge. The subgrade service life also became longer in the 1435 mm gauge structure. Lower speed also gives a better impactonthe structure of the track and possible to give longer service life for subgrade.Further research isneeded to observe the railway track structural behavior in cyclic loading and the possibilityofreinforcing the subgrade. The lab-scale test also needed to validate the analysis.

Leveraging railway topology to automatically generate track geometric information models from airborne LiDAR data

Geometric information modelling from point cloud data (PCD) is a fundamental step of the digital twinning process for rail infrastructure. Currently, this onerous procedure outweighs the anticipated benefits of the resulting model and expends 74% of the modellers' effort on converting PCD to a model. The cost of the resulting geometric information models (GIM) can be reduced by automating the modelling process. State-of-the-art methods cannot offer large-scale GIM generation required over kilometres without forfeiting precision and manual cost. This paper addresses the challenge of achieving such automation by leveraging the highly standardised topology of railways to automatically generate GIMs of rail track structures.The method first automatically segments rails and track beds, delivering labelled point clusters of track structure elements. Next, it converges the segmented rails with pre-defined parametric assemblies of different rail profiles and uses a mesh-based approach to reconstruct the geometry of the track bed, delivering industry foundation classes (IFC) files of railway track structure elements. Experiments on 18.5 km railway PCDs yielded an average segmentation of 98.1% and 94.9% F1 scores and overall modelling accuracy of 3.5 cm and 2.8 cm root mean square error (RMSE)s for rails and track beds. The proposed method can realise an estimated time savings of 88.9% without needing any manual inputs.

Study on the seismic influence coefficient of track irregularity on the train dynamic effect of high-speed railway bridge

Track irregularity is an important factor affecting the train-track-bridge system interaction, and for the seismic design of the track-bridge system, the study of the law of the influence of track irregularity on the train dynamic effect is of great theoretical significance. Based on this, the finite element models of China railway track structure (CRTS) II plate high-speed railway simple-supported girder bridge and CRH2C high-speed train model are developed and compared with the shaking table test results to verify their validity. Considering track irregularity and earthquake randomness, a sample library of the train dynamic effect of the track-bridge system under earthquake is established, the probabilistic statistical characteristics of the train dynamic effect are analyzed, and the influence level of track irregularity on the train dynamic effect of the track-bridge system under earthquake is studied, and the standard value of track irregularity influence coefficient of train dynamic effect based on probability guarantee rate is proposed. The results indicate that: the influence of track irregularity on the seismic response of bridge structure is slight, with their greatest impact not exceeding 1%. However, it has a significant impact on the seismic response of track structures. The standard values of the sliding and mortar layers’ track irregularity influence coefficients are 1.49 and 1.71, respectively, at 0.1 g. Under various peak ground acceleration (PGA) settings, the fasteners’ standard values for the track irregularity influence coefficient are less than 1.1. Additionally, the degree of influence of track irregularity on the seismic response of track structure decreases significantly as the PGA increases.

Long-term temperature acceleration effect of solar radiation heating on chloride transport in the CRTS III multilayer structure

The service life of high-speed railway track structures located in coastal areas may be shortened by chloride erosion due to the marine environment. This study aims to simulate chloride transport within the track structure by boundary condition models based on high-precision climate data and structural damage. The established numerical models consider various factors, including structural damage, historical exposure data of air temperature and relative humidity, temporal resolutions, solar radiation history, and the deposition rate of atmospheric chloride. The main conclusions are as follows: The maximum vertical temperature gradient of the track slab is roughly 81K/m, and the daily average temperature differences between air and surface concrete in July and February are around 9.6°C and 4.8°C, respectively. The chloride flux boundary derived from the chloride deposit rate is nearly 1 × 10-9mol/(m2s) to 10 × 10-9mol/(m2s) under a marine atmospheric environment. Step functions of daily average and monthly average temperature can improve almost the same prediction accuracy of chloride diffusion, and increasing the monthly average temperature curve by 10°C can roughly estimate the upper limit of temperature acceleration.

ASSESMENT OF THE POSSIBILITY OF FOAM GLASS APPLICATION IN THE SUB-BALLAST LAYERS

The paper investigates whether foam glass could reduce the structural thickness of the protection layer in the construction of the railway track (saving of natural materials – crushed aggregate) and, at the same time, also provide sufficient thermal protection of the frost-susceptible subgrade surface. It also discusses whether the incorporation of foam glass would have a relevant effect on the increase of the deformation resistance of the railway track structure at the level of the sub-ballast upper surface. Following these assumptions, the paper presents the results of experimental measurements of the deformation resistance of the modified structural composition of the sub-ballast layers (with an embedded foam glass layer) and their comparison with the results determined on a structure with a standard composition of the sub-ballast layers (crushed aggregate sub-ballast layer/protective layer). Also, numerical and mathematical analysis of the influence of the built-in thermal insulation foam glass layer on the reduction of the structural thickness of the protective crushed aggregate layer in terms of the effect of climatic factors is conducted in the paper. The mathematical model, developed by the research, provides the possibility of continuous monitoring of the change in the railway track structure freezing depending on climatic characteristics.

Influence of damping on seismic-induced track geometric irregularity spectrum in high-speed railway track-bridge system

Track irregularities are an important factor affecting the safety, smoothness, comfort, and lifespan of high-speed railway track structures. Damping greatly affects the seismic response, and the influence of damping on seismic-induced track geometric irregularities is of significant interest. In this study, the simple-supported beam bridge of the CRTS-II ballastless track high-speed railway was adopted as the research object. A power spectral density curve spectrum of seismic-induced track geometric irregularity based on guarantee rate was established, and the influence of structural damping ratio on the power spectral density curve under different earthquake intensities was analysed. A simplified calculation method for power spectral density curve of seismic-induced track geometric irregularity was proposed. The main findings of this work are as follows: (1) Seismic-induced track irregularities of high-speed railway bridges are dominated by alignment irregularity, and a segmented polynomial function can be fitted to the power spectral density curve of the seismic-induced track irregularity based on guarantee rate; (2) Seismic-induced track irregularities of high-speed railway bridges worsen as structural damping decreases and peak ground acceleration increases; (3) More spikes are observed in the high-frequency waveband of the power spectral density curve, and seismic-induced track irregularity results in more high frequency periodic components.

The effect of asphaltic support layers on slab track dynamics

The deployment of asphaltic support layers (ASLs) within railway track structures has the potential to increase track bending stiffness, assist moisture runoff and provide a platform for track construction. These merits have increased its usage within the rail industry, however the understanding of asphaltic track dynamics during train loading remains limited. Therefore, the primary aim of this study is the development of new knowledge into the dynamic behavior of concrete slab track systems enhanced with asphaltic underlays. To do so, a numerical simulation approach is used, comprised of two sub-models: 1) a coupled multi-body vehicle−track model, for the purpose of computing wheel/rail forces; and 2) a 3D dynamic finite element track-ground model to simulate stress wave propagation in the sub-structure. The models are validated using both analytical results and field tests, and then used to simulate slab track systems with ASL thicknesses of: 0, 0.05, 0.07, 0.10, and 0.15 m. First the dynamic response at locations both near and far from the track joints are compared to quantify the asphaltic foundation stresses, deflections, accelerations and strains. It is found that stress concentrations occur near the concrete base joints and are an important consideration for ASL design. Next, asphalt concrete durability at 400 km/h line speed is explored considering seasonal temperature variations and it is found that the expected cumulative damage meets serviceability requirements. Finally, the influence of different asphaltic layer thicknesses on reaction modulus is discussed, concluding that the optimal thickness range, considering plastic deformation and construction constraints, is between 0.07 m and 0.10 m.

Investigation on Effect of Reflective Coating on Temperature Field of CRTS Ⅱ Slab Ballastless Track under Sunlight

The internal temperature variation of ballastless track is very complicated under the effect of a sunlit environment, and there are serious transverse and vertical temperature gradients, which will cause cracking and deformation of the structure. In this paper, an ANSYS temperature effect analysis model for ballastless track, considering box girder structure, is established based on the environmental information of the bridge and the characteristics of the structural system. The model considers the influence of solar radiation intensity, wind speed, air temperature, geographical location, bridge orientation, material parameters, and other factors on the boundary conditions, and can meet the needs of the daylight temperature response analysis and calculation of any complex bridge structure. On this basis, the effect and applicability of a solar reflective coating on ballastless track cooling are studied. The results showed that the calculated results of the finite element model agree well with the measured results. Under the high-temperature conditions in summer, sunlight and ambient temperature mainly have significant effects on the temperature and temperature gradient of the track slab, and the maximum vertical temperature gradient reaches 74.48 °C/m. The reflective coating can significantly reduce the track slab’s temperature and vertical temperature gradient, with a maximum temperature gradient reduction of 34%. The transverse temperature gradient of the track slab can be reduced by up to 54% by further application of the side reflective coating. This study can promote the application of reflective coatings on high-speed railway track structures.

Incompatible thermal deformation of interlayers and corresponding damage mechanism of high-speed railway track structure

In the service period, the instability of ballastless track bed are mostly related to the damage of interlayers which are mainly resulted from the incompatible thermal deformation of interlayers. The temperature field within the ballastless track bed shows significant non-uniformity due to the large difference in the materials of various structure layers, leading to a considerable difference in the force bearing of different structure layers. Unit Ballastless Track Bed (UBTB) is most significantly affected by temperature gradient. The thermal deformation of interlayers within UBTB follows the trend of ellipsoid-shape buckling under the effect of the temperature gradient, resulting in a variation of the contact relationship between structure layers and a significant periodic irregularity on the rail. When the train travels on the periodically irregular rail, the structure layers are locally contacted, and the contact zone moves with the variation of the wheel position. This wheel-followed local contact greatly magnifies the interlayer stress, causes interlayer damage, and leads to a considerable increase in the bending moment of the track slab. Continuous Ballastless Track Bed (CBTB) is most significantly affected by the overall temperature variation, which may cause damage to the joint in CBTB. Under the combined action of the overall temperature rise and the temperature gradient, the interlayer damage continuously expands, resulting in bonding failure between structural layers. The thermal force in the continuous track slabs will cause the up-heave buckling and the sudden large deformation of the track slab, and the loss of constraint boundary of the horizontal stability. For the design of a ballastless track structure, the change of bearing status and structural damage related to the incompatible thermal deformation of interlayers should be considered.

White Layer in M76 High Carbon Rail Steel: Formation Mechanism and Properties

High-frequency vibrations resulting from many factors under loads existing in the wheel-rail system have a huge impact on the structure and properties of rail steel: there are signifi contact stresses in the surface layer that affect strength characteristics and overall fatigue of the railway track structure. Such an impact results, in particular, in the formation of the so-called White Layer (WL): a hardened layer on the surface of the base material, resistant to chemical etching, and having high hardness (above 1000 HV) and brittleness.The objective of the research was to study the features of the formation mechanism, as well as the properties of the white layer formed on the metal surface using an integrated approach, namely, of destructive testing methods, electron microscopy, XRD, metallography, and microhardness measurements.The reliability of experimental studies is due to the use of standardised test methods, developed methods of destructive and non-destructive testing in the main areas, the involvement of an accredited and certified laboratory, which makes it possible to fulfill in full the tasks set with appropriate quality.The results of the research allowed to present an analysis of the white layer, the formation of which took place in high-carbon M76 rail steel after cyclic tests with a 20 kHz frequency. The morphology, phase composition, and microhardness of these inclusions have been studied in detail in comparison with the base metal. It is shown that the white layer is highly dispersed, pearlitelike, featureless inclusions of a ferrite-cementite structure, while their microhardness is 3–4 times higher than the original steel and is of 1000–1200 HV. A possible explication of a mechanism of the formation of a white layer is suggested: crushing of ferrite and cementite, which are part of pearlite, without intermediate phase transformations.

Application of a modern laser technique to evaluate the performance of recycled railway ballast

The performance of railway track structure is influenced by the ballast shape properties including roundness, flatness, elongation, sphericity, angularity and surface texture. The challenge is how to accurately measure the irregular shapes of ballast materials and directly link them to performance. In this paper, a modern three-dimensional laser technique was used to determine shapes of freshly produced crushed ballast and recycled ballast sampled from the heavy-haul coal line in South Africa. The objective was to investigate the effect of ballast shapes on settlement (i.e. permanent deformation). All five ballast materials were scanned in the three-dimensional laser scanning system and the data collected was processed to reconstruct three-dimensional models of the ballast particles. The results obtained were used to develop a chart to classify ballast shapes and link these shapes physically with settlement determined from a triaxial testing programme. Based on the triaxial test results, new empirical models were developed to determine settlement on the route corridor of the heavy-haul coal line. It is anticipated that outcomes of this study would assist with quality assessments and railway ballast maintenance in the field.

Dynamic response of vehicle-track interaction at the bolted rail joint in the presence of the polygonal wheel

Rail joints are the weakest link in the railway track structure due to the presence of discontinuities in the track stiffness and wheel-rail contact geometry. This paper presents the dynamic response of vehicle-track interaction at the bolted rail joint (BRJ) in the presence of polygonal wheel wear. A three-dimensional coupled vehicle-track dynamic model was established using the finite element method (FEM) and the multi-body system (MBS) approach, in which the flexibilities of the wheelset and track are taken into account. The proposed dynamic model is validated by the comparisons of field measurement and calculated vertical axle-box acceleration in time and frequency domains. The effects of the flexible wheelset in the presence of polygonal wear on the vehicle-track dynamic interaction at the BRJs are illustrated through comparisons with those obtained using without polygonal wheel model. The results show that the polygonal wheel wear and the rail joint irregularities can induce high-magnitude vertical wheel-rail contact force, and exacerbate the vibration responses of the axle box, the wheelset, and the rails. The simulation results also indicate that the wheelset bending modes, the P2 resonance due to rail joint excitation, and the track vibration modes have significant effects on the vertical vehicle-track dynamic interaction at the supported and suspended BRJs.

Decomposition methods for impact‐based fault detection algorithms in railway inspection applications

Railway track defects must be detected and repaired to ensure the safe operation of the railway. Signals generated by wheelset contact with rail discontinuities contain information about railway track structure and health. Each signal has a characteristic pattern, which is modified in the presence of defects. Signal decomposition is commonly used to extract characteristics from impact response signals. It is necessary to select an appropriate decomposition method for the wheel/rail impact signal. This paper presents a study of the effectiveness of decomposition methods to identify the most appropriate technique for classification of rail conditions. Vibration signals have been generated in experiments and decomposed. The signal characteristics are presented and energy-based methods are used in an evaluation of the different approaches. Standard deviation is used to assess the similarity of parameter value from different intrinsic mode functions (IMFs); maximum and minimum differences from the mean value are used to consider the effectiveness of each technique in identifying specific damage types. The evaluation shows that variational mode decomposition (VMD) is suitable for the rail application. Classifiers are applied to the outputs of the selected decomposition method. The results demonstrate the suitability of the approach for processing wheel/rail impact response signals to detect faults and improve safety.