High-speed Railway Track Research Articles

Study on structural health monitoring of vertical vibration of ballasted track in high-speed railway

The ballasted track structure of a high-speed railway repeatedly bears the action of vehicle loads, and the vibration energy is gradually diluted and dissipated due to the ballasted bed. It is difficult to monitor the structural health of ballasted track. By embedding sensors into the ballast, a ballast sensor was obtained. It was positioned on the ballasted track to study the structural health monitoring (SHM) under an impact excitation and to verify the Discrete Element Method (DEM)–Multi-body Dynamics (MBD) co-simulation model. Therefore, the SHM of the ballasted track is realized. The results showed that distributed ballast sensors can realize the SHM status of the ballasted track. Under an impact excitation, the peak of the main vibration frequency of the ballast at the sleeper box, sleeper end and ballast shoulder occurred at a frequency of 153 Hz. At twice the frequency, a secondary peak appeared in the ballast vibration amplitude at the sleeper box, while the vibration amplitudes at the sleeper end and ballast shoulder were suppressed. In low-frequency regime, the vibration damping performance of the ballasted bed structure was better than that in high-frequency regime. When the ballasted track structure was excited by high-frequency vibrations, the surface layer of the ballast at the sleeper box tended to splash, which affected the structural health state. Under the moving wheel load, both sides of the ballasted bed form a “cyclone” shape.

Systems and subsystems of track, control and management of high-speed railway

The article discusses the following issues: according to the current level of development and equipment of the existing network of railways in Ukraine, it is necessary to state the determination of the gauge of the high-speed line; the main characteristics of the highspeed rail system and the general requirements for laying the line; track systems and subsystems, as well as including their movement and control on free terrain, ensuring the safety of operation and transportation of passengers with the declared conditions of comfort and speed; the distance between the centres of the tracks increases in proportion to the speed of movement of passenger flows, which requires additional arrangement of the roadbed, taking into account the radii of the curves, the elevation of the outer rail, the angle of descent and ascent of the track, the equivalent taper, the slope of the rail, the profile of the rail head, such as rail and sleepers; lateral and vertical forces acting on the track. In order to ensure traffic safety at the maximum permissible speeds, it is necessary that the indicated vertical and lateral forces (static and dynamic) meet the requirements, which in turn depend on the above factors.

Analytical study on high-speed railway track deformation under long-term bridge deformations and interlayer degradation

Bridges are subjected to long-term deformations in addition to deformations under design loads. In high-speed railway bridges, long-term bridge deformation and potential degradation of materials may adversely impact the operation safety and riding comfort of the railway. While a high-speed railway network is being established in China, it is significant to understand the effects of long-term bridge deformation on track deformation for effective asset management. This study aims to develop an analytical model to investigate the roles of long-term bridge deformations and bridge-track interlayer degradation. Mechanical analysis is conducted to develop a track-bridge deformation model and derive closed-form solutions that can be applied in design and evaluation of high-speed railway bridges. The analytical study is validated against a three-dimensional finite element model, and used to investigate the effects of key parameters (e.g. bridge deformation amplitude, span length, fastener stiffness, and mortar layer stiffness). This study provides a method to quantitatively evaluate track deformation due to bridge deformations and interlayer degradation. With the developed formulae, real-time condition assessment of high-speed railway track can be performed based on real-time monitoring of bridge deformations.

Mechanical characteristic variation of ballastless track in high-speed railway: effect of train\u2013track interaction and environment loads

Due to the fact that ballastless tracks in high-speed railways are not only subjected to repeated train–track dynamic interaction loads, but also suffer from complex environmental loads, the fundamental understanding of mechanical performance of ballastless tracks under sophisticated service conditions is an increasingly demanding and challenging issue in high-speed railway networks. This work aims to reveal the effect of train–track interaction and environment loads on the mechanical characteristic variation of ballastless tracks in high-speed railways, particularly focusing on the typical interface damage evolution between track layers. To this end, a finite element model of a double-block ballastless track involving the cohesive zone model for the track interface is first established to analyze the mechanical properties of the track interface under the loading–unloading processes of the negative temperature gradient load (TGL) followed by the same cycle of the positive TGL. Subsequently, the effect of wheel–rail longitudinal interactions on the nonlinear dynamic characteristics of the track interface is investigated by using a vehicle-slab track vertical-longitudinal coupled dynamics model. Finally, the influence of dynamic water pressure induced by vehicle dynamic load on the mechanical characteristics and damage evolution of the track interface is elucidated using a fluid–solid coupling method. Results show that the loading history of the positive and negative TGLs has a great impact on the nonlinear development and distribution of the track interface stress and damage; the interface damage could be induced by the wheel–rail longitudinal vibrations at a high vehicle running speed owing to the dynamic amplification effect caused by short wave irregularities; the vehicle dynamic load could produce considerable water pressure that presents nonlinear spatial–temporal characteristics at the track interface, which would lead to the interface failure under a certain condition due to the coupled dynamic effect of vehicle load and water pressure.

Analysis on the track quality evolution law of polyurethane-reinforced ballasted track in high-speed railway

Polyurethane-reinforced ballasted track (PRBT) can improve the integrity of ballasted track structures and satisfy the high-stability requirements of high-speed railways. In this study, the quality evolution law of PRBT structures after being launched into train service was analyzed, and a reference for structural optimization and maintenance operation was provided. The track geometric state of the PRBT test section of a high-speed railway was measured and monitored for nearly one year after it was launched into operation, and the ballastless track of the adjacent section was selected as a reference. The geometric states of the tracks were evaluated and compared using various parameters, including sliding standard deviation, average standard deviation, and track irregularity spectrum density. Results show that the track quality indexes of the test section, which were in operation for nearly one year, were slightly over the limit. Moreover, the fastener can be finely adjusted for the high-value index sections to further improve the ride comfort. The application effect of PRBT in the subgrade fracture zone was good, which could satisfy the requirements of high-quality transportation as well as the normal operation and maintenance of high-speed railway.

Seismic Responses of a High-speed Railway (HSR) Bridge and Track Simulation under Longitudinal Earthquakes

ABSTRACT The seismic vulnerability of high-speed railway (HSR) bridges may be overestimated or underestimated when the track structure is oversimplified in a finite element model. Thus, the author established a track-bridge model considering CRTS II slab ballastless track and a trackless-bridge model. The effect of track constraint on the seismic vulnerability of various bridge components and overall system was evaluated by comparing the seismic vulnerability curves of different models under longitudinal earthquakes. The track structure itself was also evaluated, and the multiple components of the track structure were found to be under threat of seismic damage and needed seismic risk assessment.

Arching Detection Method of Slab Track in High-Speed Railway Based on Track Geometry Data

During the long-term service of slab track, various external factors (such as complicated temperature) can result in a series of slab damages. Among them, slab arching changes the structural mechanical properties, deteriorates the track geometry conditions, and even threatens the operation of trains. Therefore, it is necessary to detect slab arching accurately to achieve effective maintenance. However, the current damage detection methods cannot satisfy high accuracy and low cost simultaneously, making it difficult to achieve large-scale and efficient arching detection. To this end, this paper proposed a vision-based arching detection method using track geometry data. The main works include: (1) data nonlinear deviation correction and arching characteristics analysis; (2) data conversion and augmentation; (3) design and experiments of convolutional neural network- based detection model. The results show that the proposed method can detect arching damages effectively, and the F1-score reaches 98.4%. By balancing the sample size of each pattern, the performance can be further improved. Moreover, the method outperforms the plain deep learning network. In practice, the proposed method can be employed to detect slab arching and help to make maintenance plans. The method can also be applied to the data-based detection of other structural damages and has broad prospects.

Full-scale multi-functional test platform for investigating mechanical performance of track\u2013subgrade systems of high-speed railways

Motivated by the huge practical engineering demand for the fundamental understanding of mechanical characteristics of high-speed railway infrastructure, a full-scale multi-functional test platform for high-speed railway track–subgrade system is developed in this paper, and its main functions for investigating the mechanical performance of track–subgrade systems are elaborated with three typical experimental examples. Comprising the full-scale subgrade structure and all the five types of track structures adopted in Chinese high-speed railways, namely the CRTS I, the CRTS II and the CRTS III ballastless tracks, the double-block ballastless track and the ballasted track, the test platform is established strictly according to the construction standard of Chinese high-speed railways. Three kinds of effective loading methods are employed, including the real bogie loading, multi-point loading and the impact loading. Various types of sensors are adopted in different components of the five types of track–subgrade systems to measure the displacement, acceleration, pressure, structural strain and deformation, etc. Utilizing this test platform, both dynamic characteristics and long-term performance evolution of high-speed railway track–subgrade systems can be investigated, being able to satisfy the actual demand for large-scale operation of Chinese high-speed railways. As examples, three typical experimental studies are presented to elucidate the comprehensive functionalities of the full-scale multi-functional test platform for exploring the dynamic performance and its long-term evolution of ballastless track systems and for studying the long-term accumulative settlement of the ballasted track–subgrade system in high-speed railways. Some interesting phenomena and meaningful results are captured by the developed test platform, which provide a useful guidance for the scientific operation and maintenance of high-speed railway infrastructure.

An Incentive Factor-Based Dynamic Comprehensive Evaluation on a High-Speed Railway Track

Peak management and mean management are common ways to manage the quality of high-speed railway tracks at present. The most popular method for evaluating such tracks is the track quality index (TQI) method, which can reflect the overall state of the equipment to a certain extent. However, this method is likely to ignore some potential risks that threaten the operation of a high-speed train. For more effective risk identification, an incentive factor-based dynamic comprehensive evaluation (DCE) method was introduced to assess the geometric parameters of a high-speed railway track. Moreover, the weights of geometric parameters were computed by a combination of the analytic hierarchy process (AHP) and entropy based on the correlation coefficient. The proposed method can highlight the sensitivity index of the geometric parameters, which is an advantage over the TQI method. A case study of a high-speed railway track was performed using the two methods, and the results were verified with the original data. It was found that the TQI method identified only one obvious risk while the proposed method identified one obvious risk and two potential risks. This suggests that the proposed method is more accurate in identifying the risky sections than the TQI method.

Structural health monitoring of high-speed railway tracks using diffuse ultrasonic wave-based condition contrast: theory and validation

Despite proven effectiveness and accuracy in laboratories, the existing damage assessment based on guided ultrasonic waves (GUWs) or acoustic emission (AE) confronts challenges when extended to real-world structural health monitoring (SHM) for railway tracks. Central to the concerns are the extremely complex signal appearance due to highly dispersive and multimodal wave features, restriction on transducer installations, and severe contaminations of ambient noise. It remains a critical yet unsolved problem along with recent attempts to implement SHM in bourgeoning high-speed railway (HSR). By leveraging authors' continued endeavours, an SHM framework, based on actively generated diffuse ultrasonic waves (DUWs) and a benchmark-free condition contrast algorithm, has been developed and deployed via an all-in-one SHM system. Miniaturized lead zirconate titanate (PZT) wafers are utilized to generate and acquire DUWs in long-range railway tracks. Fatigue cracks in the tracks show unique contact behaviours under different conditions of external loads and further disturb DUW propagation. By contrast DUW propagation traits, fatigue cracks in railway tracks can be characterised quantitatively and the holistic health status of the tracks can be evaluated in a real-time manner. Compared with GUW- or AE-based methods, the DUW-driven inspection philosophy exhibits immunity to ambient noise and measurement uncertainty, less dependence on baseline signals, use of significantly reduced number of transducers, and high robustness in atrocious engineering conditions. Conformance tests are performed on HSR tracks, in which the evolution of fatigue damage is monitored continuously and quantitatively, demonstrating effectiveness, adaptability, reliability and robustness of DUW-driven SHM towards HSR applications.

Fractal analysis of high speed rail geometry data: A case study of Ankara-Eskişehir high speed rail

Abstract By considering railway track geometry as a fractal pattern, the irregularity of the track geometry can be expressed numerically with the help of fractal dimensions. In this study, a novel algorithm based on ruler method has been developed and a program was written to determine the fractal dimensions of railway track geometry graphs. Four different fractal dimensions of DR1, DR2, DR3, and DR4 were proposed to determine the geometric irregularity of the railway track by using the data of Ankara-Eskisehir High-Speed Railway track. DR1 and DR2 were used to quantify short wavelength irregularities while DR3 and DR4 were used to quantify medium wavelength irregularities. At the end of the study, the relationship between fractal dimensions and standard deviation values, which is the quality indicator according to EN 13848-6, was investigated. According to this, there is a strong relationship between the DR3 and the standard deviation.

Discrete element simulation of coupled vibration of high speed railway track under load

Discrete element simulation of coupled vibration of high speed railway track under load

Global Registration of Terrestrial Laser Scanner Point Clouds Using Plane-to-Plane Correspondences

Registration of point clouds is a central problem in many mapping and monitoring applications, such as outdoor and indoor mapping, high-speed railway track inspection, heritage documentation, building information modeling, and others. However, ensuring the global consistency of the registration is still a challenging task when there are multiple point clouds because the different scans should be transformed into a common coordinate frame. The aim of this paper is the registration of multiple terrestrial laser scanner point clouds. We present a plane-based matching algorithm to find plane-to-plane correspondences using a new parametrization based on complex numbers. The multiplication of complex numbers is based on analysis of the quadrants to avoid the ambiguity in the calculation of the rotation angle formed between normal vectors of adjacent planes. As a matching step may contain several matrix operations, our strategy is applied to reduce the number of mathematical operations. We also design a novel method for global refinement of terrestrial laser scanner data based on plane-to-plane correspondences. The rotation parameters are globally refined using operations of quaternion multiplication, while the translation parameters are refined using the parameters of planes. The global refinement is done non-iteratively. The experimental results show that the proposed plane-based matching algorithm efficiently finds plane correspondences in partial overlapping scans providing approximate values for the global registration, and indicate that an accuracy better than 8 cm can be achieved by using our global fine plane-to-plane registration method.

The nonlinear dynamical analysis of damaged concrete slab of high speed railway track using the revised Fourier pseudo-spectral method

A revised Fourier pseudo-spectral method is applied to quickly solve the dynamic response of the railway ballastless track structure with damage. Considering the nonlinearity of the material damage of the track slab and the base, the pseudo-spectral method (PSM) of collocation format is used to discretize the vibration equation of the track slab and the base in spatial domain. Since the convergence and solution precision of the collocation method are greatly related to the collocation scheme, in order to ensure the quasi-convergence of the pseudo-spectral method, the Fourier-Galerkin spectral method is used to obtain the elastic convergence solution of the periodic dynamic model of the ballastless track, which is used as the criterion for quasi-convergence of the approximate solution of PSM. In order to reduce the number of collocation points and improve the accuracy of the approximate solution of PSM, the ballastless track model with discrete point support is replaced by the ballastless track model with uniformly continuous support. The optimal number of collocation points for the quasi-convergence of the PSM is obtained. Then, the interpolation basis function of the PSM is regularized, and the modified PSM is proposed, with which the model can achieve quasi-convergence under given collocation point number. In this paper, the accuracy of the pseudo-spectral method is improved, and the principle of collocation point selection is established, which makes it feasible for the nonlinear periodic spectral method to be applied to the damage evolution analysis, life prediction and structural dynamic optimization of the ballastless track.

High speed railway ground dynamics: a multi-model analysis

ABSTRACT High speed railway track and earthwork structures experience varied levels of displacement amplification depending upon train speed. Protecting against amplified track deflections is challenging due to the complexity of deep wave propagation within both the track and supporting soil structures. Therefore it is challenging to derive design guidelines that encompass the full range of influential variables. As a solution, this paper uses a novel multi-model framework where 4 complimentary modelling strategies are combined, and thus able to generate new insights into railway ground dynamics and ‘critical velocity’. The four types of model are: 1) analytical, 2) hybrid analytical-numerical, 3) 2.5D numerical, 4) 3D numerical. They are used to explore subgrade layering, track type, train type, soil non-linearity, shakedown and ground improvement. The findings provide new insights into railway track-ground geodynamics and are useful when considering the design or upgrade of railroad lines.

Experimental and Numerical Investigation on Repairing Effect of Polymer Grouting for Settlement of High-Speed Railway Unballasted Track

Uneven settlement of high-speed railway subgrade leads to the irregularity of high-speed railway line, which seriously affects high-speed train operation. The skylight point of high-speed railway operation is short and the maintenance time is limited. Therefore, how to quickly lift and repair the ballastless track slab in the subsidence section is an urgent problem to be solved in the maintenance of high-speed railways. The two-component non-aqueous reactive polymer material has the advantages of strong expansive force, fast reaction speed, and wide application range, which is extremely suitable for the repair of high-speed railway track slab subsidence and lifting. In this study, the expansion force characteristics of different density polymer materials and the stress-deformation curves at corresponding density are tested in laboratory to propose the mechanical parameters of polymer. Then, a three-dimensional finite element (FE) model of high-speed railway train ballastless-track subgrade is established based on ABAQUS. The mechanical characteristics of CRTS III ballastless track under different repair materials, different elevation, and different density of polymer grouting materials are analyzed. The results show that, under the dynamic load of the train, the stress value of polymer repairing material is less than that of cement slurry, presenting a compressive stress state, which is similar to that of the complete subgrade surface. In addition, within a certain thickness range, increasing the thickness of polymer is beneficial to reducing the difference of stress variation between polymer filling layer and complete pavement. Once beyond this range, the thickness of polymer has little effect on the force variation.

Microstructure and Hydraulic Properties of Coarse-Grained Subgrade Soil Used in High-Speed Railway at Various Compaction Degrees

AbstractThis study presents an experimental investigation on the microstructure and the hydraulic properties of a coarse-grained soil used in high-speed railway track bed at various compaction degr...

Impact Responses of the Highspeed Railway Track Slabs

Impact loads pose a lot of hazards including causing severe damage to both railcars and rail track components, for example, cracking of slabs or sleepers. The impact loads can be as a result of several factors including flat spots on rail wheels attributed to the train braking, dipped rails, rail squats, corrugation, crossing transfers, etc. The impact loads are often over a short duration but of very high magnitude. For instance, the typical loading duration produced by wheel flats is about 1-10 milliseconds, while the force magnitude can be over 400 kN per rail seat. This paper highlights an investigation into the behaviour of a slab-track subjected to impact loading. A parametric study has been carried out using the finite element analysis software, Strand7, to investigate the behaviour of slab-track under the action of the impact loading conditions. This was done by analysing the ratio of maximum impact moment to maximum static force under varying slab support conditions. The outcome of this study will potentially lead to a better understanding and hence, the design of slab track systems in highspeed railway tracks subjected to the impact loading. Our study revealed that for a slab-track under the action of impact loading, the slab-track is more sensitive to changes in the support stiffness at midspan than at the rail seats and effects of increasing or reducing support stiffness are more significant at these locations.

Modeling of multi-sensor tightly aided BDS triple-frequency precise point positioning and initial assessments

The BeiDou global navigation satellite system (BDS), which is the first satellite navigation system that provides triple-frequency signals on B1, B2, and B3 for civil applications, has been applied widely around the Asian-Pacifica region. The current BDS precise point positioning (PPP) approaches are mainly based on the B1&B2 dual-frequency observations. To make full use of BDS’ triple-frequency observations, the motion sensors measurements, and the platform motion information, this paper proposes an inertial sensor, odometer, and heading measurement tightly aided BDS triple-frequency PPP model. In this model, inertial sensor biases, odometer scale factor, residuals of slant ionospheric delays, and inter-frequency code biases are estimated simultaneously in a unique extended Kalman filter. The Rauch-Tung-Striebel (RTS) smoother is further adopted to reduce the solution's noises and enhance the stability and relative measuring accuracy. To evaluate the capability of this method, a set of triple-frequency BDS raw observations, inertial measurements, odometer data, and heading measurements collected by a customized hardware system on Lanzhou-Urumqi high speed railway track in China, are processed and analyzed. Results illustrated that both positioning accuracy and cycle slip detection capability are upgraded significantly by applying B3 frequency observations in BDS PPP. About 13–55% position accuracy enhancements from B3 observations, inertial sensors, and RTS smoother, and over 70% heading improvements from the aids of heading measurements can be obtained. Moreover, such multi-sensor tight integration system can directly provide millimeter-level positioning accuracy in term of repeatability and provide sub-millimeter-level accuracy indirectly by transforming attitude solutions into distance solutions. Such accuracy is much higher than the state-of-art GNSS and such method presents potential capability in 3D geometry measuring.

Modelling and in-situ measurement of dynamic behavior of asphalt supporting layer in slab track system

During the last decades, asphalt concrete has been introduced in both ballast and ballastless track (including but not limited to slab track) systems. The use of asphalt concrete provides better damping and waterproofing performance. For this reason, a supporting layer of asphalt concrete (ASL) was introduced to the latest Chinese slab track system. In this paper, an in-depth study of the dynamic behavior of ASL was presented using modelling and in-situ measurement approaches. In the FE model, the train load was simplified to be a time series of concentrated load on rail nodes, and asphalt concrete was modeled as viscoelastic material by Prony series. The FE model was validated against in-situ measurement on a test section, in which a monitoring system was setup during construction. A series of transient analysis were conducted to obtain the dynamic responses of ASL under moving train load. The parametric effects of thickness of ASL was also studied with respect to the dynamic responses of superstructure and substructure, as well as the stability and durability of ASL. The results showed that, under moving bogie load, the reach of the dynamic responses in ASL is about 7.5 m in the longitudinal direction, and the maximum values occur at the position beneath the rails. A thicker ASL is more favorable to ride comfort and structural stability of high-speed railway track system. However, considering the economic and construction factors, an optimal thickness range of 7–10 cm is suggested for ASL in CRTS III slab track.