High-speed Track Research Articles

Wireless Monitoring of Ballastless Track Slab Deformation for High-Speed Railway

Ballastless slab track is the main form of ballastless track for the high-speed railway in the world. Deformation overrun of the track slab will seriously affect the smoothness of the track, and even lead to train safety accidents. The current practice mainly relies on manual periodic inspection, which is inefficient and cannot achieve continuous monitoring. Therefore, it is urgent to develop a real-time deformation monitoring solution for high-speed railway track slabs. This paper, based on multiple MEMs sensors, presents a multi-source sensor fusion and dynamic response analysis algorithm to identify the deformation mode of the track slab. Harvesting the vibration energy of the slab track instead of an electrochemical battery-only strategy could contribute to the achievement of carbon neutrality goals in the field of rail transit. Therefore, a self-contained system approach is developed for wireless monitoring of the track slab deformation. The deformation value of the track slab can be obtained with a monitoring resolution of <=1.5 mm, compliant with maintenance specifications for ballastless slab track deformation assessment (i.e., 1.5 mm for grade I threshold and 2 mm for grade II threshold). This work offers a new means for the safe operation and maintenance of high-speed railways and could also contribute to the realization of the strategic goal of the “dual-carbon project” in China.

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

Semi-automatic construction of pile-supported subgrade adjacent to existing railway

The rapid expansion of the high-speed railway network in China leads to an increasing number of connections between new constructed infrastructures and existing ones. The construction of the infrastructure extremely adjacent to existing high-speed railways significantly threaten the operation safety of the high-speed trains. To guarantee the operation safety of the existing high-speed railways in this sensitive zone, a developed Benoto pile-plank-supported subgrade and a set of specially designed construction equipment are proposed. A fiber-optical monitoring system for foundation deformation and structural internal forces is employed to provide a data basis for parameterization of the construction equipment. In this way, an integrated semi-automatic construction system is established. The application effect of the construction system is tested in a real construction project of a pile-supported subgrade adjacent to an existing high-speed railway track. In-situ measurement data reveal that the deformation of the existing high-speed railway subgrade can be well controlled.

Risk Assessment Method for High-Speed Railway Track Based on Dynamically Weighted Acceleration

AbstractAs railway maintenance increasingly requires strict inspection and accurate repair, it is urgent to establish a reasonable assessment method for identifying the risks in high-speed railways...

Full-scale test and numerical simulation of wheelset-gear box vibration excited by wheel polygon wear and track irregularity

The wheelset-gear box of high-speed train is the typical unsprung mass serving in the complex excitation environment. To investigate the independent and compounded influences of wheelset out-of-roundness, wheel polygon wear and track irregularity on the vibration performance of wheelset-gearbox system, the 1:1 high-frequency excitation test based on the rolling test rig is carried out within the speeds of 100 ∼ 500 km/h. The corresponding multi-body dynamic model is established and validated. The detailed wheel-wheel contact relations are discussed. The research results indicate that the test rig dynamic model can capture the vibration amplitude and main frequency characteristics well, especially for the vibration below 1000 Hz. For the wheelset-gearbox system without track excitation, its vibration energy is basically concentrated in the resonance region of test object. At higher speeds, the vibrations induced by wheelset and motor rotation gradually become dominant. Under excitation of the grinded polygon wear in rail wheel, the multiple-frequency vibration almost determines the system vibration level within the test speed ranges, whilst the vibration induced by the wheelset and motor rotation plays an important role only at the speed above 300 km/h. In comparison, the high-speed track random irregularity contributes very small vibration magnitude. For the axle box, the vibration amplitude composition ratios led by the excitations of wheelset out-of-roundness, rail wheel polygon wear and track irregularity are around 26.7%, 48.3% and 25% correspondingly. And for the gear box, the composition ratios reach 38.46%, 32.05% and 29.49% respectively. The wheel polygon wear has been the main excitation source in the high-frequency vibration of wheelset system, followed by the wheelset 1st-order out of round and track irregularity in sequence.

Stability of continuous welded rail on steel bridge subjected to thermal loading

Continuous Welded Rail (CWR) forms a smooth high-speed rail track. However, its stability has been a cause of worry for being a slender structural element and its tendency to buckle about the weaker axis. Track-Bridge Interaction (TBI) phenomenon results in additional axial rail stress, creating local high-stress zones in the track. Since TBI is the main reason for rail stress and track displacements of CWR on railway bridges, more confidence needs to be developed by quantifying the stability of CWR-on-bridge. In this study, a simplified numerical model is proposed to study the effect of TBI on the stability of CWR-on-bridge due to temperature loading. Boundary elements are utilized to reduce the number of elements in the model. The model predicts the state of the stress in CWR due to thermal loading. Stability analysis of CWR on a single span bridge employing nonlinear buckling analysis reveals a significant influence of TBI on CWR stability. The two critical buckling parameters of CWR, the maximum buckling temperature (Tmax) and safe temperature increase (Tmin), are affected by TBI. Tmin drops more rapidly compared to Tmax and needs to be kept below the safe limits to ensure track safety.

Impact of Rail Fastener Looseness on Vertical Dynamic Responses of High-Speed Vehicle and Ballastless Track

The fastener system is an essential component of the high-speed ballastless track system. A detailed analysis for the effect of fastener looseness on the vertical dynamic response of the vehicle–track coupling system is conducted from the time domain, frequency domain and time–frequency domain in this paper. A fine fastener system model is employed, which includes two spring rods and one rail pad. The preloaded force is proposed to simulate the defect of the fastener, and a looseness coefficient is defined to represent the loose degree of the fastener. First, three fastener system models are introduced into the model, respectively, and the difference in the vehicle–track dynamic is analyzed and compared. The results show that the proposed model is more consistent with the real situation and more suitable to simulate fastener defects. Then, the detailed analysis of vehicle and track dynamic responses is explored in the case of different degrees of loose fasteners and the case of completely loose fasteners. According to the simulation results, there is little impact on the dynamic response of the vehicle–track system when the looseness coefficient is less than 0.9. When the fasteners are completely loosened, the dynamic response of the wheelset and the rail significantly increases. The vibration responses of rail and wheelset enhance with the increase of the number of the completely loose fastener. The loose fasteners affect the low-frequency part of the wheelset vibration response and the high-frequency part of the rail vibration response. Finally, a time–frequency analysis method is used to analyze the system vibration response under the combined effect of the completely loose fastener and the track irregularity. The track irregularity still dominates the excitation of the system, and the vibration response of the wheelset and the rail is more sensitive to the fastener defect at low speed.

A robust method of the status monitoring of catenary poles installed along high-speed electrified train tracks

Electric trains are considered one of the most eco-friendly and safest means of transportation. Catenary poles are used worldwide to support overhead power lines for electric trains. The performance of the catenary poles has an extensive influence on the integrity of the train systems and, consequently, the connected human services. It became a must nowadays to develop SHM systems that provide the instantaneous status of catenary poles in-service, making the decision-making processes to keep or repair the damaged poles more feasible. This study develops a data-driven, model-free approach for status monitoring of cantilever structures, focusing on prestressed, spun-cast ultrahigh-strength concrete catenary poles installed along high-speed train tracks. The proposed approach evaluates multiple damage features in an unfied damage index, which leads to straightforward interpretation and comparison of the output. Besides, it distinguishes between multiple damage scenarios of the poles, either the ones caused by material degradation of the concrete or by the cracks that can be propagated during the life span of the given structure. Moreover, using a logistic function to classify the integrity of structure avoids the expensive learning step in the existing damage detection approaches, namely, using the modern machine and deep learning methods. The findings of this study look very promising when applied to other types of cantilever structures, such as the poles that support the power transmission lines, antenna masts, chimneys, and wind turbines.

Multiobjective Railway Alignment Optimization Using Ballastless Track and Reduced Cross-Section in Tunnel

The increasing need for railway planning and design to connect growing cities in inland mountainous areas has pushed engineering efforts toward the research of railway tracks that must comply with more restrictive constraints. In this study, a multiobjective alignment optimization (HAO), commonly used for highway projects, was carried out to identify a better solution for constructing a high-speed railway track considering technical and economic feasibilities. Then, two different and innovative scenarios were investigated: an unconventional ballastless superstructure, which is more environment-friendly than a gravel superstructure, and a reduced cross-section in a tunnel, which enables a slower design speed and then, less restrictive geometric constraints and earthmoving. The results showed that the first solution obtained a better performance with a slight increase in cost. Moreover, both scenarios improved the preliminary alignment optimization, reducing the overall cost by 11% for the first scenario and 20% for the second one.

Evaluation Index of CRTS III Prefabricated Slab Track Cracking Condition Based on Interval AHP

The cracking damage of the high-speed railway slab track seriously affects its durability and service life. The cracking condition index (CCI) for the China railway track system (CRTS) III prefabricated slab track and the corresponding calculation methods were proposed to realize the scientific management and guide the maintenance more reasonably. In order to ensure the objectivity and rationality of each parameter’s weight, first, the finite-element (FE) model of CRTS III prefabricated slab track with surface cracks was established to analyze the crack growth behavior, based on the fracture mechanics theory. The results show that the crack growth rate of transverse cracks at the same depth is greater than that of longitudinal cracks and significantly greater than that of through cracks. Then 437 valid questionnaires were obtained through expert consultation. Combining the subjective factors of expert evaluation with the objective factors of numerical simulation, the Delphi method and interval analytic hierarchy process (AHP) were used to establish the structural hierarchy, which could determine the weight of each parameter. After that, it was applied to an engineering example. The results show that the weights obtained by the comprehensive method combining the Delphi method and the interval AHP are more objective. Furthermore, the evaluation method was applied to the engineering example, obtaining the slab track CCI within [70.91, 72.83] points, which verified the rationality of the evaluation method. In short, the index evaluation method can quantitatively analyze the cracking severity of the track slab, which has important reference and practical value for line maintenance.

Design and Test of Composite Relative Position Sensor for High-Speed Maglev Track Measurement System

A composite relative position sensor is studied in this paper. The sensor outputs square signal corresponding to the cogging cycle of long stator track, which is used as the spatial sampling pulse for high-speed maglev track measurement system, and also provides relative position, speed and direction information. The sensor uses only one group of detection coils to identify the cog and two photoelectric switches to identify the direction, thus effectively reducing the mass and size of the sensor. To make sure the sensor works normally when it vibrates vertically and passes through the track joint, the processing methods are given respectively. The factors that affect the dynamic response characteristics are analyzed and compared, it is considered that the discharge time constant of the demodulation has a great influence, and based on this, the detection speed limit of the sensor is calculated as 253km/h. The dynamic test is carried out by using the equivalent inductance method, and the results show that the sensor can respond normally and output the results correctly within the speed of 200km/h. In addition, it is demonstrated that the sensor can detect accurately within a detection distance of 22mm and a lateral deviation of ± 22mm through platform test.

Assessment of the Selection of Asphalt Binder for Full Cross-Section Asphalt Waterproof Layer in High-Speed Railway Ballastless Track

AbstractIn China, the application of asphalt layers in high-speed railway ballastless tracks has two functions. Asphalt layers can be used as a support layer or a waterproof layer; one of these fun...

SHM deformation monitoring for high-speed rail track slabs and Bayesian change point detection for the measurements

Fiber Bragg grating (FBG) technology has significant advantages in anti-electromagnetic interference and is suitable for structural health monitoring (SHM) in high-speed rail (HSR). In this paper, a deformation monitoring system based on FBG technology is designed for HSR track slab. Regarding to the possible large deformation of the track slab, a Bayesian change point detection (CPD) method is adopted to detect change points of the monitoring data sequence and the posterior probability distribution of change points can also be derived. The Bayesian CPD algorithm can directly sample and simulate from the posterior probability distribution of change point to determine corresponding parameters of regression model, as well as yielding uncertainty evaluation. The designed SHM system was implemented on a segment of HSR track on the Lanzhou-Xinjiang line in China to carry out the measurement of track slab deformation. Results shows that the designed SHM can resist strong electromagnetic interference in the operation environment of high-speed rail and versine deformation monitoring data over two months for the target track segment can be extracted based on SHM measurement. Through posterior distribution information of the Bayesian CPD method, change points which have the highest posterior probability can be identified for the versine deformation of HSR track slabs, which is essential for investigating the cause of the change point and providing maintenance plan in time.

The Design and Implementation of an Inertial GNSS Odometer Integrated Navigation System Based on a Federated Kalman Filter for High-Speed Railway Track Inspection

The detection of track geometry parameters is essential for the safety of high-speed railway operation. To improve the accuracy and efficiency of the state detector of track geometry parameters, in this study we propose an inertial GNSS odometer integrated navigation system based on the federated Kalman, and a corresponding inertial track measurement system was also developed. This paper systematically introduces the construction process for the Kalman filter and data smoothing algorithm based on forward filtering and reverse smoothing. The engineering results show that the measurement accuracy of the track geometry parameters was better than 0.2 mm, and the detection speed was about 3 km/h. Thus, compared with the traditional Kalman filter method, the proposed design improved the measurement accuracy and met the requirements for the detection of geometric parameters of high-speed railway tracks.

Robust efficient cruise control for high-speed train movement based on the self-triggered mechanism

This paper investigates the robust efficient self-triggered cruise control problem for high-speed trains to reduce the consumptions of the computational resources and wireless communication bandwidth. By capturing the dynamic evolution of high-speed trains in the actual environment, an error dynamic state-space model is established considering uncertain parameters, input constraints and disturbances to the train motion. According to the event-triggered control framework, a co-design method is introduced to design the cruise controller and the event-triggered condition jointly. Based on the Lyapunov stability method, a sufficient condition for the existence of the robust state-feedback control law and the event-triggered condition parameter are presented in terms of linear matrix inequalities (LMIs), which ensures that the high-speed train tracks the desired speed, and the coupler deviations are stable at the equilibrium point under external disturbances. With the fact that the event-triggered controller often requires a dedicated detector to continuously monitor the system state, a self-triggered implementation is further developed to dynamically calculate the next triggered instant at each update time based on recently collected information. In the end, numerical experiments are provided to illustrate the effectiveness of the proposed approach in tracking the desired movement profiles, and thereby demonstrates the advantages of the proposed self-triggered controller over the traditional periodic triggered control method.

The optimum model determination of porous barriers in high-speed tracks

In the railway industry, safety is an essential factor that has been modified by all societies and railroad managers. Against the background of increasing speed of rolling stock, risk factors such as cross wind and train stability have received more extensive attention. In this study, the porous wind barriers that are widely used in this industry have been surveyed. Also, to decrease the harmful effects of crosswind, the work attempts to find an optimum porous barrier design. This numerical simulation was based on a modern computational fluid dynamic in microscopic space model called the Lattice Boltzmann Method. Also, to find the optimum type of barrier design, the Multi-Objective Genetic Algorithm had been used. Two aspects of barrier design, including the porosity levels and distance between barriers, have been studied and, finally, a candidate design proposed for the barriers. It was found that porousity levels up to 15% have a positive effect in reducing the lift force coefficient, but beyond that it has a negative effect. On the other hand, increasing the porosity level leads to a decrease in the drag coefficient. The velocity vectors, velocity counter, vorticity, and turbulence intensity of the flow field around the model plotted for the candidate barrier.

Predicting Mechanical State of High-Speed Railway Elevated Station Track System Using a Hybrid Prediction Model

Elevated station track system is one of the most vulnerable parts in high-speed railway and prone to various defects during long-term service. The structural mechanical state will be deteriorated with the occurrence of defects, which will finally threaten the operation. Therefore, it is essential to monitor and accurately predict the structural mechanical state of elevated station track system. However, the existing prediction methods cannot achieve an accurate prediction of the structural mechanical state of the elevated station track system. Aiming at the problem, a hybrid model integrating wavelet transform, convolutional neural network, and long-term memory was proposed, which has the best performance compared with state-of-art methods and can be expanded to the state prediction of civil infrastructures. The prediction method can pre-evaluate the structural state, guide timely maintenance, and contribute to the safety of the high-speed railway.

Advanced full-scale laboratory dynamic load testing of a ballasted high-speed railway track

Understanding ballast layer dynamic response and long-term behavior under moving train loads is necessary for optimization of railway track performance. This paper discussed an advanced testing effort undertaken in a controlled laboratory environment for the measurement of dynamic load responses via multitude of installed sensors and the development of validated computer models and simulation tools suitable for analyzing full-scale ballasted track under dynamic loading. Constructed in a large rectangular metal frame, the laboratory model consisted of a full-scale track with eight ties, ballast, subballast, and embankment. Three different speeds and axle load configurations were applied sequentially onto the full-scale ballasted track using eight actuators, which realistically captured both slow moving freight and high-speed passenger train loads. Vibration velocities were captured at different locations on ballast surfaces and ties. Dynamic soil stresses were recorded at the bottom of the ballast and subballast layers. Both transient and permanent deformations due to repeated dynamic loads were measured in the track substructure layers and for all eight ties. “SmartRock” advanced sensors were used for the first time to track ballast particle movements under dynamic loading. Further, the test data from the experiments were compared with preliminary Discrete Element Method (DEM) simulations.

Vibro-fluidization of sand under coupled static loading and high-frequency cyclic loading

An increase in the operation speed of high-speed trains often leads to an increase in the loading frequency on subgrade soil. Hence, the long-term dynamic behavior of the subgrade and the service performance of high-speed tracks are affected. To determine the stress–strain characteristics of granular soil under high-frequency loading, a triaxial test setup was modified to investigate the effects of loading acceleration and duration, water content, vibration frequency, cell pressure, and initial soil density. The experimental results indicate that there are reductions in axial stress and volumetric strain during high-frequency loading. The reduction in axial stress is as high as 40%, and that of volumetric strain, which is permanent, could approach 0.1%. The stress reduction, strain compression, and excess pore pressure are found to vary linearly with vibration acceleration when a/g &gt; 0.02, where a is vertical vibration acceleration and g is gravitational acceleration. The reduction in strength and strains are found to depend on the loading acceleration and effective cell pressure, but independent of the loading duration, water content, frequency, and initial density. A threshold acceleration a = 0.02g is observed, below which the changes in the shear strength and volumetric strain induced by vibration are negligible. At high vibration acceleration, the strain amplitude could increase, eventually leading to a collapse of the specimen.

Static Strain Analysis of CRTS I Bi-Block Ballastless Track

In this paper, relying on the National Engineering Laboratory of High-Speed Railway Construction Technology, a full-scale model of the double-block ballastless track structure is established, and the strain analysis of the layered track structure under different static loads is carried out, which has a certain practical significance for the design and maintenance of the high-speed railway ballastless track in our country. Research conclusion: (1) Under the action of static load, the sleeper directly under the rail is under compression; the four corners of the sleeper are tensile strain; (2) The strain at each measuring point on the surface of the track slab around the sleeper is compressive strain; the edge of the top surface of the track slab is compressive strain; The longitudinal strain at the bottom of the side of the track slab is tensile strain; (3) Under static load, the longitudinal strain measurement point on the top surface of the base plate is tensile strain at a distance of two sleepers from the static load position; the longitudinal strain at the bottom of the side of the base plate is tensile strain.