Operation Of High-speed Railway Research Articles

Research on Ultrasonic Guided Wave Technology for the Rail Fatigue Cracks Based on PCA-adaboost.M2 Algorithm

Abstract As a key equipment in high-speed railway operation, rails inevitably produce various fatigue cracks during long-term service, which are major safety hazards in the railway transportation. In order to achieve intelligent detection of the rail fatigue cracks, the PCA-adaboost.M2 algorithm based on ultrasonic guided waves is proposed for the classification and identification of rail fatigue cracks. First, a rail fatigue crack detection system based on an ultrasonic guided wave was established to obtain ultrasonic guided wave signals at different depths of the rail fatigue cracks. Then, five time–frequency domain features of the ultrasonic guided wave (the maximum, the mean, the variance, the center of gravity frequency, and the frequency variance) were extracted, and the five main components of the ultrasonic guided wave were extracted by the principal component analysis (PCA) method and are used for classification and recognition of the adaboost and the adaboost.M2 algorithm, separately. The experimental results show that the ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed has good performance in quantitative detection of the rail fatigue crack depth. The ultrasonic guided wave based on the PCA-adaboost.M2 algorithm proposed in this paper provides a method for detecting the rail fatigue crack depth.

Numerical analysis of dropper stress under a moving load based on the uplift displacement for a high-speed railway

<abstract> <p>The most essential cause of the fracture of the dropper is the effect of alternating stress for a long time. Therefore, in order to ensure the safe operation of high-speed railways, the influence of moving loads on the stress of a dropper was investigated in this study. Due to a high-voltage catenary system, it is very difficult to measure the moving load. Thus, the uplift displacement measured by some software and hardware devices has been applied to the contact wire instead of the moving load. The response equation for the contact wire has been derived so as to determine the initial and boundary conditions of each dropper. Then it was combined with the equation for vibration analysis of the dropper and the stress of each dropper was calculated by using the finite-difference method based on a written MATLAB program. The results show that the dropper stress, during a certain period goes through two stages of immediate rebound and bending compression when the uplift displacement is large. After the pantograph passes, the vibration of the dropper tends to be smooth; also, dropper stress variation with timecan be described by three stages: immediate rebound, vibration attenuation, and bending compression. In addition, the maximum tensile stress of dropper Ⅳ was the highest. It indicates that dropper Ⅳ was more prone to fracture than other droppers.</p> </abstract>

Spatiotemporal Heterogeneity of Carbon Dioxide Emissions: Evidence from High-Speed Railway Operations in China

Carbon dioxide (CO2) emissions reduction has become an ever-growing concern in China and the government has proposed the goals of carbon peak and carbon neutrality. To better address this concern, this work pays particular attention to high-speed railway (HSR) operations and examines their spatiotemporal effects and potential mechanism on CO2 emissions. Using a geographically and temporally weighted regression (GTWR) model to fit a balanced panel dataset from the period 2008 to 2018, we have the following main findings. First, the GTWR model performs better than the pooled panel regression model as it considers temporal and spatial variations in factors of CO2 emissions simultaneously. Second, the temporally varying coefficients of HSR operations indicate their consistent contributions to emissions reduction, suggesting that the national development of HSRs can provide significant emissions reduction benefits. Third, as revealed by the spatially varying coefficients of HSR operations, most provinces can mitigate CO2 emissions by promoting HSRs, particularly in Shanxi, Hebei, and Shaanxi, owing to the larger contributions of HSR operations to CO2 emissions reduction. Finally, the contributions of HSR operations to emissions reduction can be transmitted through the mechanism of technological progress. These findings can offer valuable insights into cross-collaborative and province-specific policymaking for mitigating CO2 emissions.

The influence of uneven frost heave and thermal conditions on the deformation and damage of slab track in seasonally frozen regions

To ensure the secure operation of high-speed trains in seasonally frozen regions, this paper investigates the deformation and failure patterns of slab tracks subjected to uneven frost heave and environmental issues. Utilizing our team’s previous research findings, finite element analysis software was employed to construct a mechanical transfer calculation model for the subgrade and slab track. This model was used to explore the relationship between uneven frost heave and slab track deformation at different time periods, along with the track structure’s damage behavior. In addition, comprehensive temperature field tests were conducted on the China railway track system (CRTS) III slab track, probing temperature variations, warping deformations, and stress distributions within the track structure. Finally, the interaction of uneven frost heave and thermal loads unveiled the interlayer debonding and stress characteristics of slab track structures across different months in seasonally frozen regions. The results revealed that the greater amplitude of frost heave and the smaller wavelength led to a higher change rate of rail irregularity. The uneven lateral deformation of the subgrade surface due to the sunny-shady slopes effect resulted in significant rail level irregularity of slab tracks. The combined impact of short-wavelength frost heave and temperature gradient loads emerged as the primary cause of macroscopic damage and stiffness degradation of concrete materials within slab track structures. These findings will help to understand the mechanical behavior of slab tracks in cold regions, thereby improving the quality of high-speed railway operations.

Study on the splashing behavior of high-speed railway ballast in ice and snow environment: Analysis of the influence of the train speed, ice mass and striking position

The snow flight in severe cold regions has occurred on many high-speed railway lines in China, directly impacting the safety of high-speed railway operations. However, the research on this problem has not been carried out systematically at present, and the establishment of the theoretical simulation model remains blank. In this paper, the DEM-MBD-CFD coupling analysis method is used to build a refined simulation model of snow flight on high-speed train-ballasted track, which reproduces the actual scenes of three typical cases where the snow flight hits the train body and verifies the reliability of the model with field test results. The results show that the wind pressure amplitude at the center of the ballast bed is the largest, the bottom of the rail is the second largest, and the shoulder of the ballast is the smallest. After the ballast particles fly away from the ballast bed, the main power source is the negative pressure generated by the train’s airflow field. The number of flying ballast particles and the impact force on the train floor grow with the increase of train speed. When the train speed increases to 400 km/h, the average impact force increases to 12.76 kN, which is approximately 8.7 times the impact force at 250 km/h. With the increase of ice mass, the impact stress first increases rapidly and then slowly. When the ice mass is 7 kg, the impact stress has exceeded the yield strength of the train body, seriously affecting the safety of the operation. Many prevention measures, such as reducing the operation speed, implementing ice and snow removal, installing anti-splash coating and grille, and optimizing the structure design, can be taken to reduce the damage of snow flight.

Evaluating the Safety and Control Scheme of Coastal Railway Using Land Subsidence Coupling Model

Uneven settlement caused by excessive exploitation of groundwater will seriously affect the smooth operation of high-speed railways. This study takes the Jinwei high-speed railway as an example to explore the development characteristics and distribution of groundwater and land subsidence along the railway under the influence of groundwater exploitation. Based on the comprehensive analysis of hydrogeological conditions and soil characteristics, a three-dimensional coupling model of groundwater seepage and land subsidence was established. The groundwater flow field and land subsidence along the railway under different mining schemes were quantified, and the prevention and control scheme to ensure the smooth operation of the high-speed railway was determined. The results show that the coupling model verified by groundwater and subsidence monitoring data can better simulate the development process of land subsidence. The subsidence center along the railway line is located between DK315 ∼ DK327, with a predicted maximum subsidence rate of 16.36 mm/a. The second most serious area is located between DK295 ∼ DK309, with a maximum subsidence rate of 12.21 mm/a. The maximum ban on mining along the railway is extended to 350 m at the section DK295 ∼ DK309, and to 450 m at the section DK315 ∼ DK325, which can minimize the impact of land subsidence on the high-speed railway.

Robust IR–VIS image registration with different FOVs in railway intrusion detection

Perimeter intrusion is a fatal threat to high-speed railway operation safety. IR (Infrared) and VIS (Visible light) image fusion can significantly enhance detection performance. Image registration is the premise of fusion, but classical registration algorithms are not suitable for railway owing to different image modalities and resolutions, large FOV (Field of View) differences, and repetitive texture features. To overcome these challenges, a coarse-to-fine area-based image registration method with feature-based constraints is proposed. An image transform model just considering translation and scaling is presented to reduce registration parameters. An edge-map-based SSIM (Structural Similarity Index) is designed to measure transform model precision of multi-modal images. Corresponding rail vanishing point pair is firstly used for coarse registration to accelerate registration, then corresponding rail line pairs are applied for fine registration to obtain accurate registration. Sufficient experiments demonstrate that the proposed method can achieve accurate and robust image registration in railway with poor lighting and large FOV differences.

Fault Diagnosis of a Switch Machine to Prevent High-Speed Railway Accidents Combining Bi-Directional Long Short-Term Memory with the Multiple Learning Classification Based on Associations Model

The fault diagnosis of a switch machine is vital for high-speed railway operations because switch machines play an important role in the safe operation of high-speed railways, which often have faults because of their complicated working conditions. To improve the accuracy of turnout fault diagnosis for high-speed railways and prevent accidents from occurring, a combination of bi-directional long short-term memory (BiLSTM) with the multiple learning classification based on associations (MLCBA) model using the operation and maintenance text data of switch machines is proposed in this research. Due to the small probability of faults for a switch machine, it is difficult to form a diagnosis with the small amount of sample data, and more fault text features can be extracted with feedforward in a BiLSTM model. Then, the high-quality rules of the text data can be acquired by replacing the SoftMax classification with MLCBA in the output of the BiLSTM model. In this way, the identification of switch machine faults in a high-speed railway can be realized, and the experimental results show that the Accuracy and Recall of the fault diagnosis can reach 95.66% and 96.29%, respectively, as shown in the analysis of the ZYJ7 turnout fault text data of a Chinese railway bureau from five recent years. Therefore, the combined BiLSTM and MLCBA model can not only realize the accurate diagnosis of small-probability turnout faults but can also prevent high-speed railway accidents from occurring and ensure the safe operation of high-speed railways.

How does high-speed railway affect green technology innovation? A perspective of high-quality human capital

Green development is the main theme of modern development in China and even the world. Green development depends on green technology innovation (GTI). Therefore, for developing countries like China in the stage of economic transition, it is urgent to accelerate GTI to gain sustained advantages in the new round of international competition. As an important representative of contemporary rapid transportation, high-speed railway (HSR) can not only alleviate the rapidly growing transportation demand of the public, but also have potential benefits to the energy consumption structure and environmental quality. Whether and how HSR affects GTI has become the focus of this paper. Hence, by employing the panel data of 286 cities in China from 2007 to 2018 with the time-varying DID model, this paper verifies that HSR development can contribute to GTI. The main findings of this paper are as follows: (1) The operation of HSR can not only make the incremental development of GTI, but also improve the quality of GTI simultaneously. Moreover, the quality improvement effect of HSR is greater than the quantity increment effect. (2) Heterogeneity analysis shows that the positive effect of HSR on GTI is more significant for cities that have implemented LCCP. (3) This paper verifies the mediating effect of high-quality human capital. The opening of HSR further stimulates GTI by improving the level of high-quality human capital in cities and increasing the opportunities for knowledge exchange and diffusion. Based on the above findings, this paper proposes some policy recommendations to help developing countries achieve GTI with positive externalities.

Data assimilation of PS-InSAR vertical deformation into a frost heave model to analyze subgrade deformation of high-speed railway in northwest China

Temperature changes may cause irregular soil uplift or thawing settlements in frozen soil areas, potentially affecting the safe operation of High-Speed Railways (HSR). Analyzing and predicting these deformation characteristics is thus critical. However, the conventional forecasting and analysis techniques rarely considered factors such as dynamic parameter variations, uncertainties, and measurement errors, which hinder accurate regional scale forecasting. To bridge this gap, this paper introduces a novel time-series coupling method, which integrates post-processing deformation from Interferometric Synthetic Aperture Radar (InSAR) with a frost heave model (FHM), facilitated by the ensemble Kalman filter (EnKF) assimilation algorithm. We obtained deformation observations along the HSR using Persistent Scatterer InSAR (PS-InSAR) technology in combination with time-series post-processing techniques. Considering the causative factors for deformation, we structured the FHM. By integrating FHM with observational data using the EnKF algorithm achieved an efficient upgrade of the posterior distribution of model parameters. This integration significantly improves the predictive accuracy, it facilitates an efficient update to the posterior distribution of model parameters, leading to enhanced prediction accuracy of our model. Our experimental results indicate that the effectiveness of this approach, with observational data assimilation into FHM reducing the average Root Mean Square Error (RMSE) to a mere 0.247 mm. Concurrently, both the Normalized Reduction Error Index (NER) and the Assimilation Efficiency Factor (EFF) values surpassed 0.60 and 0.84 respectively. These underlines signify a successful update of our model parameters, which in turn elevates the accuracy of future deformation predictions, thereby promising safer railway operations.

An Automatic Train Operation Based Real-Time Rescheduling Model for High-Speed Railway

With the continuous development of the Automatic Train Operation (ATO) system in high-speed railways, automatic driving is progressively supplanting manual operations, ushering in a new era of predictability and reliability for high-speed railway transport. Concurrently, the advent of the ATO system provides a notable impact on real-time rescheduling during disruptions, as it equips dispatchers with precise insights into train operation statuses. This paper is dedicated to a thorough analysis of how the transition to automatic driving in train operations influences the real-time rescheduling model. Based on the distinctive impact of the ATO system on real-time rescheduling, we have proposed a mixed-integer linear programming model that combines train re-timing, reordering, and the minimization of passenger delays. To validate the effectiveness of our model, we present several experiments conducted using data from the Beijing–Shanghai high-speed railway line. The results unequivocally demonstrate that our ATO-based model significantly mitigates train delay time, demonstrating its practical value in optimizing high-speed railway operations.

Modeling and analysis of transition-point disappearance in high-speed railway pantograph-catenary system

During the operation of high-speed railway, the transition-point disappearance phenomenon, which is caused by the deformation of pantograph head, poses a safety threat to the pantograph-catenary system. In this study, the analytical model for transition-point disappearance analysis is presented. The instantaneous profile, as well as the deformation process of the pantograph head under different contact force values and positions or different pantograph-head parameters can be solved using the model. Curve equation, force analysis, coordinate axis rotation, and few other methods are adopted to achieve simplified modeling. The proposed modeling method and analysis conclusion provide theoretical support for the permissible contact force range calculation and pantograph-head parameters optimization to prevent transition-point disappearance. The effectiveness of the proposed model is verified using both finite element simulation and experimental measurements. Finally, a case analysis for the prevention of transition-point disappearance is conducted, using pantographs with the models CX-GI and DSA250 as examples.

Exceeding probability analysis for rail of high-speed railway under seismic excitations

PurposeThe smoothness of the high-speed railway (HSR) on the bridge may exceed the allowable standard when an earthquake causes vibrations for HSR bridges, which may threaten the safety of running trains. Indeed, few studies have evaluated the exceeding probability of rail displacement exceeding the allowable standard. The purposes of this article are to provide a method for investigating the exceeding probability of the rail displacement of HSRs under seismic excitation and to calculate the exceeding probability.Design/methodology/approachIn order to investigate the exceeding probability of the rail displacement under different seismic excitations, the workflow of analyzing the smoothness of the rail based on incremental dynamic analysis (IDA) is proposed, and the intensity measure and limit state for the exceeding probability analysis of HSRs are defined. Then a finite element model (FEM) of an assumed HSR track-bridge system is constructed, which comprises a five-span simply-supported girder bridge supporting a finite length CRTS II ballastless track. Under different seismic excitations, the seismic displacement response of the rail is calculated; the character of the rail displacement is analyzed; and the exceeding probability of the rail vertical displacement exceeding the allowable standard (2mm) is investigated.FindingsThe results show that: (1) The bridge-abutment joint position may form a step-like under seismic excitation, threatening the running safety of high-speed trains under seismic excitations, and the rail displacements at mid-span positions are bigger than that at other positions on the bridge. (2) The exceeding probability of rail displacement is up to about 44% when PGA = 0.01g, which is the level-five risk probability and can be described as 'very likely to happen'. (3) The exceeding probability of the rail at the mid-span positions is bigger than that above other positions of the bridge, and the mid-span positions of the track-bridge system above the bridge may be the most hazardous area for the running safety of trains under seismic excitation when high-speed trains run on bridges.Originality/valueThe work extends the seismic hazardous analysis of HSRs and would lead to a better understanding of the exceeding probability for the rail of HSRs under seismic excitations and better references for the alert of the HSR operation.

Effect of Groundwater Level Rise on the Critical Velocity of High-Speed Railway

The increasing frequency of extreme rainfall is leading to a rise in groundwater levels in coastal areas, significantly affecting high-speed railway operations. To address this concern, this study developed a 2.5-dimensional finite element model of a coupled track-embankment-ground system based on Biot’s porous media theory to analyze the effect of groundwater level rise on the critical velocity of high-speed railways and vibration responses. The findings reveal a consistent decrease in the critical velocity of high-speed railways with rising groundwater levels. Particularly, the increase in groundwater levels within the embankment significantly influences the critical velocity compared to a similar rise in the foundation’s groundwater level. Furthermore, deformations induced by passing trains significantly increase as groundwater levels rise. Specifically, when the groundwater level rises from the foundation bottom to the subgrade surface, subgrade surface deformation increases by approximately 55%. As trains approach the critical velocity, significant vibration phenomena, known as the “Mach effect,” occur at the foundation surface. Importantly, as groundwater levels rise, the “Mach effect” intensifies. Analyzing the vibrating frequency spectrum of the displacement response demonstrates a substantial increase in vibration amplitude, particularly in the high-frequency region, as groundwater levels rise. This study highlights that the rise in groundwater level not only amplifies vibrations but also extends the propagation of high-frequency vibrations, underscoring the importance of effective embankment waterproofing in controlling track vibrations.

The impacts of high-speed railway on environmental sustainability: quasi-experimental evidence from China

With growing concerns over resource depletion and environmental degradation, the role of high-speed railways in fostering a transition towards sustainable energy sources has gained prominence. Against this background, we treat the opening of high-speed railways as a quasi-natural study, analyze data from Chinese industrial enterprises and 285 prefecture-level cities to investigate the impact of high-speed railways on environmental sustainability, specifically focusing on fossil fuel consumption and carbon emissions. Our results unequivocally demonstrate that the introduction of high-speed railways has been instrumental in promoting eco-friendly development, as evidenced by a notable reduction in traditional resource consumption and carbon emissions along the railway routes. This inhibitory effect has strengthened over time and with increasing distance from the railway. Additionally, we identify significant spatial spillover and spatial conduction effects resulting from high-speed railway operations. Heterogeneity tests reveal that third-tier cities, non-megacities, and mature resource-based cities are particularly receptive to these sustainable impacts. Besides, Mechanism analysis suggests that accelerated elements flow, enhanced technological innovation, improved labor productivity, and upgrading of industrial structure serve as potential pathways leading to eco-sustainability. These findings highlight the environmentally friendly attributes of high-speed railways and underscore the pressing need for effective policy measures to facilitate a global transition towards renewable energy, both in China and worldwide.

Nondestructive determination of longitudinal rail stress from guided wave dispersion properties

The determination of the longitudinal stress in continuous welded rails is essential for the safe operation of high-speed railways. Guided wave inspections have many advantages, and can provide an effective tool for non-destructive measurements of the longitudinal stress in rails. This paper provides a new method for determining longitudinal rail stress using ultrasonic guided wave dispersion properties. First, the characteristic equations of guided waves propagating in a waveguide with existing longitudinal stress are constructed, generating the dispersion properties of the waveguide such as the wavenumber, phase velocity and group velocity. The sensitivity of the dispersion properties of propagative modes to the longitudinal rail stress is investigated, which is then used for selecting appropriate modes for guided wave inspections. On the basis of the perturbation method, the relationship between the change in longitudinal rail stress and the change in dispersion properties is developed, which can be used for determining the longitudinal rail stress from dispersion properties. Furthermore, a mode selection index considering both the stress sensitivity and mode shape characteristics is employed for selecting appropriate propagative modes for guide wave inspections. Finally, a numerical example for CHN60 rail is adopted to demonstrate the effectiveness of the proposed method. From the results, the proposed method can accurately determine the longitudinal stress in the rail by using the dispersion properties available.

Vibration energy transmission in high-speed train-track-bridge coupled systems

This paper investigates the vibration energy transmission characteristics of high-speed train-track-bridge coupled systems based on a high-speed railway in China. A coupled system composed of a CRH380A high-speed train, CRTS II slab ballastless track, and standard 32-meter girder bridge was analyzed through hybrid simulations that integrated multi-body dynamics and finite element analysis. The hybrid model included the interactions between the train, track, and bridge of the coupled system as well as track irregularity. The vibration energy of the coupled system was quantitatively investigated under various train velocities. The effects of key variables of ballastless track and bridge on energy transmission characteristics were evaluated. The studied variables included fastener stiffness, fastener damping, mortar layer stiffness, bridge cross section, and bridge damages. The results show that these variables have significant effects on vibration energy transmission, suggesting that it is important to consider these variables in the design and operation of high-speed railways.

An Integrated Optimization Method of High-Speed Railway Rescheduling Problem at the Network Level

For high-speed railway operations at the network level, unforeseen events that lead to operation interruptions are inevitable, which should be handled within a short period of time to reduce the influence of the events as much as possible. This paper introduces an integrated optimization method to deal with rescheduling problems at the railway network level under emergencies, rescheduling the train timetable, and utilizing the train sets. train set A three-objective optimization model is proposed with the aim of minimizing additional operation costs, total delay, and the number of transfer passengers. Then, an algorithm based on NSGA-III is proposed to solve the model. Computational experiments on real data are conducted to show the adaptability of the model and algorithm. The average optimization rate of the three objectives is 12.12%, 14.12%, and 10.57%, indicating the effectiveness of the method. Moreover, more experiments on a railway network in China are being conducted to analyze which section and which time have the greatest impact on the railway network when emergencies occur. According to the experiment, the bottleneck section is section 15, and the bottleneck time is 11:00 am. In addition, the importance of all the depots is discussed, and depot II is selected as the most important depot.

Mesoscale modelling of CRTS II slab tracks subjected to thermal action and vehicle loads

Evaluation of the damage and deformation of cast-in-situ concrete joints between the precast concrete track slabs of the China Railway Track System (CRTS) II is crucial to the safe operation of high-speed railways. To investigate the damage and deformation evolution of concrete joints under thermal action (caused by the natural meteorological environment) and vehicle loads, a two-dimensional thermal–mechanical coupled numerical model of concrete joints at the mesoscale was developed. This model analyses the influence of three factors – concrete strength, maximum diameter of the joint concrete aggregate and vehicle speed. First, meteorology and heat transfer theory were used in thermal simulations. Then, the non-linear characteristics of the joint concrete were modelled as a two-phase composite material based on the random aggregate algorithm and strain-based elastic damage theory at the mesoscale. The cohesive zone model was used to simulate the interfaces between precast slabs. The reliability of the proposed model was assessed using field measurements. The results of a numerical example showed that the maximum aggregate diameter of the joint concrete significantly affected damage evolution in the joint concrete and concrete strength has a slight effect on joint uplift.

Land Subsidence Prediction and Analysis along Typical High-Speed Railways in the Beijing–Tianjin–Hebei Plain Area

High-speed railways in the Beijing–Tianjin–Hebei (BTH) Plain are gradually becoming more widespread, covering a greater area. The operational safety of high-speed railways is influenced by the continuous development of land subsidence. It is necessary to predict the subsidence along the high-speed railways; thus, this work is of critical importance to the safety of high-speed railway operation. In this study, we processed Sentinel-1A data using the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique to acquire the land subsidence in the typical BTH area. Then, we combined the Empirical Mode Decomposition (EMD) and Gradient Boosting Decision Tree (GBDT) methods (EMD-GBDT) to forecast land subsidence along high-speed railways. The results revealed that some parts of the high-speed railways in the BTH plain had passed through or approached the land subsidence area; the maximum cumulative subsidence of the Beijing–Shanghai, Tianjin–Baoding and Shijiazhuang–Jinan high-speed railways reached 326 mm, 384 mm and 350 mm, respectively. The forecasting accuracy for land subsidence along high-speed railways was enhanced by the EMD-GBDT model. The Root Mean Square Error (RMSE) and Mean Absolute Error (MAE) were 0.38 mm to 0.56 mm and 0.23 mm to 0.38 mm, respectively.