Within the SILVARSTAR project, a user-friendly frequency-based hybrid prediction tool has been developed to assess the environmental impact of railway-induced vibration. This tool is integrated in existing noise mapping software. Following modern vibration standards and guidelines, the vibration velocity level in a building in each frequency band is expressed as the sum of a force density (source term), line source transfer mobility (propagation term) and building correction factor (receiver term). A hybrid approach is used that allows for a combination of experimental data and numerical predictions, providing increased flexibility and applicability. The train and track properties can be selected from a database or entered as numerical values. The user can select soil impedance and transfer functions from a database, pre-computed for a wide range of parameters with state-of-the-art models. An experimental database of force densities, transfer functions, free field vibration and input parameters is also provided. The building response is estimated by means of building correction factors. Assumptions within the modelling approach are made to reduce computation time but these can influence prediction accuracy; this is quantified for the case of a nominal intercity train running at different speeds on a ballasted track supported by homogeneous soil of varying stiffness. The paper focuses on the influence of these parameters on the compliance of the track–soil system and the free field response. We also demonstrate the use and discuss the validation of the vibration prediction tool for the case of a high-speed train running on a ballasted track in Lincent (Belgium).
Track irregularity from rail alternate side wear is manifested as uneven rail wear waveforms alternating in the left and right rails with equal intervals, which will cause carbody sway behaviour of railway vehicles and greatly influences the passenger comfort. In this work, the carbody sway behaviour and mechanism due to track irregularity from rail alternate side wear and possible solutions to this issue were studied by the field testing and numerical calculation approaches. First, the carbody sway of an urban rail transit train is introduced with full-scale field tests, through which the rail alternate side wear is characterized and the formatted track irregularity are presented. Then, multibody vehicle dynamic models are developed to reproduce the carbody sway behaviour induced by the track irregularity from the rail alternate side wear. The creep forces acting on the wheel and rail are preliminarily discussed to study the influence of the carbody sway on the wear of the wheel flange and the rail corner. Finally, some potential solutions, e.g. improving the damping ratio of carbody rigid mode and rail grinding, are proposed to relieve this issue. It is concluded that an increased damping ratio of the carbody mode can alleviate the carbody sway and wheel–rail interactions, while properly maintaining track conditions can improve the vehicle performance.
Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms, thereby limiting the generalizability of proposed theories. Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms. The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines. By employing t-distributed stochastic neighbor embedding (t-SNE) for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN, the research redefines the classification of metro rail corrugation based on characteristic information. The analysis encompassed spatial distribution and temporal evolution of this phenomenon. Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%. Notably, ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation. Corrugation primarily manifested in curve sections with radii between 300 and 500 m, featuring ordinary monolithic bed track and steel-spring floating slab track structures, with wavelengths typically between 30 and 120 mm. Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations (40–60 mm), while longer wavelengths (200–300 mm) exhibited distinct fatigue damage characteristics, mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks. A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types. These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.
This paper deals with the problem of recreating horizontal alignments of existing railway lines. The main objective is to propose a simple method for automatically obtaining optimized recreated alignments located as close as possible to an existing one. Based on a previously defined geometric model, two different constrained optimization problems are formulated. The first problem uses only the information provided by a set of points representing the track centerline while the second one also considers additional data about the existing alignment. The proposed methodology consists of a two-stage process in which both problems are solved consecutively using numerical techniques. The main results obtained applying this methodology are presented to show its performance and to prove its practical usefulness: an academic example used to compare with other methods, and a case study of a railway section located in Parga (Spain) in which the geometry of its horizontal alignment is successfully recovered.
The intrusion of obstacles onto railway tracks presents a significant threat to train safety, characterized by sudden and unpredictable occurrences. With China leading the world in high-speed rail mileage, ensuring railway security is paramount. The current laser monitoring technologies suffer from high false alarm rates and unreliable intrusion identification. This study addresses these issues by investigating high-resolution laser monitoring technology for railway obstacles, focusing on key parameters such as monitoring range and resolution. We propose an enhanced non-uniform laser scanning method, developing a laser monitoring system that reduces the obstacle false alarm rate to 2.00%, significantly lower than the 20% standard (TJ/GW135-2015). This rate is the best record for laser monitoring systems on China Railway. Our system operates seamlessly in all weather conditions, providing superior accuracy, resolution, and identification efficiency. It is the only 3D LiDAR system certified by the China State Railway Group Co., Ltd. (Certificate No. [2023] 008). Over three years, our system has been deployed at numerous points along various lines managed by the China State Railway Group, accumulating a dataset of 300,000 observations. This extensive deployment has significantly enhanced railway safety. The development and implementation of our railway laser monitoring system represent a substantial advancement in railway safety technology. Its low false alarm rate (2.00%), high accuracy (20 cm × 20 cm × 20 cm), and robust performance in diverse conditions underscore its potential for widespread adoption, promising to enhance railway safety in China and internationally.
Utilizing the ballast layer with more durable and stable characteristics can help avoid significant expenses due to decreased maintenance efforts. Strengthening the ballast layer with different types of reinforcements or substituting the stone aggregates with the appropriate granular materials could potentially help to achieve this goal by reducing the ballast deterioration. One of the exquisite and most effective solutions to eliminate these challenges is to use waste materials such as steel slag aggregates and useless tires. Utilizing these waste materials in the ballasted railway track will contribute to sustainable development, an eco-friendly system, and green infrastructure. So in a state-of-the-art insightful, the ballast aggregates, including a mixture of steel slag and stone aggregates, are reinforced with a novel kind of geo-grid made of waste tire strips known as geo-scraps. This laboratory research tried to explain the shear strength behavior of the introduced mixing slag-stone ballast reinforced with tire geo-scrap. To achieve this goal, a series of large-scale direct shear tests were performed on the ballast which is reinforced by tire geo-scrap and included various combinations of slag and stone aggregates. The concluded results indicate that the optimal mixing ratio is attained by a combination of 75% slag and 25% stone aggregates which is reinforced by tire geo-scrap at a placing level of 120 mm. In this case, the shear strength, internal friction angle, vertical displacement, and dilatancy angle of stone–slag ballast reinforced with geo-scraps exhibited average changes of + 28%, + 9%, − 28%, and − 15%, respectively.
Understanding the reinforcement effect of the newly developed prestressed reinforcement components (PRCs) (a system composed of prestressed steel bars (PSBs), protective sleeves, lateral pressure plates (LPPs), and anchoring elements) is technically significant for the rational design of prestressed subgrade. A three-dimensional finite element model was established and verified based on a novel static model test and utilized to systematically analyze the influence of prestress levels and reinforcement modes on the reinforcement effect of the subgrade. The results show that the PRCs provide additional confining pressure to the subgrade through the diffusion effect of the prestress, which can therefore effectively improve the service performance of the subgrade. Compared to the unreinforced conventional subgrades, the settlements of prestress-reinforced subgrades are reduced. The settlement attenuation rate (R s) near the LPPs is larger than that at the subgrade center, and increasing the prestress positively contributes to the stability of the subgrade structure. In the multi-row reinforcement mode, the reinforcement effect of PRCs can extend from the reinforced area to the unreinforced area. In addition, as the horizontal distance from the LPPs increases, the additional confining pressure converted by the PSBs and LPPs gradually diminishes when spreading to the core load bearing area of the subgrade, resulting in a decrease in the R s. Under the single-row reinforcement mode, PRCs can be strategically arranged according to the local areas where subgrade defects readily occurred or observed, to obtain the desired reinforcement effect. Moreover, excessive prestress should not be applied near the subgrade shoulder line to avoid the shear failure of the subgrade shoulder. PRCs can be flexibly used for preventing and treating various subgrade defects of newly constructed or existing railway lines, achieving targeted and classified prevention, and effectively improving the bearing performance and deformation resistance of the subgrade. The research results are instructive for further elucidating the prestress reinforcement effect of PRCs on railway subgrades.
During the train meeting events, train equipment compartments are exposed to the worst pressure changes, potentially affecting the ventilation performance of equipment, particularly for electrical facilities equipped with independent air ducts. In this paper, a two-step method is used for numerical computation: (1) obtaining the temporal and spatial transient node data of the flow field sections during the train-passing simulation and (2) using the data as the input data for the equipment compartment simulation. In addition, this paper also compares the difference in equipment ventilation between the single-train and train-passing scenarios in real vehicle tests. The results indicate that the primary factors influencing ventilation effectiveness are the aerodynamic compression and deceleration of airflow induced by the other train’s nose, as well as the instability of the external flow field in the wake of the other train. During train crossing, the air is forced into the air duct, with a maximum ratio of the airflow in-duct to the airflow out-duct reaching 3.2. The average mass flow falls below the rated mass flow for the converter. Compared to the rated air volume of converter, the maximum suppression rates obtained from testing and simulation are – 24.5% and – 16.8%, respectively. Compared to the single-train operation, the maximum suppression rates obtained from testing and simulation are – 15% and – 18%, respectively. These findings provide valuable insights into the design and operation of high-speed trains.