Traction power systems (TPSs) play a vital role in the operation of electrified railways. The transformation of conventional railway TPSs to novel structures is not only a trend to promote the development of electrified railways toward high-efficiency and resilience but also an inevitable requirement to achieve carbon neutrality target. On the basis of sorting out the power supply structures of conventional AC and DC modes, this paper first reviews the characteristics of the existing TPSs, such as weak power supply flexibility and low-energy efficiency. Furthermore, the power supply structures of various TPSs for future electrified railways are described in detail, which satisfy longer distance, low-carbon, high-efficiency, high-reliability and high-quality power supply requirements. Meanwhile, the application prospects of different traction modes are discussed from both technical and economic aspects. Eventually, this paper introduces the research progress of mixed-system electrified railways and traction power supply technologies without catenary system, speculates on the future development trends and challenges of TPSs and predicts that TPSs will be based on the continuous power supply mode, employing power electronic equipment and intelligent information technology to construct a railway comprehensive energy system with renewable energy.
Dynamic wheel–rail contact forces induced by a severe form of wheel tread damage have been measured by a wheel impact load detector during full-scale field tests at different vehicle speeds. Based on laser scanning, the measured three-dimensional damage geometry is employed in simulations of dynamic vehicle–track interaction to calibrate and verify a simulation model. The relation between the magnitude of the impact load and various operational parameters, such as vehicle speed, lateral position of wheel–rail contact, track stiffness and position of impact within a sleeper bay, is investigated. The calibrated model is later employed in simulations featuring other forms of tread damage; their effects on impact load and subsequent fatigue impact on bearings, wheel webs and subsurface initiated rolling contact fatigue of the wheel tread are assessed. The results quantify the effects of wheel tread defects and are valuable in a shift towards condition-based maintenance of running gear, and for general assessment of the severity of different types of railway wheel tread damage.
Concrete slabs are widely used in modern railways to increase the inherent resilient quality of the tracks, provide safe and smooth rides, and reduce the maintenance frequency. In this paper, the elastic performance of a novel slab trackform for high-speed railways is investigated using three-dimensional finite element modelling in Abaqus. It is then compared to the performance of a ballasted track. First, slab and ballasted track models are developed to replicate the full-scale testing of track sections. Once the models are calibrated with the experimental results, the novel slab model is developed and compared against the calibrated slab track results. The slab and ballasted track models are then extended to create linear dynamic models, considering the track geodynamics, and simulating train passages at various speeds, for which the Ledsgård documented case was used to validate the models. Trains travelling at low and high speeds are analysed to investigate the track deflections and the wave propagation in the soil, considering the issues associated with critical speeds. Various train loading methods are discussed, and the most practical approach is retained and described. Moreover, correlations are made between the geotechnical parameters of modern high-speed rail and conventional standards. It is found that considering the same ground condition, the slab track deflections are considerably smaller than those of the ballasted track at high speeds, while they show similar behaviour at low speeds.
Railway accidents, particularly serious derailments, can lead to catastrophic consequences. Therefore, it is essential to prevent derailment escalation to reduce the likelihood of severe derailments. Train post-derailment behaviours and containment methods play a critical role in preventing derailment escalation and providing passive safety protection and accident prevention in the event of a derailment. However, despite the increasing attention on this field from academia and industry in recent years, there is a lack of systematic exploration and summarization of emerging applications and containment methods in train post-derailment research. For this reason, this paper presents a comprehensive review of existing studies on train post-derailment behaviours, encompassing various topics such as post-derailment contact–impact models, dynamic modelling and simulation techniques, and the primary factors influencing post-derailment behaviours. Significantly, this review introduces and elucidates substitute guidance mechanisms (SGMs), which serve as railway-specific passive safety protection and accident prevention measures. The various types of SGMs are depicted, and their ongoing developments and applications are explored in depth. The review additionally points out several unresolved challenges including the adverse effects of SGMs, and proposes future research directions to advance the theoretical understanding and practical application of train post-derailment behaviours and containment methods. This review seeks to be a valuable reference for railway industry professionals in preventing catastrophic derailment consequences through post-derailment containment methods.
Appropriate interaction between pantograph and catenary is imperative for smooth operation of electric trains. Changing heights of overhead lines to accommodate level crossings, overbridges, and tunnels pose significant challenges in maintaining consistent current collection performance as the pantograph aerodynamic profile, and thus aerodynamic load changes significantly with operational height. This research aims to analyse the global flow characteristics and aerodynamic forces acting on individual components of an HSX pantograph operating in different configurations and orientations, such that the results can be combined with multibody simulations to obtain accurate dynamic insight into contact forces. Specifically, computational fluid dynamics simulations are used to investigate the pantograph component loads in a representative setting, such as that of the recessed cavity on a Class 800 train. From an aerodynamic perspective, this study indicates that the total drag force acting on non-fixed components of the pantograph is larger for the knuckle-leading orientation rather than the knuckle-trailing, although the difference between the two is found to reduce with increasing pantograph extension. Combining the aerodynamic loads acting on individual components with multibody tools allows for realistic dynamic insight into the pantograph behaviour. The results obtained show how considering aerodynamic forces enhance the realism of the models, leading to behaviour of the pantograph–catenary contact forces closely matching that seen in experimental tests.
The high and steep slopes along a high-speed railway in the mountainous area of Southwest China are mostly composed of loose accumulations of debris with large internal pores and poor stability, which can easily induce adverse geological disasters under rainfall conditions. To ensure the smooth construction of the high-speed railway and the subsequent safe operation, it is necessary to master the stability evolution process of the loose accumulation slope under rainfall. This article simulates rainfall using the finite element analysis software’s hydromechanical coupling module. The slope stability under various rainfall situations is calculated and analysed based on the strength reduction method. To validate the simulation results, a field monitoring system is established to study the deformation characteristics of the slope under rainfall. The results show that rainfall duration is the key factor affecting slope stability. Given a constant amount of rainfall, the stability of the slope decreases with increasing duration of rainfall. Moreover, when the amount and duration of rainfall are constant, continuous rainfall has a greater impact on slope stability than intermittent rainfall. The setting of the field retaining structures has a significant role in improving slope stability. The field monitoring data show that the slope is in the initial deformation stage and has good stability, which verifies the rationality of the numerical simulation method. The research results can provide some references for understanding the influence of rainfall on the stability of loose accumulation slopes along high-speed railways and establishing a monitoring system.
The meso-dynamical behaviour of a high-speed rail ballast bed with under sleeper pads (USPs) was studied. The geometrically irregular refined discrete element model of the ballast particles was constructed using 3D scanning techniques, and the 3D dynamic model of the rail–sleeper–ballast bed was constructed using the coupled discrete element method–multi-flexible-body dynamics (DEM–MFBD) approach. We analyse the meso-mechanical dynamics of the ballast bed with USPs under dynamic load on a train and verify the correctness of the model in laboratory tests. It is shown that the deformation of the USPs increases the contact area between the sleeper and the ballast particles, and subsequently the number of contacts between them. As the depth of the granular ballast bed increases, the contact area becomes larger, and the contact force between the ballast particles gradually decreases. Under the action of the elastic USPs, the contact forces between ballast particles are reduced and the overall vibration level of the ballast bed can be reduced. The settlement of the granular ballast bed occurs mainly at the shallow position of the sleeper bottom, and the installation of the elastic USPs can be effective in reducing the stress on the ballast particles and the settlement of the ballast bed.