As a key structure in the railway power supply system, the overhead catenary pillar carries the entire weight and dynamic load of the contact suspension device and supporting equipment. Its stability and reliability are directly related to the operational safety and efficiency of electrified railways.

Regarding the phenomenon of abnormal shedding of coating above the support under the cantilever of the catenary pillar in the track running line, a three-dimensional model is established to analyse the rigid cantilever type catenary and the force analysis of the cantilever part is carried out by using ABAQUS to calculate the contact force of the bow network under different running speeds of the high-speed train. The load is applied at the locator end of the simplified model of the cantilever to get the support reaction force at the connection between the cantilever and the support.

The support reaction force is applied as a load to the three-dimensional model of the pillar support; the stress cloud and the stress extreme value of 86.14 MPa are obtained for the pillar and the support part and the fatigue life of the pillar's key parts is calculated to be 12.02 years, respectively.

The upper part of the lower support of the high-speed rail catenary pillar is subjected to the alternating load transmitted by the bow net, which causes the fretting damage at this position, resulting in the abnormal peeling of the coating on the upper part of the lower support. Through combining the ABAQUS analysis with the structural characteristics and operating conditions of the catenary system, the main causes of component failure are determined.

The rapid development of China's railway construction has led to an increase in data generated by the high-speed rail (HSR) catenary system. Traditional management methods struggle with challenges such as poor information sharing, disconnected business applications and insufficient intelligence throughout the lifecycle. This study aims to address these issues by applying building information modeling (BIM) technology to improve lifecycle management efficiency for HSR catenary systems.

Based on the lifecycle management needs of catenary engineering, incorporating the intelligent HSR "Model-Data Driven, Axis-Plane Coordination" philosophy, this paper constructs a BIM-based lifecycle management framework for HSR catenary engineering.

This study investigates the full-process lifecycle management of the catenary system across various stages of design, manufacture, construction and operation, exploring integrated BIM models and data transmission methods, along with key technologies for BIM model transmission, transformation and lightweighting.

This study establishes a lossless information circulation and transmission system for HSR catenary lifecycle management. Multi-stage applications are verified through the construction of the Chongqing-Kunming High-Speed Railway, comprehensive advancing the intelligent promotion and high-quality development of catenary engineering.

With the rapid advancement of China's high-speed rail network, the density of train operations is on the rise. To address the challenge of shortening train tracking intervals while enhancing transportation efficiency, the multi-objective dynamic optimization of the train operation process has emerged as a critical issue.

Train dynamic model is established by analyzing the force of the train in the process of tracing operation. The train tracing operation model is established according to the dynamic mechanical model of the train tracking process, and the dynamic optimization analysis is carried out with comfort, energy saving and punctuality as optimization objectives. To achieve multi-objective dynamic optimization, a novel train tracking operation calculation method is proposed, utilizing the improved grey wolf optimization algorithm (MOGWO). The proposed method is simulated and verified based on the train characteristics and line data of CR400AF electric multiple units.

The simulation results prove that the optimized MOGWO algorithm can be computed quickly during train tracks, the optimum results can be given within 5s and the algorithm can converge effectively in different optimization target directions. The optimized speed profile of the MOGWO algorithm is smoother and more stable and meets the target requirements of energy saving, punctuality and comfort while maximally respecting the speed limit profile.

The MOGWO train tracking interval optimization method enhances the tracking process while ensuring a safe tracking interval. This approach enables the trailing train to operate more comfortably, energy-efficiently and punctually, aligning with passenger needs and industry trends. The method offers valuable insights for optimizing the high-speed train tracking process.

Conventional high-speed railways (HSR) subgrade design methods remain constrained by platform-dependent drafting systems, leading to data interaction hindrances and redundant design processes. This study strives to develop a digital earthwork design methodology that enhances design while reducing collaborative expenses.

A novel digital subgrade design approach, utilizing sophisticated analysis and modeling tools customized for different subgrade elements, is put forward in this study. The methodology incorporates the following essential steps: (1) the advancement of digital analysis and modeling techniques for diverse subgrade components, including surfaces, filling, slopes, retaining structures, and foundation treatments; (2) the formulation of a digital design principle repository incorporating various slope protection combinations; (3) the establishment of a comprehensive digital design framework and process for subgrade cross-sections; and (4) the development and implementation of an open-source digital design system.

The proposed method liberates subgrade design from the constraints of conventional drawing platforms, elevating efficiency, intelligence, and flexibility. The open software architecture and code have achieved over 60% efficiency gains in design workflows during its deployment on three major high-speed rail projects: the Baotou-Yinchuan HSR corridor, Shenyang-Baihe HSR network, and Weifang-Yantai HSR system.

This paper introduces an innovative digital design methodology that enables modular and parametric design for railway subgrade sections. The proposed approach provides a digital base for the intelligent design and maintenance of the next-generation high-speed railway.

Rail corrugation is still one of the unsolved challenges in the railway industry, and the abnormal vibration and high-frequency noise caused by it constitute serious adverse effects on the operating environment. How to control corrugation has been an important research theme, and understanding corrugation evolution features is the necessary prerequisite. This study aims to investigate the specific evolution characteristics of corrugation from the contact stick-slip perspective.

The formation and development processes of corrugation are analyzed by using a self-designed scale-down test device. Specifically, the contact stick-slip characteristics under different creepage conditions are analyzed and the formation mechanism of corrugation is summarized. On the basis of corrugation formation, the trend of corrugation development is further emphasized to completely describe the whole process of corrugation evolution.

The results show that, under the determined vertical load condition, the contact interface appears the creep force-creepage negative slope phenomenon in the transverse direction. The cause of short-pitch corrugation on the rail wheel surface under the smaller angles of attack may be related to the inherent vibration frequency of the test device, and the cause of corrugation on the rail wheel surface under the larger angles of attack is mainly related to the stick-slip vibration induced by contact creep saturation.

This research explores the evolution characteristics of corrugation by adopting a self-designed scale-down test device, and elucidates the mechanism of corrugation in detail.

The indoor vibration compaction test (IVCT) was a key step in controlling the compaction quality for high-speed railway graded aggregate (HRGA), which currently had a research gap on the assessment indicators and compaction parameters.

To address these issues, a novel multi-indicator IVCT method was proposed, including physical indicator dry density (ρ_d) and mechanical indicators dynamic stiffness (K_rb) and bearing capacity coefficient (K₂₀). Then, a series of IVCTs on HRGA under different compaction parameters were conducted with an improved vibration compactor, which could monitor the physical-mechanical indicators in real-time. Finally, the optimal vibration compaction parameters, including the moisture content (ω), the diameter-to-maximum particle size ratio (R_d), the thickness-to-maximum particle size ratio (R_h), the vibration frequency (f), the vibration mass (M_c) and the eccentric distance (r_e), were determined based on the evolution characteristics for the physical-mechanical indicators during compaction.

All results indicated that the ρ_d gradually increased and then stabilized, and the K_rb initially increased and then decreased. Moreover, the inflection time of the K_rb was present as the optimal compaction time (T_lp) during compaction. Additionally, optimal compaction was achieved when ω was the water-holding content after mud pumping, R_d was 3.4, R_h was 3.5, f was the resonance frequency, and the ratio between the excitation force and the M_c was 1.8.

The findings of this paper were significant for the quality control of HRGA compaction.

Salt rock from salt lakes can serve as a cost-effective material for subgrade filling, as demonstrated in projects like the Qarhan Salt Lake section of the Qinghai-Tibet Railway and the Qarhan Salt Lake section of the G215 Highway. This state-of-the-art paper aims to summarize the engineering properties of salt rock filling and present the advances of its utilization.

This paper collects and analyzes laboratory and field data of salt rock filling from previous studies to present a comprehensive analysis of the engineering properties and utilization of salt rock fillings.

Salt rock primarily contains minerals such as halite and glauberite, which contribute to its unique phase-changing behavior under varying environmental conditions, impacting its mechanical properties. Salt rock filling shrinks when in contact with vapor or unsaturated brine and expands under cooling or evaporation. Its use is particularly recommended for arid regions, with specific restrictions depending on the structure type. This paper discusses suggested countermeasures to mitigate these issues, as well as key quality acceptance indices for salt rock filling compaction. Moisture content after air-drying is recommended as a crucial parameter for construction quality control.

This review aims to support future research and engineering practices in salt rock subgrade applications.

The study aims to build a high-precision longitudinal dynamics model for heavy-haul trains and validate it with line test data, present an optimization method for multi-stage cyclic brakes based on the model and conduct a multi-objective detailed evaluation of the driver's manipulation during cyclic braking.

The high-precision longitudinal train dynamics model was established and verified by the cyclic braking test data of the 20,000 t heavy-haul combination train on the long and steep downgrade. Then the genetic algorithm is employed for optimization subsequent to decoupling multiple cyclic braking procedures, with due consideration of driver operation rules. For evaluation, key manipulation assessments in the scenario are prioritized, supplemented by multi-objective evaluation requirements, and the computational model is employed for detailed evaluation analysis.

Based on the model, experimental data reveal that the probability of longitudinal force error being less than 64.6 kN is approximately 68%, 95% for less than 129.2 kN and 99.7% for less than 193.8 kN. Upon optimizing manipulations during the cyclic braking, the maximum reduction in coupler force spans from 21% ~23.9%. And the evaluation scores imply that a proper elevation of the releasing speed favors safety. A high electric braking force, although beneficial to some extent for energy-saving, is detrimental to reducing coupler force.

The results will provide a theoretical basis and practical guidance for further ensuring the safety and energy-efficient operation of heavy haul trains on long downhill sections and improving the operational quality of heavy-haul trains.

The paper aims to clarify the operation rationality of high speed trains (HSTs) under tunnel condition with the speed of 400 km/h through representative aerodynamic factors including running drag, eardrum comfort, carriages noise, aerodynamic loads on tunnel ancillary facilities and HST, micro-pressure waves, and then put forward engineering suggestions for higher speed tunnel operation based on the analysis.

Based on the field measurement data of CR400AF-C and CR400BF-J tunnel operation, correlations between each aerodynamic indicators with HST speed were established. By analyzing the safety reserve of aerodynamic indicators at 350 km/h and the sensitivity of each indicator to HST speed increasing and the indicators' formation mechanism, the coupling relationship between various indicators was obtained.

The sensitivity of different aerodynamic indicators to speed variation differed. The aerodynamic indicators representing flow field around HST showed a linear relationship with HST speed including noise, eardrum comfort, aerodynamic load on HST body. The positive aerodynamic load on tunnel auxiliary facilities and the micro-pressure wave at the entrance of the tunnel have the same sensitivity to the 3th-power relation of HST speed. The over-limit proportion of micro-pressure wave was the highest among the indicators, and aerodynamic buffering measures were recommended for optimization. The open tunnel pressure relief structure is recommended, while allowing trains to pass through the tunnel at an unconditional speed of 380 km/h.

Comprehensive evaluation of multiple aerodynamic indicators for HST tunnel operation with higher speeds was realized. The main engineering requirements to release aerodynamic effect were identified and the optimization scheme is proposed.

MxV Rail conducted multiple single tie push tests (STPTs) between 2020 and 2023 to assess the changes in lateral tie resistance from tonnage accumulation, dynamic track stabilizers (DTS), tie type and ballast condition. High lateral tie resistance is necessary for preventing lateral misalignments and track buckles. Therefore, understanding how various factors affect the lateral tie resistance will aid in the development of track buckling risk assessments and ballast maintenance best practices.

The test involved tamping a section of track that consisted of both concrete and wood ties and then increasing the lateral tie resistance, using either tonnage during speed restrictions or a DTS. The STPTs and top-of-rail (TOR) elevation measurements were taken at multiple stages, including immediately after tamping and then after different tonnage increments or DTS. The results from this test were then added to a compiled measurement from previous tests, and the results from all the tests were used to develop general guidelines for ballast maintenance best practices and trade-off considerations.

The results showed multiple factors affect the lateral track strength and therefore the susceptibility to misalignments and track buckles. The disturbance from ballast tamping can reduce the lateral track strength by 20-80% (~45% median) and can be compacted from either tonnage (25-50% regain in strength after 0.1 m gross ton or MGT) or DTS (33-78% regain in strength). The amount of ballast (shoulder width and crib height), tie type and ballast characteristics all have a meaningful role in lateral track strength.

This paper is based on the testing programs conducted by authors at MxV Rail.