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Implicit Forward Design Method for Linear Engineering Geological Sections

DAI Junhao

Journal of Railway Engineering Society. 2025, 42(12): 1-6.

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Research purposes: The geological phenomena faced by long linear projects such as rail transit, highways, oil and gas pipelines, and transmission lines are characterized by significant variations and strong anisotropy, leading to heavy workload, low mapping efficiency, sparse data sources, and high subjectivity in conventional geological cross-section design. To address these issues and enhance the efficiency and accuracy of geological section design for linear engineering, this study proposes an implicit modeling-driven forward design method for geological sections in such projects.
Research conclusions: (1) An implicit geological modeling-based forward design method for geological sections of linear engineering is proposed. (2) Using geological borehole stratification data, topographic data, and geological plans as multi-source data inputs, the method performs data preprocessing, implicit geological modeling, free-form model slicing, and forward section design. (3) In the application to the Mafu River Grand Bridge project of a railway line, the model and sections effectively characterized the distribution of complex geological bodies at the bridge site. (4) Compared with traditional manual geological mapping methods, the proposed approach increases design efficiency by approximately 75% while satisfying the requirements of downstream design disciplines.(5) The results can be widely applied in geological investigation and design for various types of linear engineering.

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A Calculation Method for Concrete Crack Width Based on OFDR Optical Fiber Technology

WU Dongliang

Journal of Railway Engineering Society. 2025, 42(12): 7-11.

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Research purposes: The location and width characteristics of cracks are important parameters for evaluating the safety status of reinforced concrete structures. To this end, based on the underground continuous wall-waist beam-support node test of a prefabricated subway station, an innovative method for calculating the crack width of reinforced concrete components using optical frequency domain reflectometer (OFDR) distributed optical fiber technology was proposed. This approach involves monitoring crack location and steel bar strain through OFDR technology, combined with existing crack width calculation methods.
Research conclusions: (1) The steel bar strain measured based on OFDR distributed optical fiber technology accurately identified the cracking location of reinforced concrete, and the magnitude was slightly higher than the calculated value in the specification and the strain gauge test value, demonstrating good testing performance. (2) The crack width calculated from the strain of steel bars measured by OFDR distributed optical fiber technology differs from the directly measured crack width to some extent, but the variation patterns captured by both methods are basically consistent. (3) A calculation method for crack width in concrete structures based on OFDR distributed optical fiber technology has been proposed. Compared with the recommended formula in the code, only a comprehensive correction factor c is introduced, and the recommended value of c is 0.73. (4) This study can provide important references for the location and width calculation of crack in concrete.

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Study on the Failure Modes of Staged Excavation in a Two-layered Soil Foundation Pit with Soft Upper and Hard Lower Layers

WAN Peng

Journal of Railway Engineering Society. 2025, 42(12): 12-17.

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Research purposes: To investigate failure modes during staged excavation of foundation pits in upper-soft and lower-hard strata, this study focused on a large-scale foundation pit project in Fuyang, Hangzhou, characterized by dual geological conditions. Numerical simulations were conducted to analyze potential failure patterns. The effects of key parameters including width-to-depth ratio of inner pits, modulus ratio between soft and hard layers, and insertion ratio of diaphragm walls were investigated.
Research conclusions: (1) The research results indicate four basic failure modes: toe-kick failure of exterior walls, basal heave failure of exterior walls, structural fracture failure of exterior walls, and toe-kick failure of interior walls. (2) With the increase of inner pit width-to-depth ratio, the failure mode transitions from sliding failure to shear failure at exterior walls, where the mid-section of supporting structures bears larger active earth pressure, and the stability of the foundation pit is governed by the stiffness of the exterior walls. (3) The modulus ratio between soft and hard layers shows limited influence on the development of the potential failure surfaces and the stability of the foundation pit. The existence of hard layers alters the location of maximum lateral displacement in diaphragm walls, with peak deformation occurring near 0.8 times the excavation depth. (4) Special attention should be paid to fracture risks when diaphragm walls penetrate stiff layers, as excessive deformation in shallow soft layers may induce structural failure. (5) This research achievement can provide certain references for the design and construction of ultra-large and ultra-deep foundation pit projects under similar overlying soft and underlying hard stratum conditions.

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Study on the Rock Damage Constitutive Model Considering Microcrack Interaction

JIA Zheqiang, ZHANG Ru, WANG Dong, REN Li, XU Zhengxuan, XIE Jing, WANG Zhewei, XIAO Kun

Journal of Railway Engineering Society. 2025, 42(12): 18-23.

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Research purposes: Due to the complex structural characteristics of deep rock masses, the deformation and failure behavior of surrounding rock in deep-buried tunnels is significantly uncertain. Traditional microcrack models often ignore the interaction between cracks. This paper takes the mechanism of microcrack propagation and damage as the starting point, and introduces a self-consistent model based on the traditional microcrack model, aiming to more accurately describe the rock mechanical behavior under complex geological conditions.
Research conclusions: (1) Based on microscopic damage mechanics, this paper fully considers the initiation, propagation, and interaction mechanisms of sliding crack models, and constructs a rock microcrack damage constitutive model that accounts for crack interactions. The feasibility of the model is verified by comparing it with experimental data. (2) The constitutive relationship of the microcrack model under different confining pressures, primary microcrack lengths and densities, and fracture toughness is systematically analyzed, and the applicability of the model under different conditions is verified. (3) The research results can provide theoretical support for the refined analysis and evaluation of the deformation and failure of surrounding rock masses in deep-buried tunnels, and are applicable to the field of engineering geological investigation.

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Key Technology of High Polymer Grouting Lifting for Subgrade Settlement of High Speed Railway in Operation

ZHOU Yong

Journal of Railway Engineering Society. 2025, 42(12): 24-29.

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Research purposes: Due to long-term dynamic train loads and complex service environments, some ballastless track subgrades have experienced uneven settlement beyond the adjustable range of the fastener system, which seriously affects the train operational safety. Through numerical simulation and orthogonal test, the key control parameters and construction process parameters of high polymer grouting lifting are studied, and the dynamic characteristics of track structure before and after grouting lifting are compared and analyzed, providing theoretical guidance for subsequent engineering practice.
Research conclusions: (1) Under the condition of ensuring the normal use function of the track structure, considering the construction efficiency and lifting accuracy of high polymer grouting, the maximum lifting amount per time can be 10 to 15 mm, and the optimal lifting hole spacing should be 5.2 m, and multiple cyclic lifting can be performed within a single track possession. (2) By using a larger grouting pressure of 7 to 9 MPa and a shorter reaction time of 5 to 8 s, and timely adjusting the injection stop rhythm during the early, mid and late stages of the grouting lifting process, it’s possible to achieve the best lifting effect with minimum construction cost. (3) After the high polymer grouting lifting, the formed cementation layer can be well matched with the track-subgrade system, and the dynamic characteristics of each track layer do not change much, and are far below the code-specified limits. (4) The results of this study can further improve the operation and maintenance technology system of high speed railway, which is of great significance to ensure the safe operation of high speed railway.

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Study on the Influence of Long-span Steel Truss Bridge Pier Settlement on Line Regularity

YANG Wenmao, LIN Hongsong, XU Hao

Journal of Railway Engineering Society. 2025, 42(12): 30-35.

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Research purposes: Padma Bridge Railway Link in Bangladesh is a mixed passenger and freight railway with a design speed of 120 km/h for passenger cars and 80 km/h for freight cars, in which the Padma Multipurpose Bridge adopts a 900 m long continuous steel truss bridge for its main bridge. The theoretical maximum settlement of the bridge pier is 80 mm, far exceeding the limit value in current code of China. The vertical deformation of track caused by pier settlement reduces the line regularity and adversely affects the vehicle running stability. Therefore, it is urgent to quantitatively assess the track regularity and vehicle dynamic characteristics under different settlement conditions to ensure driving safety.
Research conclusions: (1) When the settlement of a single pier reaches 80 mm within the span of a steel truss girder, the maximum deviation in track longitudinal level is 0.685 mm, which is far less than the code limit value, indicating that the line regularity is in good condition. (2) When settlement of the pier at the junction of adjacent steel truss girders reaches 80 mm, the maximum deviation in track longitudinal level is 3.360 mm, which is still less than the code limit value. Meanwhile, to further improve the capacity to maintain line regularity, adjustable bearings are adopted in the bridge to conveniently adjust elevation of the beam ends after the pier settlement. (3) When passenger and freight cars pass through the settlement section at speeds of 120 km/h and 80 km/h, respectively, all critical dynamic indices, such as derailment coefficient, wheel unloading rate, wheelset lateral force and car body vibration acceleration, demonstrate compliance with the code requirements. (4) This study can provide reference for the settlement impact assessment of long-span continuous steel truss bridge piers.

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Study on the Influence of Fastener Stiffness in Subway Rapid Transit on Uneven Rail Wear

WANG Weihua, WEI Zhen, SHEN Yizhe

Journal of Railway Engineering Society. 2025, 42(12): 36-40.

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Research purposes: As a common disease in the field of rail transit, rail corrugation not only causes train vibration and noise, but also accelerates the fatigue damage of the fastening system, leading to the occurrence of spring bar fracture and threatening train safety. To investigate the influence of the fastener stiffness in subway rapid rail on the frequency-domain response of uneven rail wear, this paper established a three-dimensional vehicle-track coupled dynamics model incorporating USFD rail wear. The vertical wheel-rail forces and the frequency-domain response of rail uneven wear under varying fastening stiffness and harmonic roughness excitation frequencies were analyzed.
Research conclusions: (1) Both vertical wheel-rail forces and rail wear depth exhibit an upward fluctuation trend under 200~1 000 Hz harmonic excitation, peaking at the local second-order (350~420 Hz) and third-order (650~710 Hz) resonant frequencies of the rail between bogie wheelsets. (2) As fastening stiffness increases, the characteristic frequencies of these peaks shift toward higher frequencies, while the corresponding rail uneven wear depth initially increases and then decreases. (3) When fastening stiffness falls within the range of 10~25 kN/mm, significantly deeper rail uneven wear occurs.（4）These conclusions provide theoretical guidance for fastening stiffness design and operational maintenance.

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Technological Innovation and Application of Mountain Cog Tourism Rail Transit

YU Haowei, KOU Junyu, YANG Yang, WANG Kaiyun

Journal of Railway Engineering Society. 2025, 42(12): 41-45.

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Research purposes: The national “dual carbon” strategy is promoting the green and low-carbon transformation and upgrading of rail transit. The traditional rail transit systems are difficult to fully meet the diversified and personalized needs of tourism traffic.The cog railway with excellent climbing ability and terrain adaptability provides an innovative solution for mountain tourism transportation. This paper takes the mountain cog railway with “wheel rail + cog rail” dual-system design as the research object, and discusses the technological innovation and application of mountain tourism rail transit.
Research conclusions: (1) In response to the needs of practical application scenarios of mountain cog railway, China has achieved a series of innovative achievements in multiple fields, including vehicle engineering technologies, such as lightweight and compact design, cog drive technology, and cog bogie for 120‰ gradient, as well as rack rail structure and turnout system, rack transition device and signal control technology, infrastructure stability. (2) In the future, the cog railway will continue to tackle key problems in the aspects of cog bogie for 250‰ gradient, collaborative vehicle-rail design optimization, extreme environmental adaptability, the establishment of standard systems, and specialized construction technique. (3) The findings of this study can provide reference and guidance for the technical research and development of mountain cog tourism rail transit projects.

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Research on Active Control Design of Flying-swallow-style Self-balancing Arch Bridges for High-speed Railways

WEI Chengfeng, AI Zongliang, LIU Wei, XIANG Lvkai, CAI Chao, PENG Fubing

Journal of Railway Engineering Society. 2025, 42(12): 46-51.

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Research purposes: To address the issues of uneven stress distribution at arch footings and significant bearing reaction differences in flying-swallow-style self-balancing arch bridges for high-speed railways, this study investigates an active control design technique of "shortening tie-beam fabrication length".Using the (72+320+72) m flying-swallow-style self-balancing arch bridge of Jianyang Tuojiang River Super Major Bridge on Chengdu-Chongqing Middle Line High-Speed Railway as a case study, the research employs finite element analysis and optimization theory to develop this innovative approach.
Research conclusions: (1) The active control technology has demonstrated remarkable effectiveness in optimizing the mechanical behavior of the flying-swallow-style self-balancing arch bridge, achieving significant performance enhancements during operation: concrete stress at side arch abutments was reduced by 62.2%, steel tube stress at main arch abutments decreased by 25.1%, the differential reaction force between double-row bearings was diminished by 86.4%, and displacement at movable bearings was reduced by 54.7%. (2) Through the application of optimization theory, the study successfully determined the optimal reduction value for tie-beam fabrication length by systematically evaluating multiple performance indicators, including structural internal forces, reaction force differentials, and bearing displacements, thereby significantly improving computational efficiency. (3) The implementation of this active control technology was accomplished through the strategic application of proactive tensioning at pre-designed closure joints in the tie-beams, achieving precise structural alignment with a maximum applied tension force reaching approximately 5 800 metric tons. (4) The comprehensive research outcomes presented in this study provide a valuable technical reference and practical guidance for future design and implementation of active control technologies in high-speed railway flying-swallow-style self-balancing arch bridge projects.

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Theoretical Research on Deformation Grouting Control for High-speed Railway Bridges Adjacent to Soft Soil Foundation Pits

MENG Changjiang, SUN Honglin, ZHANG Xiaoling, ZHANG Bingjie, TU Qizhu

Journal of Railway Engineering Society. 2025, 42(12): 52-58.

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Research purposes: In response to the difficulty of controlling 2~3 mm deformation of high-speed railway bridges in close proximity to soft soil deep foundation pits, existing passive control measures, including strengthening retaining structures, zoning excavation, and setting isolation piles, are difficult to control and can significantly increase costs and project duration. This article is based on a deep foundation pit project adjacent to a high-speed railway bridge in the Pearl River Delta region. It conducts a theoretical analysis of active grouting deformation, establishes a mechanical analysis model, and compares the on-site grouting test results with the theoretical results. The displacement variation laws of the foundation soil and bridge pier pile foundation under different influencing factors are explored.
Research conclusions: (1) The mechanical analysis model established by combining the theory of ball hole expansion under the action of grouting and the Winkler foundation beam model with existing soil displacement can better simulate the deformation of high-speed railway bridges adjacent to soft soil deep foundation pits under grouting. (2) The horizontal displacement of the soil caused by grouting exhibits an outward convex pattern along the depth direction, with the maximum horizontal displacement located at the top of the grouting depth range. As the grouting distance increases, the displacement of the soil at the same burial depth rapidly decreases. (3) The presence of pore water pressure can affect the consistency of the slurry, thereby weakening the effectiveness of active grouting deformation control technology. (4) The results of this study can provide theoretical and engineering references for deformation control of high-speed railway bridges in close proximity to soft soil deep foundation pits.

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An Intelligent Method for Classifying Tunnel Surrounding Rock Grades Using Magnetotelluric Sounding

XU Guangchun

Journal of Railway Engineering Society. 2025, 42(12): 59-64.

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Research purposes: The classification of tunnel surrounding rock grades is a critical component in tunnel investigation and design, serving as a key basis for selecting construction methods and reinforcement measures. Traditional classification methods, which primarily rely on lithology, often yield significant errors. Magnetotelluric (MT) sounding, known for its great depth penetration and high resolution, can obtain resistivity distribution at significant depths, offering a new technical approach for identifying the surrounding rock grades of deep-buried tunnels. However, the interpretation of MT sounding results heavily depends on expert experience, making it difficult to use directly for accurate classification. This study aims to establish a correlation between MT resistivity and surrounding rock grades by leveraging large model analysis technology, taking into account influencing factors such as lithology, weathering, fracture development, and groundwater enrichment.
Research conclusions: This paper selects magnetotelluric sounding data from 67 tunnels, totaling 514 304 meters in length, to develop an intelligent discrimination model for surrounding rock grades that integrates resistivity, lithology, and water content. A quantitative identification method was established, leading to the following conclusions: (1) The proposed method fully utilizes the advantages of magnetotelluric exploration technology in deep geological structure exploration, improving the accuracy of surrounding rock grade classification for tunnels. (2) By employing a data-driven intelligent analysis on a substantial set of field measurements, the developed intelligent model achieved an accuracy rate of 96.54%, which is markedly superior to traditional methods. (3) The findings of this research hold significant value for optimizing tunnel construction plans and reducing project costs.

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Rockburst Risk Assessment of High Geo-stress Tunnel in Yarlung Zangbo River Suture Zone

ZHOU Hang, ZHAO Xiaoyan, FENG Tao, ZHANG Min, CHEN Shikuo, YUAN Dong

Journal of Railway Engineering Society. 2025, 42(12): 65-70.

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Research purposes: The deep-buried tunnel in the Yarlung Zangbo River Suture Zone is located in the hinterland of the Qinghai-Tibet Plateau. The region has a complex geological structural background and strong tectonic activity, resulting in an exceptionally high initial in-situ stress state in the engineering area. Hard rock rockburst is the core risk affecting the construction and operational safety. Based on borehole in-situ stress measurements and inversion analysis of the initial stress field, this study investigates the high in-situ stress characteristics of the deep-buried long tunnel in the Yarlung Zangbo Suture Zone and assesses the rockburst risk.
Research conclusions: (1) The deep-buried tunnel in the Yarlung Zangbo River suture zone is subjected to significant in-situ stress challenges. The maximum horizontal principal stress S_H and the vertical principal stress S_v of the tunnel axis ranged from 3.3 to 43.6 MPa and 0.6 to 48.4 MPa, respectively. A total of 7 000 m (accounting for 60.3%) of the tunnel length is located in high to extremely high in-situ stress zones, and the high stress environment is the key dynamic factor inducing rockburst disasters. (2) The deep-buried tunnel in the Yarlung Zangbo River suture zone is controlled by both horizontal tectonic stress and self-weight stress, showing a significant depth effect. When the buried depth of the tunnel is less than 1 300 m, the horizontal tectonic stress is dominant. When the buried depth of the tunnel exceeds 1 300 m, the vertical principal stress of the large buried depth begins to dominate. (3) The strata along the deep-buried tunnel in the Yarlung Zangbo Suture Zone mainly consist of Class Ⅱ and Ⅲ hard brittle surrounding rock. The rock mass integrity coefficient generally ranges from 0.60 to 0.85. Based on rockburst tendency tests using the elastic energy index (W_et) and the brittleness coefficient B (R_c/R_t), the diorite and gneiss exhibit the energy storage and release conditions indicative of a moderate rockburst tendency. (4) Based on the double-index evaluation method for tunnel rockburst,the full length of the deep-buried tunnel in the Yarlung Zangbo River Suture Zone is 11 600 m, and the total length of potential rockburst hazard zones is 8 500 m, accounting for 73.3% of the tunnel.Among these, the intense rockburst risk section spans 2 000 m, accounting for 23.5% of the total rockburst-prone sections. (5) The high in-situ stress characteristics in the survey area of the deep-buried tunnel are extremely prominent.The magnitude and direction of in-situ stress change frequently in local sections,showing notable time-dependent effects and a prolonged secondary stress adjustment period.Additionally, the well-developed structural planes in the diorite and gneiss within the tunnel engineering area may lead to ultra-long time-delayed rockburst in sections DK17+750~DK18+250 and DK19+000~DK21+000.(6) The research findings can provide a reference for route selection, rockburst risk assessment, prevention and control of similar deep-buried long tunnels.

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Research on Measures to Reduce Rail Potential on Single-line Electrified Railways

LIU Ruofei

Journal of Railway Engineering Society. 2025, 42(12): 71-76.

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Research purposes: In the absence of an integrated grounding system and the infeasibility of lateral connections between up and down track rails, certain single-track electrified railways in high soil resistivity areas face elevated rail potential issues.This is attributed to two main factors:first, the traction current of high-power locomotives is substantially increased; second, the rail-to-earth leakage resistance is high due to the high soil resistivity.The combined influence of these factors leads to higher rail potentials compared to other lines, which in severe cases may endanger personnel and equipment safety, disrupt normal railway operations, and thus require targeted mitigation measures.
Research conclusions: (1) There is currently a lack of clearly defined standards or specifications regarding rail potential limits for single-track electrified railways. Given the distinctive features of such railways, strict adherence to high-speed railway acceptance codes under present conditions remains questionable. (2) For reducing rail potential in single-track electrified railways, the combined solution of adding grounding electrodes and installing a continuous ground wire has been demonstrated as effective. (3) In addressing elevated rail potential, it is advisable to perform systematic simulation calculations that integrate track conditions, load magnitude, soil resistivity, and other relevant factors in order to identify economical and efficient engineering solutions and avoid unnecessary investment. (4) This study offers valuable references and insights for managing rail potential in single-track electrified railways located in high soil resistivity regions.

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Research on Train-induced Wind Vibration of Catenary Additional Conductors

LUO Jian, WU Mengzhen, GU Xiaodong, HE Changhong, ZHANG Qi, HAN Lingqing, LIU Jidong

Journal of Railway Engineering Society. 2025, 42(12): 77-83.

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Research purposes: As an important component of the non-redundant catenary system, the catenary additional conductor is affected by complex train-induced wind loads when high-speed trains pass by, resulting in significant vibrations. This may further induce accidents such as wire and strand fractures of the catenary additional conductor, posing major hazards to the safe and stable operation of high-speed railways. It is urgent to conduct systematic research on the train-induced wind vibration of catenary additional conductors and propose schemes to enhance their wind resistance.
Research conclusions: (1) In the canopy station scenario, the amplitude of train-induced wind vibration of the protective wire (PW) is significantly higher than that in other scenarios, resulting in a prominent risk of wire and strand fractures. In contrast, the auto-transformer feeder (AT) exhibits a notably lower vibration amplitude due to its greater distance from the train. (2) Under the extreme condition where the vertical displacement amplitude of the PW reaches 250 mm under train-induced wind loads, the maximum stress at its ends exceeds the tensile strength of the outer hard aluminum wire, directly leading to the breakage of the hard aluminum wire. (3) This paper aims to reduce the maximum stress at the ends of the PW during train-induced wind vibration, with the constraint that its safety factor for the maximum breaking force being greater than 2.5 within the full service temperature range. A joint optimization of the tension settings and clamp types of the PW is performed. After optimization, the maximum stress at the ends of the PW decreases significantly, and its safety and reliability are improved. (4) The findings of this research are applicable to the professional field of catenary systems in electrified railways.

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Hierarchical Component-driven Modeling of Section Models for Railway Yards with Dense Topology

DING Lening

Journal of Railway Engineering Society. 2025, 42(12): 84-89.

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Research purposes: The cross-sectional design of railway yards involves numerous disciplines and complex equipment. It is fundamentally characterized by intricate interrelations, coupling constraints, and high-density adjacency topology across macro to micro levels.A key challenge in current design practice is how to accurately characterize these features and maintain model consistency throughout the dynamic, interactive design process. Research on cross-sectional design based on ontological modeling and the digital twin concept helps to comprehensively describe its information structure and clarify the implicit, complex coupling constraints and topological relationships. To address this, this paper proposes a hierarchical component-based ontological modeling method for cross-sections and demonstrates its application in the case of Qingyang Station on the Pingliang-Qingyang Railway.
Research conclusions: (1) To address the characteristics of "complex equipment and intricate relationships" in cross-sectional design, this paper proposes a hierarchical component-based method for constructing the cross-sectional ontology model. The concepts involved in the design are categorized from macro to micro into yard-level, subgrade body-level, filling zone-level, and filling layer-level components. Based on this, the core modeling primitives of the ontology—classes (or concepts) and relationships—are abstracted. (2) OWL was employed to accurately characterize the ontological classes and their interrelationships for the railway yard cross-section.(3) An ontological model for the cross-section of Qingyang Station was constructed using the Protégé software.(4) The research findings pave the way for further exploration into the deep integration of this ontological model with BIM and GIS platforms, as well as the development of an automated design conflict detection and optimization feedback mechanism using rule-based reasoning. This will promote the transition of railway yard digital design towards greater intelligence and automation.

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Deformation Monitoring Using a Posteriori-residual-based Adaptive Satellite Selection Algorithm

ZHU Tieshuan

Journal of Railway Engineering Society. 2025, 42(12): 90-94.

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Research purposes: To address the challenges of satellite selection and unstable positioning in GNSS deformation monitoring under complex environments, this study proposes a posteriori-residual-based adaptive satellite selection method for single-BDS monitoring. A multi-system double-difference carrier phase filtering workflow is developed, incorporating cycle-slip detection, clock jump correction, state parameter estimation, and ambiguity fixing. A posteriori-residual check mechanism is introduced to identify and exclude low-quality observations, thereby mitigating the impact of gross errors. By exhaustively calculating the residual check metrics for all visible satellite combinations, the optimal set is dynamically selected to output three-dimensional fixed solutions. Field experiments verify that the method demonstrates significant advantages under severe electromagnetic interference, pronounced multipath effects, and low signal-to-noise ratio conditions.
Research conclusions: (1)A complete multi-system double-difference carrier phase filtering workflow was established, enabling high-precision processing from cycle-slip detection and clock jump correction to state parameter estimation and ambiguity fixing. (2)The posteriori-residual-based exclusion of low-quality satellite observations effectively reduces the adverse influence of gross errors on solution stability. (3) The adaptive satellite selection mode based on post-fit residuals proposed in this study can significantly improve the stability and reliability of positioning results in harsh monitoring environments such as strong electromagnetic interference, and can provide useful references for GNSS deformation monitoring under similar conditions.

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Prediction of Train-induced Vibration Response in a Large-scale Underground Rail Transit Hub Based on the Transfer Function Formulation

ZHAO Dou, YE Shaomin, LIU Peng, JIANG Bolong, LU Zhiting, LIU Weifeng

Journal of Railway Engineering Society. 2025, 42(12): 95-100.

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Research purposes: Taking a large-scale underground rail transit hub station as the research object, the vibration response in the underground rail transit hub station caused by the operation of high-speed railways and metro trains was predicted by using the transfer function formulation, and a comparative analysis was conducted with the calculation results of the traditional finite element model to study the applicability of the transfer function formulation for the vibration prediction in large and complex structures.
Research conclusions: (1) The transfer function formulation can be used for vibration prediction of large and complex structures caused by running trains, and it has good accuracy. (2) Compared with the traditional finite element method, the transfer function formulation has high calculation efficiency and is especially suitable for the calculation of vibration responses for large and complex structures under various train-track cases. (3) For the underground train vibrations, the vibration response of underground structure presents a vibration amplification zone along the sides of the track, which is caused by the vibration transmission characteristics of tunnel-soil-underground structure system. For high-speed railways and subway trains, the underground structure vibrations they generate exhibit significant amplitudes in the 40~60 Hz and 50~80 Hz ranges, respectively, which results from the characteristics of train-track dynamic interaction system. (4) These results can be applied to the vibration prediction and vibration-damping design of large-scale underground transport hubs. It lays a foundation for the vibration comfort assessment of building structures and the control of low-frequency noise along high-speed railway and subway lines.

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Research on Cross-Sectional Characteristics of Shield Tunnels in Urban Rail Transit at Different Speeds

CHEN Bing

Journal of Railway Engineering Society. 2025, 42(12): 101-106.

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Research purposes: In urban rail transit engineering, shield tunneling has become the mainstream construction method for tunnels in soft soil areas due to its low impact on the ground environment and its safety and efficiency. However, the cross-sectional size of shield tunnels directly affects the investment cost, construction difficulty, and long-term operational efficiency of the project, so conducting detailed research on it has significant economic and social benefits. This study aims to systematically explore the various controlling factors that affect the cross-sectional dimensions of shield tunnels, in order to seek an economically reasonable cross-sectional solution while meeting safety and functional requirements.
Research conclusions: (1) The height requirements for the overhead contact wire of DC rail transit are relatively low, and relatively clear and mature standards have been formed for the building clearance and shield tunnel section size. (2) The height of the overhead contact wire in the AC rail transit is significantly increased, resulting in greater installation clearance for the overhead contact wire and a larger tunnel structure gauge, leading to a significant increase in the cross-sectional diameter of the shield tunnel compared to the DC system. (3) By optimizing and adjusting the height of the overhead contact wire under the AC system, the installation height of the overhead contact wire can be moderately reduced, thereby reducing the tunnel structure gauge and inner diameter, effectively controlling the total project investment, and enhancing project economics. It has wide application value in the field of urban rail transit.

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Analysis of Vibration Source Intensity Characteristics in Small Radius Curved Sections of Subway Trains

ZHOU Shunxin, YANG Hongyi, SUN Kun

Journal of Railway Engineering Society. 2025, 42(12): 107-113.

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Research purposes: Impact of environmental vibration is one of the most critical influencing and concerned factors in environment impact assessment(EIA) of metro projects, this research, taking Suzhou Metro Line 3 as the research subject, conducts numerical monitoring of vibration source intensity on the ballast bed and tunnel walls in small-radius sections with curve radius less than 500 m. It aims to analyze the characteristics of vibration source intensity of metro trains in small-radius sections, and investigate the variation of environmental vibration impacts when metro trains pass through these sections, providing a basis for reducing environmental vibration impact in small-radius sections during actual metro operations and managements.
Research conclusions: (1) For sections with special vibration reduction measures (i.e., steel spring floating slab tracks), the vibration source intensity at the tunnel wall (in terms of Z-vibration level) was effectively reduced by 23.1 dB, however, the vibration source intensity at the ballast bed increased by 22.0 dB.(2) Monitoring results from the ballast bed and tunnel wall indicated three peak frequency bands for the Z-vibration level: 50 Hz, 63 Hz, and 80 Hz, with the maximum value primarily occurring in the 63 Hz band. (3) Within the tested train passing speed range for small-radius sections, the source intensity was negatively correlated with train’s operating speed. Specifically, under the same small-radius curve conditions, the higher the train’s operating speed through the section, the greater the probability of lower source intensity. (4) The lower the train’s operating speed relative to the design speed in small-radius sections, the more pronounced the cant excess phenomenon, leading to higher Z-vibration levels.(5)This research can be used in the EIA and measurement decision of urban metro.

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15 December 2025, Volume 42 Issue 12

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15 December 2025, Volume 42 Issue 12