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Research on Spatial and Temporal Distribution of Cooling Load of Subgrade in Permafrost Regions

HU Tianfei, YUAN Yifei, YUE Zurun, LIU Bei, ZHAO Liqi

Journal of Railway Engineering Society. 2026, 43(1): 1-6.

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Research purposes: Permafrost degradation can cause subgrade settlement, which is a main challenge for upgrading existing transportation routes and constructing new lines on the Qinghai-Tibet Plateau. Refrigeration technology can continuously output negative temperature throughout the year and input cooling capacity into permafrost foundations, making it a more real-time and effective type of permafrost protection measure. To ensure the rational design and energy-saving control of refrigeration systems, a cooling load calculation method for permafrost subgrades based on the Designer Simulation Toolkit for Building Environment (DeST) was proposed in this study. For an actual permafrost subgrade case, the temporal and spatial distribution patterns of its cooling load were calculated and analyzed, with the goal of maintaining the depth of permafrost table.
Research conclusions: (1) The cooling load starts at mid to late May, and ends at mid to late December, with a trend of first increasing and then decreasing over time, and is positively correlated with air temperature. The maximum daily cooling load is 169 W/m, lagging 12 days behind the peak daily air temperature. The average cooling load is 78 W/m. (2) The cooling load gradually decreases along the depth, with the maximum cooling load on the unit near the permafrost table, reaching a peak of 26.2 W/m. (3) The highest difference rate of monthly cumulative cooling load between the left and right half of the roadbed can reach 10.85%, showing a significant effect of sunny and shady slopes. (4) The yearly cumulative cooling load of the north-south oriented roadbed is the smallest, at 1 396 MJ/m, and its maximum difference compared to other orientations is 21.7%. (5) The results of this study can provide reference for the thermal state evaluation and refrigeration scheme design of subgrades in permafrost regions.

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Model Test and Numerical Simulation of Single Pile Bearing Characteristics of Screw-core Cement Mixed Pile

GAO Yue, YU Shaoshan, WU Luoan, XUAN Junjie, DU Yaohui

Journal of Railway Engineering Society. 2026, 43(1): 7-11.

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Research purposes: The spiral-core mixing pile, based on the rigid core pile technology, by improving the pile surface to a threaded design, enhances the interaction between the pile body and surrounding soil. To investigate the interaction mechanism among the pile core, the mixing pile shell, and the surrounding soil, a combination of model tests and numerical simulations was used to conduct single pile static loading tests. A bearing capacity model for single screw-core mixing piles was established under different thread height ratios w/d (ratio of thread width to screw-core inner diameter), and the effect of w/d on the pile's bearing performance was analyzed.
Research conclusions: (1) Compared with the traditional circular core mixing pile, the ultimate bearing capacity of the spiral-core mixing pile is improved by more than 40%, and the maximum settlement is reduced by over 40%. (2) Under relatively low vertical loads, both the pile core and the mixing pile shell share the load. As the load increases, the axial force gradually concentrates on the pile core, making the pile core the main load-bearing component of the cement mixing pile, with the screw core having a higher load-bearing capacity than the circular core. (3) Under vertical load, the settlement of the screw-core mixing pile decreases in a stepwise manner from the pile top to the surrounding area. Increasing the w/d ratio significantly improves the bearing performance of the screw-core mixing pile. (4) The results of this study can provide reference and guidance for railway embankment treatment and settlement control techniques.

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Stochastic Simulation Evaluation of the Stability of Sliding-collapse Dangerous Rock Mass

DONG Jiaxing, ZHANG Shengwei, WAN Junli

Journal of Railway Engineering Society. 2026, 43(1): 12-18.

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Research purposes: Rockfall disasters in the mountainous regions of southwestern China pose serious threats to the construction and operational safety of railway projects. Although uncertainty evaluation methods based on indicator systems offer an effective approach for analyzing dangerous rock mass stability, the values of evaluation indicators are inherently ambiguous, and constant weight allocations often fail to reflect the varying importance of influencing factors under different geological settings. To address this, an MCS-TOPSIS coupled model was introduced, integrating the G1 weighting method and variable weight theory to establish a stability evaluation model that accounts for uncertainties in both indicator values and weight assignments. The rationality and applicability of the proposed model were validated using two cases of sliding dangerous rock masses at the entrance of a railway tunnel in the southwestern mountains.
Research conclusions: (1) The MCS-TOPSIS model combined with variable weight theory effectively classifies the stability levels of dangerous rock masses and enables dynamic weight adjustment in response to changes in indicator scores. (2) Under the assumptions that indicator scores follow a normal distribution (Scheme 1) and a log-normal distribution (Scheme 2), the stability levels of both sliding dangerous rock masses are assessed as marginally stable. (3) The stability evaluation scores obtained from Scheme 1 are higher than those from Scheme 2, underscoring the importance of selecting an appropriate distribution type for indicator scores in model application. (4) The findings provide a methodological reference for stability analysis of dangerous rock masses in railway projects in southwestern China and other mountainous areas.

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Research on Evolution Law of Rail Wear on Small-radius Curve in Heavy-haul Railway

SHI Jin, GAO Yuxiang, LI Yuepeng

Journal of Railway Engineering Society. 2026, 43(1): 19-25.

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Research purposes: The surface condition and wear magnitude of rails serve as critical indicators for railway maintenance departments to implement repair operations such as rail grinding and replacement. Wear prediction facilitates the understanding of rail wear evolution trends and enables proactive formulation of maintenance strategies. Therefore, this study analysed the key characteristics and evolution patterns of rail wear across curves of varying radii and different rail positions, based on field-monitored wear data from the multiple maintenance cycles on a heavy haul railway.
Research conclusions: (1) The side wear of the outer rail in small-radius curves exhibits a "high in the middle and low at both ends" distribution, with the maximum wear occurring near the midpoint of the circular curve. Significant side wear is concentrated on the circular curve segment, while minimal wear is observed on transition curves. (2) As the curve radius increases, the monthly variation in both side wear and vertical wear diminishes during both the initial and later service phases. (3) A negative correlation exists between rail wear rate and curve radius, with side wear dominating the wear mechanism. When R≤800 m, the wear rate exhibits pronounced sensitivity to radius changes. For R>800 m, the influence of radius on wear rate becomes negligible, and the disparity between side wear and vertical wear rates progressively decreases.(4) The research results can lay a theoretical foundation for controlling rail wear and planning maintenance on sharp curves of heavy-haul railways.

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Multidimensional Evaluation of Spatial Geometric Alignment of Ballastless Track for Long-span Cable-stayed Bridges

CHEN Rong, PANG Tianqi, XUE Min, ZHOU Junhong, WEN Ming, WANG Ming, LV Tao

Journal of Railway Engineering Society. 2026, 43(1): 26-31.

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Research purposes: With the rapid development of high-speed railways,long-span bridges have been widely used in railways to meet the requirements of line smoothness and the need to span complex terrains.Due to the significant difference in stiffness between ballastless tracks and long-span bridges,problems such as poor adaptability of track structures and poor geometric alignment have emerged.Therefore,ensuring the safe operation of trains on ballastless tracks on long-span bridges has become an important issue at present.This paper took an actual engineering project as the research background and focused on the ballastless track on a long-span cable-stayed bridge with a main span of 688 meters and a designed speed of 160 km/h.It investigated the smoothness of track geometry from multiple dimensions and perspectives,including the frequency domain and time-frequency domain.
Research concluions: (1) Frequency domain analysis revealed that the irregularity energy under various operating conditions is primarily concentrated in long-wave frequency bands (wavelengths above 200 meters), with the train exerting the most significant impact on the vertical track alignment at the mid-span of the bridge. (2) Time-frequency domain analysis identified long-wave energy aggregation phenomena at mid-span (mileage 688 m) and beam ends (mileage 100 m), where energy mainly clusters in the wavelength range of 231.7-463.5 m and above.(3) The train-sensitive wavelengths differ significantly from the dominant irregularity energy wavelengths of the track, indicating that trains will not experience noticeable vibrations when traversing this long-span bridge.(4) Static geometric alignment analysis showed that track irregularity amplitudes predominantly occur near mid-span (688 m) and bridge tower regions (344 m).(5) Dynamic irregularity analysis demonstrated that overall temperature rise and drop conditions exert significant impacts on dynamic track irregularities.(6) This study provides valuable references for optimizing the design of ballastless tracks on long-span bridges.

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Identification of Ballastless Track Slab Deformation Based on Random Forest Model

GUO Gaoran, XU Hongbin, QIN Jie

Journal of Railway Engineering Society. 2026, 43(1): 32-38.

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Research purposes: Since the random forest model has the characteristics of fewer parameters, high classification accuracy and robustness to noise, this paper proposed an automatic identification method for ballastless track slab deformation of high-speed railway based on the random forest model. Firstly, monitoring data on the state of health and deformation of CRTS II ballastless track slab was obtained by using field tests. Secondly, empirical modal decomposition method (EMD) was used to decompose the track vibrations obtained in the field and the Pearson correlation coefficients were used to filter the derived intrinsic modal function components (IMFs) to obtain the characteristic IMFs, and the time-domain feature parameters of the characteristic IMFs were calculated as the initial feature vector matrix of the random forest model. Finally, the initial feature vectors of the ballastless track slab’s health and deformation states were imported into the random forest model for classification and identification.
Research conclusions: （1）A method for monitoring damage in the ballastless track structure on high-speed railway bridges based on wayside vibration was proposed, enabling real-time monitoring of the ballastless track structure on in-service high-speed railway bridges. By analyzing the measured wayside vibration signals, a time-domain feature extraction method based on EMD decomposition was employed to effectively extract deformation-sensitive features of the track slab.（2）The random forest model was used to classify and automatically identify the deformation state of ballastless track slab of high-speed railway, and the accuracy of automatic identification can reach 93.4%.（3）The proposed deformation monitoring method and intelligent identification method for ballastless track structures are also applicable to the monitoring and identification of defects in other civil engineering structures.

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Design and Sectional Parameter Analysis of a Novel Steel-Core-UHPC Composite Box Beam

WANG Lei, MENG Jie, QI Yong, CHEN Ruonan

Journal of Railway Engineering Society. 2026, 43(1): 39-45.

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Research purposes: Traditional normal concrete box beams are widely used in urban rail transit and regional railways. However, they suffer from heavy self-weight, which demands higher-capacity construction equipment and leads to significant long-term shrinkage and creep. Based on a project of a regional railway, this paper proposed a new steel-core-UHPC composite box beam, which features light self-weight, high load-bearing capacity, high sectional bending efficiency, and minimized long-term shrinkage and creep. The minimum plate thickness was determined based on local stability analysis. A finite element model was developed to calculate the stress and displacement of the composite beam. Sectional evaluation parameters were derived from mechanical theory. Furthermore, the effects of different plate thicknesses on the vertical deflection, stress, and overall bending efficiency were investigated.
Research conclusions: (1) The self-weight of the proposed composite box beam is only 55% of that of a normal concrete box beam, while its stress and displacement indices meet the design requirements. (2) The thickness of the top plate is positively correlated with the vertical deflection under self-weight and the stress in the bottom plate, but negatively correlated with the stress in the top plate and the sectional bending efficiency. The thickness of the web plate is positively correlated with the vertical deflection and the stresses in both the top and bottom plates under self-weight, yet negatively correlated with the sectional bending efficiency. The thickness of the bottom plate is positively correlated with the stresses in both the top and bottom plates under self-weight, but negatively correlated with the vertical deflection and sectional bending efficiency. (3) This composite box beam can provide a new structural form for bridges in urban rail transit or regional railways. The findings regarding the section parameters can serve as a basis for its practical application and further research.

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Effect of Deep-cutting Gorge Wind on Large-segment Erection of Stiffening Girder of Railway Suspension Bridge in High Elevation Mountainous Region

YE Huawen, LI Yanzhe, YANG Zhe, WANG Xiongjue, LEI Cong, LI Xin

Journal of Railway Engineering Society. 2026, 43(1): 46-53.

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Research purposes: The random variability of mountainous deep-cutting gorge terrain causes a 3D wind profile at bridge sites, and the complicated wind characteristics result in considerable risk to the construction of large-span suspension bridges. Based on the non-uniform wind characteristics in typical deep-cutting gorges, a linearly varying distribution model of equivalent static gust wind speed was firstly proposed for the stiffening girders. The erection of stiffening girders was then analyzed for the construction of a kilometer-span railway suspension bridge located in the deep gorges of a high-altitude region at the Sichuan-Tibet border. A spatial finite element model of the suspension bridge was also established to conduct reverse analysis during the erection stage of large-segment stiffening girders. A comparative analysis was conducted on the impact of non-uniform wind loads on the stress and deformation of key structural components, both in the reasonable completed bridge state and during the construction process.
Research conclusions: (1) The non-uniform wind loads have slight influence on the structural response of the suspension bridge during the large-segment erection process.(2) As the temporary connections between girder segments are primarily governed by vertical force control during large-segment erection, the non-uniform wind load has no effect on the the gap at the lower chord of the temporary hinges or the timing of achieving rigid connections.(3) However, compared to the uniform wind load scenario, the non-uniform wind load results in a 10% increase in axial forces and a double increase of shear forces at the temporary hinges, which necessitates careful consideration in the design of temporary hinges.(4) This research provides a reference for analyzing the impact of non-uniform gorge wind on structures during large-segment erection construction.

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Applicability Research on Small Span Steel-concrete Composite Girders for Heavy-haul Railways

CHEN Shuli, ZHANG Panhui, YANG Bo, LI Chen

Journal of Railway Engineering Society. 2026, 43(1): 54-59.

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Research purposes: To investigate the adaptability of small-span steel-concrete composite girders under heavy-load transportation conditions, this study took the replacement construction of a small-span beam in a heavy-load railway as the engineering background. Based on the operational performance inspection method, the study explored the dynamic response variations, such as vibration and deformation, of small-span beams under the passage of heavy-load trains. Numerical simulations were conducted to analyze the dynamic adaptability of small-span steel-concrete composite girders under higher speeds and greater axle loads. The findings aim to provide data support for the engineering application of small-span steel-concrete composite girders in heavy-load railways.
Research conclusions: (1) Under normal train operation, the dynamic response data of the steel-concrete composite girders, including mid-span lateral amplitude, lateral acceleration, vertical amplitude, and vertical acceleration, are significantly lower than those of the reinforced concrete beam, with a reduction ranging from 7.8% to 69.6%. (2) Compared with small-span reinforced concrete beams, the mid-span dynamic deflection of small-span steel-concrete composite girders increases under normal train operation but remains within the limits specified by design and inspection standards. (3) Numerical simulation results indicate that under a 35.0 t axle load train traveling at 90 km/h, the dynamic response of the small-span steel-concrete composite girders complies with current regulatory requirements. (4) The findings of this study provide valuable data support for the engineering application and research of small-span steel-concrete composite girders in heavy-load railways.

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Analytical Calculation of Hanger Cable Forces with Two Lateral Constraints and Its Application

WANG Lijuan, JIANG Ning, ZHANG Jiangong, LIU Xinyi, WANG Manping, LIU Shizhong

Journal of Railway Engineering Society. 2026, 43(1): 60-66.

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Research purposes: To address the significant errors in the frequency-based method for testing hanger cable forces when dampers are installed at both ends of a tied-arch bridge, this study first established the differential equations for the lateral vibration of hangers with two lateral constraints. An analytical model was derived to relate cable force and frequency to parameters such as the position and stiffness of lateral constraints. The nonlinear constitutive relationship of the rubber material in the hanger dampers was tested experimentally, leading to a model updating method capable of identifying lateral constraint stiffness. Using an 80-m through-tied arch bridge as a case study, a combined approach of experiments, MIDAS finite element analysis, ANSYS hanger simulation, and MATLAB computation was employed to comprehensively analyze the testing and calculation methods for hanger cable forces with two lateral constraints.
Research conclusions: (1) The theoretical cable forces under the action of two rubber dampers, obtained via the analytical solution, show errors that comply with code requirements when compared to the jack tension forces.(2) The proposed analytical method for calculating hanger cable forces can be effectively applied to tied-arch bridges equipped with two lateral constraints.(3) The findings provide a reference for accurate cable force testing in similar bridge structures with vibration control devices.

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Study on the Ultimate Turning Radius of Shield Machine Considering Over-excavation

ZHENG Yuchao, CHEN Shida, ZHU Binzhong, YAO Zhiwen, DAI Yongxing, TAO Lei, JI Yanlei

Journal of Railway Engineering Society. 2026, 43(1): 67-73.

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Research purposes: Clarifying the turning capability of shield machines is a crucial prerequisite for the successful design and construction of tunnels with small-radius curves. Currently, there is a notable lack of research on the turning radius of articulated shield machines. Based on the geometric characteristics of articulated shield machines during construction and the overbreak volume of profile cutters, this paper derived the functional relationships among the dimensions of single- and double-articulated shield machines, the articulation angle, and the turning radius, and conducted an analysis of related factors.
Research conclusions: （1）For single-articulated shield machines, the ultimate turning radius decreases approximately logarithmically as the articulation angle increases, with a more centrally located articulation mechanism resulting in a smaller minimum turning radius.（2）In double-articulated shield machines, the ultimate turning radius increases approximately linearly with the overall length of the shield, and the closer the length ratio of the front and middle shields is to 1, the smaller the turning radius.（3）Non-articulated, single-articulated, and double-articulated shield machines are all capable of negotiating small-radius curves, with the advantages of articulated and multi-articulated configurations becoming more pronounced when the articulation angle is fully utilized.（4）The research findings can provide valuable references and guidance for shield machine design and the construction of small-radius shield tunnels.

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SPH Simulation and Experimental Verification of the Friction-reducing Grouting Diffusion Mechanism in Rectangular Pipe Jacking

LI Peinan, LIU Yuqing, QIU Yan, ZHEN Liang, ZHANG Zhongjie, WANG Changhong

Journal of Railway Engineering Society. 2026, 43(1): 74-81.

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Research purposes: To solve the problem of low diffusion efficiency of friction-reducing grouting and easy siltation of slurry due to the geometrical characteristics of the rectangular pipe jacking with a super-large cross-section, this paper investigated how variations in certain component concentrations affect the performance of friction-reducing slurries. The smoothed particle hydrodynamics method,was employed to simulate the movement characteristics and diffusion patterns of friction-reducing grouting for large cross-section rectangular pipe jacking,elucidating the mechanisms governing slurry movement within the pipe-soil gap. Finally, by comparing the results of visualizing large-scale model tests, the plausibility of the numerical simulation results was verified.
Research conclusions: (1)The role of other additives can only be effectively performed when the bentonite content reaches 4% or more, in which CMC has a greater advantage in reducing the mud filtration loss rate, while HS-3 can significantly improve the dynamic shear force and thixotropy. PAM can enhance various performance indicators, but with a relatively gradual rate of improvement. (2) After injecting from the grouting hole, the friction-reducing mud will first flow down the trench and quickly fill the whole bottom surface, thus forming a layer of slurry-soil mixture on the bottom surface and effectively reducing the pipe-soil friction resistance. (3) During the initial grouting phase, it is recommended that the top and side grouting holes and the bottom grouting holes be grouted at the same time. During continuous jacking, with the continuous movement of the pipe sheet, it will cause changes to the contact morphology of the surrounding soil and the pipe sheet, and with the infiltration and loss of mud, it should be replenished in time to ensure the integrity of the grouting sleeve. (4) The research results provide theoretical support and data reference for the design and construction of rectangular pipe jacking project.

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Intelligent Design System for Shield Tunnel Segment Based on NSGA-II

LI Dong, WANG Ye, LI Qiming, FANG Qian, FU Gongyun

Journal of Railway Engineering Society. 2026, 43(1): 82-88.

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Research purposes: To achieve rapid design and scheme optimization of shield segments, this paper developed an intelligent design system for shield segments. The system encompassed seven modules: geological modeling, load calculation, structural design, reinforcement design, bolt design, waterproofing design, and design optimization. Through comparison with a design case of a shield tunnel section in Shenzhen Metro, the system has demonstrated reliability in load and internal force calculations, along with the capability to balance structural performance and cost considerations.
Research conclusions: (1) The automated shield segment design system integrates modules for geological modeling, load calculation, structural design, reinforcement design, bolt design, waterproofing design, and design optimization, enabling rapid segment design with limited input information.(2) A multi-objective optimization function is constructed based on the NSGA-II algorithm, balancing structural performance and cost.The optimal design parameter combinations are output through secondary optimization. (3) The system is applied and validated in an engineering case of a shield tunnel section in Shenzhen Metro, with relative errors of soil and water load calculations less than 6% and internal force calculations less than 5%.(4) The research findings provide valuable insights and references for the intelligent development of the rail transit industry's design sector.

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The Task System and Implementation Path of Digital Construction for Large-Scale Construction Enterprises

REN Jianxin, WANG Shengnan, ZHAO Yi, DU Hongbo, LIU Feng

Journal of Railway Engineering Society. 2026, 43(1): 89-93.

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Research purposes: Against the backdrop of the digital economy and policy-driven dynamics, digital transformation in the construction industry has become an inevitable trend. However, the overall level of digitalization in the construction industry currently remains relatively low, and large-scale construction enterprises are confronted with issues such as imbalances in technical adaptability, organizational synergy, and institutional guarantee. Integrating with the practices of digital construction in construction enterprises, this paper conducted research on the goals, overall framework, task system, and implementation path of their digital construction.
Research conclusions: (1) The two-phase goals of digital construction are clarified: the first phase is to consolidate the foundation of informatization, and the second phase is to activate new momentum of data resources.(2) An overall framework is constructed based on "four-chain integration" and a vertical-horizontal all-domain architecture.(3) This paper puts forward "four major tasks" and "two major supports" to clarify the content of digital construction.(4)It proposes the implementation paths of "chain supplementation", "chain strengthening", and "chain extension", a replicable model is established by building an independent innovation hub, promoting full-cycle digital-intelligent upgrading, and expanding business dimensions.(5) The research provides theoretical and practical paths for large-scale construction enterprises to enhance their core competitiveness and drive the high-quality development of the construction industry.

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Study on the Mutual Influence and Patterns Between Urban Roads and Rail Transit Linear Projects

LIU Minghui, DONG Ran, LU Zhuodan, JIA Siyi

Journal of Railway Engineering Society. 2026, 43(1): 94-100.

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Research purposes: The spatial overlap and mutual influence between urban roads and urban rail transit are crucial factors affecting the safety of urban transportation infrastructure. This study investigated a road-over-subway project in Beijing by developing an integrated model to simulate the impact of road construction on underlying subway tunnels and stations. Orthogonal experiments were conducted to analyze the sensitivity of structural displacements to parameters including soil compression modulus and burial depth.
Research conclusions: (1) Construction significantly influences vertical displacement of metro structures, with curved sections and locations under direct/eccentric pressure sensitive to vertical and horizontal deformation, respectively. (2) Vertical distance impacts displacement more than horizontal distance, with stations deforming less than tunnel sections and open-cut sections demonstrating higher safety.(3) Soil modulus and horizontal spacing mainly affect vertical displacement, while soil modulus and burial depth control horizontal displacement.(4) These results offer valuable references for similar projects.

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Research on Dynamic Control Method for Shield Tunneling Schedule in Subway River-crossing Interval

WANG Hui, MENG Xiaojing, NING Jinxuan

Journal of Railway Engineering Society. 2026, 43(1): 101-106.

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Research purposes: The subway river-crossing shield tunneling schedule is affected by complex, random, asymmetric, and multi-coupled factors, significantly increasing risks like delays and machine entrapment. To optimize progress control in river-crossing interval, this paper constructed a dynamic progress optimization control model integrating machine learning and visualization technologies to enhance the effectiveness of progress management for shield tunneling in river-crossing interval.
Research conclusions: (1) A spatio-temporal historical database of completed and ongoing similar projects is established. (2) The IGWO-SVR intelligent algorithm is used for static prediction and dynamic adjustment of the schedule. (3) Dynamic optimization control is achieved by combining DEMATEL and early-warning response methods. (4) The model’s scientific and practical value is validated through a real project. (5) The results provide a reference for schedule control in subway shield tunneling projects such as river-crossing intervals.

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Study on the Dynamic Mechanical Properties of PVA Fiber-EPP Concrete

WANG Mingsheng, LIU Yueyu, LU Junfu, XU Hongjun

Journal of Railway Engineering Society. 2026, 43(1): 107-113.

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Research purposes: To develop a tunnel isolation layer concrete material with excellent isolation and energy absorption performance, this paper explored the preparation process of a type of polyvinyl alcohol (PVA) fiber -expanded polypropylene foam (EPP) concrete. The split Hopkinson pressure bar (SHPB) test system was used to conduct impact load tests on PVA fiber-EPP concrete specimens. The experiment studied the influence rules of fiber content, fiber length, and EPP volume fraction on the dynamic mechanical properties, deformation and damage characteristics, and seismic energy absorption performance of the specimens.
Research conclusions: (1) The fiber content and length are the main influencing factors of the dynamic compressive strength of PVA fiber-EPP concrete. The dynamic compressive strength decreases as the EPP volume fraction and fiber content increase, and it first increases and then decreases with the increase of fiber length. (2) Based on the failure characteristics and dynamic stress-strain curves of PVA fiber-EPP concrete specimens, the dynamic stress-strain curves can be divided into three stages: the elastic stage, the plastic stage, and the failure stage. The PVA fibers play a bridging role inside the concrete, enhancing the toughness of the concrete specimens and transforming the failure mode of the specimens from brittle failure to plastic failure. (3) Based on the energy consumption analysis, the concrete with an EPP volume fraction of 50%, a fiber content of 0.7%, and a fiber length of 12 mm has the best vibration isolation and energy absorption effect under an impact air pressure of 0.06 MPa.（4） The research results can provide a theoretical basis for the application of PVA fiber-EPP concrete as a seismic energy-absorbing material in tunnels.

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LB Modeling and Study of Chloride Ion Erosion Characteristics in Concrete Track Slabs

PENG Zhigao, WANG Xinzhong, LONG Yanqing, XIAO Ming, LIU Wanghui, WU Di

Journal of Railway Engineering Society. 2026, 43(1): 114-120.

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Research purposes: Coastal high-speed railway concrete track slabs are susceptible to chloride ion erosion and present significant maintenance challenges. To address this engineering issue characterized by a complex mechanism and multiple influencing factors, this study employed the Lattice Boltzmann method to investigate the mesoscopic transport characteristics of chloride ions in concrete under multi-factor coupling conditions.By developing a multi-parameter coupling model, it comprehensively analyzed the influence of key factors on the chloride ion diffusion process, revealed the intrinsic patterns of chloride ion migration in complex environments, and provided a theoretical basis for the design and maintenance of high-speed railway concrete track slabs.
Research conclusions: (1) The dominant factors influencing chloride ion diffusion are loading frequency, stress level, temperature, humidity, and water-cement ratio.(2) The order of influence is stress level > temperature > loading frequency > water-cement ratio > relative humidity, with complex interactions among the factors leading to a multi-dimensional and non-linear diffusion mechanism.(3) Preventive measures to mitigate chlorideion erosion risks are proposed, including the use of high-performance concrete, control of the water-cement ratio, and comprehensive consideration of environmental factors and dynamic load effects.(4) The research results can serve as a reference for the durability design of high-speed railway concrete track slabs.

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Effects of High-speed Mixing of Bentonite Slurry on the Properties of Two-component Grout

WANG Shengwei, LI Yangjian, LU Bangbang

Journal of Railway Engineering Society. 2026, 43(1): 121-126.

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Research purposes: During the preparation of backfill grout for shield tunneling, the mixing of bentonite slurry leads to the transformation of water morphology and the delamination of clay particle crystalline layers. To investigate the effect of high-speed mixing of bentonite slurry on the engineering properties of two-component backfill grout, tests were performed on the engineering properties of the grout after high-speed mixing. Additionally, the mechanisms behind these effects were analyzed by measuring the electrical conductivity of the bentonite slurry and conducting X-ray diffraction (XRD) analysis on the hardened grout.
Research conclusions: (1) The bleeding rate and fluidity of the cement-based slurry decrease with prolonged high-speed mixing, whereas the setting time of the two-component grout first increases and then decreases. (2) The strength of the hardened two-component grout increases with extended curing age and high-speed mixing duration. (3) The electrical conductivity of the bentonite slurry increases with prolonged high-speed mixing, indicating a rise in bound water and a decrease in free water within the slurry.(4) High-speed mixing causes delamination of bentonite crystal layers, releasing montmorillonite platelets, which then participate in reactions with active substances in the slurry and contribute to pore-filling in the hardened grout.(5) The findings of this study offer valuable insights for improving the engineering performance of backfill grouts in shield tunneling applications.

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15 January 2026, Volume 43 Issue 1

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15 January 2026, Volume 43 Issue 1