Research purposes: With the basic formation of the "four vertical and four horizontal" and "eight vertical and eight horizontal" railway network, traditional railway construction technology has matured, but one map for the design, construction, construction, and operation and maintenance is still at the theoretical conceptual stage. The soft power in terms of fine design, full-monitoring construction, and intelligent operation and maintenance of railways is still a shortcoming, and it is also the fundamental bottleneck restricting the construction of independent digital railway engineering and intelligent railway system in China. With the rapid development of AI intelligence in the physical world, it is also an inevitable development trend for railway engineering to become collaborative, digital, and intelligent. In view of the current shortcomings of China's railway informatization, this paper proposes the concept of railway collaborative survey, design, construction, operation and maintenance system with one map of digital assets, the main idea is that the railway follows the technical context of digital earth and digital city, and uses the 3DGIS platform as the basic framework to build digital railway engineering assets and realize the expression of twin railways in computers.
Research conclusions: (1)The two-level evolution of "macro-micro" view constructed by GIS and BIM design has the characteristics of seamless connection of informatization in the whole stage and the whole process, loose coupling of spatial layout design and structural design, and single-scale static expression to multi-scale dynamic expression. (2) The digital asset application system centered on automated modeling of 3D route selection system mainly aims to solve the problem of universal asset access and realistic and efficient expression. (3) The construction of the "macro-micro" two-level evolutionary exploration and design system will greatly promote innovation in automated design. (4) The research achievement can lay the foundation for the forward BIM design,construction, and operation of railways.

Research purposes: Dolomite sanding is a special karst phenomenon, which is highly disaster-causing in water-rich environments. To reveal the cause of disaster caused by tunnel surge in water-rich sanded dolomite stratum, the control measures are provided. Based on the Jixin Tunnel from the Emei to Miyi section of the Chengdu-Kunming Railway capacity expansion project, this paper investigates the tunnel surge accident, analyzes the formation causes of white cloud sand by combining regional geology, indoor microscopic observation methods, and physical and mechanical tests, summarizes the disaster mode and causes of sanded dolomite, and puts forward control measures.
Research conclusions: (1) The regional dolomite sanding mechanism is a permeation-dissolution decomposition mechanical disintegration type, and the water-rich sanding sacs distributed in the formation are the disaster source of tunnel gushing. (2) Sanded dolomite is dominated by fine particles, poor uniformity, and significantly attenuated shear strength in water. Tunnel surge failure modes can be divided into penetration-type surge, progressive surge, and intermittent surge. (3) The disaster source identification, disaster source water pressure reduction, disaster source reinforcement, low disturbance excavation construction control countermeasures are proposed.(4) The research results can be applied to the control of tunnel water outburst disasters in sanded dolomite formation.

Research purposes: Accurate identification of tunnel lining surface cracks is essential for intelligent maintenance of railway infrastructure. To address the challenges of low accuracy and limited reliability in crack detection under complex railway tunnel conditions, this paper proposes a reliable and intelligent crack recognition method enhanced by image structural features and attention mechanisms, to support precise and rapid detection of crack-related defects in large-scale operating railway tunnels.
Research conclusions: (1)The reliable tunnel lining crack detection method based on the U-Net semantic segmentation architecture is developed.(2)Extensive experiments conducted on the large-scale public CrackSeg9K dataset demonstrate that the proposed method significantly outperforms existing crack detection approaches in terms of accuracy.(3)The designed feature fusion strategy, which integrates multi-structural image features and attention enhancement, effectively improves the accuracy and completeness of crack detection results.(4)The proposed method shows higher accuracy in detecting fine cracks and exhibits better cross-scene robustness, offering practical value for engineering applications in tunnel crack defect detection.

Research purposes: Investigation is the premise and foundation of planning, design, construction and operation of various infrastructure projects. China's infrastructure is constantly improving, and the process of urbanization is developing continuously. The Belt and Road Initiative for international cooperation is advancing in depth. The environmental challenges faced by engineering investigation are becoming more and more difficult, the implementation of traditional investigation methods is difficult, and the market competition in the field of engineering construction is more intense. All of these put forward higher requirements for the survey results and quality. In order to improve the level of investigation and survey technology, it’s very urgent and necessary to combine with cloud computing, big data, artificial intelligence and other new generation of information technologies. Through these all works, the digital transformation and intelligent upgrading of investigation technology can be realized.
Research conclusions: (1) Intelligent investigation is the comprehensive advancement stage of integrated survey technology development in the field of railway engineering (3.0 Era). (2) The main content of this paper is around the five main lines of investigation：information standard, data results, equipment means, operation process, and application service.The connotation of the technical system and the overall solution of the intelligent investigation of railway engineering are systematically established. (3) This paper shares the following research results: the survey information standard, the standardized mapping of remote sensing interpretation results, the rapid mapping of geological maps, the airborne multi-source remote sensing equipment, the multi-parameter test equipment in the hole, the intelligent remote sensing interpretation, the intelligent identification of core lithology, the rapid modeling of three-dimensional geology, the geological information service and the geological language model, etc. (4) The subsequent development direction is proposed in this paper, namely establishing standard systems, innovating survey equipment, upgrading specialized applications, enhancing collaborative services, and cultivating comprehensive talent. (5) These works can provide reference for the research of intelligent investigation technology, offering guidance for the whole industry and the various companies to advance digital transformation and intelligent upgrading of investigation technology.

Research purposes: Under the background of the Belt and Road Initiative, Chinese railway enterprises have achieved significant results in participating in the construction of international railway corridors, but they also face complex technical challenges. Taking a foreign railway project as an example, this paper systematically discusses the integrated application and innovative practice of China's railway surveying and mapping technology system in overseas projects.
Research conclusions: (1) A high-precision framework datum based on the WGS84 ellipsoid was established, solving the technical problem of low planar coordinate accuracy. (2) The "Sky-Air-Ground" integrated intelligent surveying and mapping technology was applied to achieve efficient data acquisition in complex topographic areas exceeding 2 000 square kilometers, with an efficiency improvement of over 60%. (3) A large-scene stereo model construction technology for aerospace satellite imagery was proposed, constructing a 3D real-scene model covering more than 7 000 square kilometers and innovating the traditional line route selection and geological surveying modes. (4) Based on the principle of "three networks integration", a full-domain high-precision engineering surveying control network was established to serve the entire lifecycle of surveying, construction, and operation and maintenance. (5) This study shows that through localization adaptation and technological innovation, China's railway surveying and mapping technology system has formed a solution that combines international universality and engineering applicability, providing a reusable technical paradigm for the overseas construction of Chinese railways.

Research purposes: The railway channel between the neighboring provincial capitals has gradually formed and presented a multi-line pattern. With the rapid development of regional social economy, the current situation of the channel has been difficult to meet the needs of channel transportation, and it is necessary to accelerate the construction and implementation of channel planning routes. Passgage planning route construction scheme selection is particularly important, not only to meet the rapid growth of the transportation needs of the channel, but also to achieve the maximum transport quality and transport benefits of the channel. Based on the Shanghai-Hangzhou railway channel and the Chongqing-Guizhou railway channel, this paper studies the route construction scheme of multi-line railway channel planning.
Research conclusions: (1) Railway passage planning should be adapted to the needs of regional social and economic development. (2) In-depth analysis of the status quo and existing problems of the railway channel, combined with the upper planning of the channel line, and scientific and reasonable determination of the construction plan of the planned line in the channel. (3) The railway channel planning line construction scheme should be coordinated with the overall standard of the channel to maximize the transport quality and transport efficiency of the channel. (4) This study can provide a reference for the selection of similar railway passage planning route construction schemes.

Research purposes: The anchor section joint is an important component of the catenary system and a core structure to meet the functions of electrical and mechanical sectioning for the catenary. According to different application scenarios, the types of anchor section joints for high-speed railways generally include five-span joints and four-span joints. Due to structural differences, different types of anchor section joints lead to significant differences in the pantograph lift and contact force between the pantograph and catenary when high-speed trains pass through, thus affecting the current collection performance. In severe cases, it may cause serious pantograph-catenary failures and impact transportation safety. Considering that both types of anchor section joints are currently applied in high-speed railways, studying the changes in pantograph-catenary contact force and pantograph lift under different types of anchor section joints is of great significance for improving the current collection quality of the pantograph-catenary and ensuring transportation safety.
Research conclusions: (1) When the train passes at high speed with double pantographs, the operating environment of the rear pantograph is harsher, with a larger variation range of pantograph-catenary contact force and a greater pantograph lift, making it a restrictive factor affecting the current collection quality of high-speed railways. (2) Regardless of the speed level of 250 km or 350 km, the five-span anchor section joint has superior overall current collection quality due to its smaller changes in pantograph lift and pantograph-catenary contact force. (3) The higher the speed, the higher the performance requirements for the catenary. For projects with a speed level of 350 km, the five-span anchor section joint should be selected. For projects with a speed level of 250 km, the five-span anchorsection joint is preferred, and the four-span anchor section joint can also be selected according to actual conditions. (4) The research results in this paper can be applied to the professional field of high-speed railway catenary.

Research purposes: At present, there are few research results on ultra deep circular diaphragm walls, and the understanding on its deformation characteristics lags behind engineering practice. This paper takes the south anchor ingot ultra-deep circular foundation pit of Qipanzhou Yangtze River Highway Bridge as the research object, and deduces the horizontal displacement formula by establishing the plane polar coordinate equation. FLAC^3D is used to establish a three-dimensional model with uneven geological conditions, and the overall mechanical characteristics and deformation rules of the circular diaphragm wall are compared and analyzed.
Research conclusions: (1)The calculated, monitored and simulated values of deep horizontal displacement vary little at the same depth, the bedrock has a significant anchoring effect on the diaphragm wall.(2)The variation law of circumferential stress is similar to the variation of deep horizontal displacement; the position of the maximum circumferential stress is close to the point of the maximum deep horizontal displacement.The transverse distribution of circumferential stress is relatively uniform and the transverse variation law of the maximum point of circumferential stress is similar to a cosine function.(3)The conclusion can provide reference for practical engineering applications and for the analysis of the mechanical properties and deformation law of super deep circular diaphragm walls.

Research purposes: Intense solar radiation in western mountainous regions caused longitudinally non-uniform temperature fields in the arch ribs of large-span deck-type arch bridges due to varying degrees of shading by the bridge deck system. This phenomenon brought challenges to structural design and operational maintenance. Based on the Fengjie Meixi River double-track arch bridge, temperature data were obtained from a bridge health monitoring system. Regression analysis was employed to investigate the longitudinal temperature distribution of box-section concrete arch ribs.
Research conclusions: (1) There is a significant temperature distribution difference along the longitudinal direction of the arch rib top plate, which presents a "V" shape. The temperature at the arch top is the lowest, and it gradually increases from the arch top to the arch feet at both ends. The maximum longitudinal temperature difference reaches 4.6 ℃. (2) The longitudinal temperature differences of the web plates and bottom plate are relatively small and can be regarded as uniform distribution. The maximum longitudinal temperature difference of the left web plate is 1.4 ℃, and that of the right one is 0.5 ℃. As the bottom plate is not directly exposed to solar radiation throughout the day, its longitudinal temperature distribution is relatively uniform, with a maximum temperature difference of 0.7 ℃. (3) The longitudinal temperature difference distribution of the arch rib top plate can be characterized by an exponential function form. The recommended model parameters are (4.2 ℃, -0.012) and (3.5 ℃, -0.01). This model shows high fitting accuracy in different observation periods and can effectively reflect the longitudinal temperature distribution characteristics of the arch rib top plate, having engineering application value.(4) The research results can provide theoretical support for the temperature effect analysis and structural performance evaluation of similar bridges.

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.

Research purposes: The Xiong'an-Xinzhou High-speed Railway is a critical transportation link between Xiong'an New Area and Xinzhou City in Shanxi Province, traversing complex terrains such as the Taihang Mountains. Particularly in the segment from Fuping to Wutai County, the steep terrain and significant elevation changes present major challenges in the design of long, continuous gradient sections. The slope design in this area must balance construction difficulty and investment costs while ensuring the operational safety and line capacity of the trains. This study investigates the impact of different gradient schemes on railway operation, aiming to propose an optimal gradient design for the Xiong'an-Xinzhou line and provide a reference for other high-speed rail projects in similarly challenging terrains.
Research conclusions: (1) Through a technical and economic comparison and simulation analysis of the 30‰ and 20‰ gradient schemes, the study recommends adopting the 30‰ maximum gradient scheme. This scheme demonstrates better feasibility in terms of construction and economics, aligning with local development planning needs. (2) Although the 30‰ gradient increases the maximum coasting speed of trains, it remains within the safety range, ensuring operational safety and meeting line capacity requirements. (3) The research can provide practical insights into the design and operation of high-speed railways in complex terrains and offer optimization suggestions to enhance operational efficiency and ensure safety.

Research purposes: In the design of high-speed railway bridges in western China, simple supported + rigid frame beam bridges with double block ballastless tracks are used. Aiming at the seismic design problem of such bridge structures, the response spectrum method is used to study the seismic response of each structural system by establishing the traditional calculation model, the wire bridge integrated model considering only the constraints of the track system and the constraints of both ends of the rail, and adjusting the number of rigid frame bridge spans and pier heights for different gully areas.
Research conclusions: (1) The restraining effect of the track system and the rails at both ends reduces the seismic response of the pier, but the restraining effect of the track system in the main bridge area will increase the pier bottom bending moment of the rigid frame edge pier, while the restraining effect of the rails at both ends of the bridge is small. (2) In the wire bridge integrated model, the energy dissipation capacity of rigid frame pier will be enhanced with the increase of the number of rigid frame bridges, but with the increase of pier height, the main energy dissipation components will gradually change to rigid frame edge pier. (3) The restraint effect of the track system will inhibit the pier top displacement of the whole bridge, but with the increase in the number of rigid frame bridges, the restraint effect will be weakened. (4) When the main span rigid frame is in one or three joints, the track stress is in the shape of "V" and "U" respectively, and the peak stress is located in the beam joint of the rigid frame edge pier, special design is recommended here to deal with stress concentration. (5) The research results can provide a scientific basis for the seismic design of high-speed railway bridges in western China.

Research purposes: In order to reveal the causal mechanism of accidents in complex mountainous railway tunnel construction, a dataset comprising 652 railway tunnel construction accident cases from 2013 to 2023 was collected. The FP-growth algorithm was employed to extract 161 association rules with high support. Based on these association rules, a hypergraph was constructed to model the causation network of railway tunnel construction accidents, and its topological characteristics were analyzed.
Research conclusions: (1) The accident causation network model based on the hypergraph clearly demonstrates the many-to-many relationships between risk events and factors, providing a powerful tool for further analysis of the complex relationships between risk events and factors in railway tunnel construction. (2) Among the six major categories of risk factors, personnel safety behavior, equipment configuration and usage, material testing are important in influencing the occurrence of events. In particular, surrounding rock stability and geological structure have a more direct impact on construction safety. (3) Rock bursts, collapses, and mud and water gushing are the most prominent risk events in the construction of complex mountainous tunnels. Factors such as geological forecasting, blasting techniques, surrounding rock stability, and complex geological structures have an important influence on these three types of risk events. (4) The research can provide a reference for the cause analysis of railway tunnel construction accidents in complex mountainous areas.

Research purposes: The terrain and geological conditions in the western mountainous areas of China are complex, with a large number of landslide-prone geological bodies. Currently, railway projects passing through landslide areas are mostly low-grade conventional speed ballasted track railways, which mainly focus on stability control and have low requirements for deformation control.Moreover, deformation repair is relatively easy. Effective subgrade structure and landslide reinforcement measures must be taken for high-speed railway embankments passing through landslide bodies to meet the requirements of subgrade stability and millimeter level deformation control. It is of great significance to reveal the stress and deformation characteristics and failure modes of subgrade reinforcement structures in landslide areas, and to propose design methods and reinforcement principles for high-speed railway embankments in landslide areas.
Research conclusions: (1)The high-speed railway subgrade in landslide areas should be stabilized and reinforced with a combination of foundation pile-slab structure and anti-sliding piles for deformation control.(2)Setting up rear anti-sliding piles has a significantly better effect on improving the stress and reducing deformation of the pile-plate structure than setting up front anti-sliding piles.(3)When the pile-plate structure is located in the anti-sliding section, the distance between the rear anti-sliding piles and the pile-plate structure should be 3~5 times the section length of the anti-sliding piles.When the pile-plate structure is located in the sliding section, the distance between the rear anti-sliding piles and the pile-plate structure should be 0.5~2 times the section length of the anti-sliding piles. (4) The cracks in the pile foundation of the pile-plate structure are mainly concentrated at the top of the pile and near the sliding surface, while the cracks in the anti-sliding pile are mainly concentrated near the sliding surface. (5) The principles and design methods for reinforcing high-speed railway embankments in landslide areas are proposed. (6) The research result can provide useful references for the construction of high-speed railways in landslide areas.

Research purposes:Achieving accurate carbon emission measurement in urban metro construction is crucial for implementing the "Dual Carbon" strategic objectives in the urban rail transit industry. Focusing on 21 stations of Tianjin Metro Line 7, this study employs a combined Principal Component Analysis (PCA)-Hierarchical Clustering (HC) algorithm to extract three principal components from 11 engineering attribute variables, systematically categorizing stations into four distinct types. Using the Life Cycle Assessment (LCA) methodology, the carbon emission patterns across material production, transportation, and construction phases were investigated for each station type.
Research conclusions: (1) Key findings reveal that Type C stations exhibit comparable carbon emissions from concrete and steel during material production, both serving as primary contributors, while concrete dominates transportation-phase emissions. For Type A stations, steel-related emissions during transportation significantly surpass those from concrete and cement. (2)During the construction phase, welding machinery emerges as the predominant carbon source for Type A and C stations, whereas "earthwork construction" and "welding machinery" contribute equally to carbon emissions in the other two station types. (3) Diverging from traditional approaches that adopt homogeneous carbon accounting for multiple stations, this study pioneers a refined emission calculation framework based on station-type differentiation, overcoming the limitations of conventional extensive carbon accounting models. The proposed methodology offers targeted insights for precise carbon reduction strategies in metro station construction.

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.

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.

Research purposes: Double-hole positioning assembly track slabs are increasingly being used in urban rail and regional railways due to their convenient construction, clear force transmission path, and good stability. To investigate the stress and deformation laws of the double-hole limited-slot track slab of the urban railway, and verify the bearing capacity and structural safety of the track structure, a 1∶1 full-scale experimental track slab model was constructed, and bearing capacity tests were conducted under longitudinal and transverse section loading.
Research conclusions: (1) Within the designed load range, the displacement of the track slab increases with the increase of the load, and no significant sudden changes were observed during the test process, indicating a good state of stress and deformation.(2) Under the longitudinal section test load of 29 kN, the maximum vertical displacement of the track slab is 0.896 mm; cracks initiate at 31 kN, and the maximum through-crack width at 40 kN is 0.17 mm, not exceeding the design allowable crack width limit, confirming compliance with longitudinal bearing capacity requirements.(3) Under the transverse section test load of 28 kN, the maximum vertical displacement is 2.751 mm, with a peak strain of 82.205 με; cracks initiate at 29 kN, and the maximum crack width at 32 kN is 0.21 mm, below the design allowable limit, indicating sufficient transverse safety margin.(4) During loading, the compressive strain at the lower edge concrete in both sections reaches a maximum of 212.37 με, far below the ultimate compressive strength limit of concrete, demonstrating stable performance in the compression zone.(5) The stress of the concrete around the limit hole of the track slab increases nonlinearly with the increase of load, and the strain increases by no more than 10 με compared to other measuring points on the same section. This impact on the overall strength weakening of the track slab is limited, and the track structure is safe and reliable.(6) The research outcomes provide experimental evidence for the design and optimization of double-hole positioning ballastless track slabs in regional railways.

Research purposes: During the tunnel excavation process, enhancing the advanced identification and comprehensive prediction of adverse geological conditions has significant engineering guiding significance. Based on macroscopic geological and hydrogeological analysis, a risk identification method for adverse geology in tunnels has been established. The risk levels are classified focusing on issues such as rock bursts under high ground stress, mud inrushes and water gushes, soft rock deformations, and high-temperature thermal hazards. The accuracy of the method is verified by taking the prediction of high-temperature thermal hazards as an example.
Research conclusions: (1) For advanced geological prediction, it is necessary to strengthen macroscopic geological and hydrogeological analysis, and pay attention to the combination of ground and tunnel interior, the combination of geophysical exploration and drilling, the combination of different geophysical exploration methods, and the combination of long-distance and short-distance predictions. The adverse geology identification method established in this paper is innovative and scientific. (2) A single prediction method is like "a blind man feeling an elephant", which can only reveal local geological conditions. Using comprehensive prediction means can deepen the overall understanding of adverse geology and reduce ambiguity. In practical applications, multiple anomalies should not be simply superimposed, and attention should be paid to the sensitivity of each method to geological problems. (3) Advanced geological prediction is an important guarantee for construction safety. Adopting effective risk identification methods helps to prevent the occurrence of various accidents and should be incorporated into the management of construction procedures. (4) This research can provide reference for the advanced identification of adverse geological conditions in tunnels and similar projects.

Research purposes: At present, China's railroad projects are mainly based on fixed prices, and the fixed price has a certain lag in response to the market environment and price fluctuations. The cost indexes obtained by analyzing the actual data of the project and the market can not only provide the time-sensitive market reference price, but also the data structure is more suitable for the informatization management of the cost. The purpose of this paper is to analyze the influencing factors of railroad project cost, establish the prediction model of railroad project cost, and put forward a method of compiling the railroad project cost index, to provide a theoretical basis and reference method for the establishment of market-oriented management mode of railroad project cost and the improvement of information management level.
Research conclusions: (1) Through literature research, survey research, and gray correlation analysis, the main engineering characteristic variables affecting the cost of railroad projects are derived. (2) The elastic network regression method is applied to establish the prediction model of railroad project cost, and the prediction error is less than 8% in the example validation, and the prediction goodness of fit is good. (3) By applying the railroad project cost prediction model based on elastic network regression, the railroad project cost indexes can be compiled in different periods and under different project characteristics, and can also be expanded to the compilation of corresponding project cost indexes based on construction drawing budgets and bidding quotations.

Research purposes: Aiming at the difficulty of dynamic early warning during the construction of tunnels with different levels of large deformation in extreme high ground stress environments, this paper, taking an extremely high ground stress soft rock tunnel in Sichuan as the engineering background, carries out quantitative research on ground stress inversion and the laws of large deformation of surrounding rock. A ground stress inversion program based on a genetic algorithm is developed to provide reliable ground stress boundary conditions for numerical simulation. Synergistic evolution curves of surrounding rock and support structures under different levels of large deformation are constructed, and through coupling analysis of the curves, dynamic early warning thresholds for surrounding rock stability are determined. The weight of displacement contribution rate is introduced to realize dynamic quantification of deformation contribution values of each step in different construction stages.
Research conclusions: (1) The intelligent inversion model of ground stress based on genetic algorithms integrates the geological tectonic field and monitoring data to achieve accurate reconstruction of the extremely high ground stress field with a 95% confidence level. (2) A surrounding rock-support co-evolution curve is constructed, the critical correlation between the cross-evolution node of the characteristic curve and surrounding rock instability is revealed, and the stability discrimination and early warning index is proposed. (3) A dual-control dynamic early warning system of "large deformation grade-construction stage" is proposed, forming a full-cycle decision chain of "monitoring-diagnosis-regulation", which provides a basis for ensuring the safety of tunnel construction and formulating practical early warning strategies. (4) The research results provide technical support for graded early warning and precise prevention and control of large deformation disasters during the construction of tunnels with extremely high ground stress, and offer valuable references for similar tunnel projects under complex geological conditions.

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.

Research purposes: At present, the waterproofing problem of the secondary lining circumferential construction joint mainly adopts the medium-buried waterproof material. However, during the construction process, problems such as twisting, floating, displacement and tipping of the waterstop often occur, making it difficult to ensure the construction quality. Therefore, this article adopts indoor experimental methods to study the waterproof effects of two new waterproof materials, cement-based permeable crystalline waterproof coating and non-oil permeable creep rubber waterproof coating, on the construction joints of the secondary lining of mining tunnels.
Research conclusions: (1) The type of waterproof coating and application method is closely related to the hydraulic strength, and need to be based on the hydraulic strength of reasonable choice. (2) Dust will affect the adhesion of waterproofing coatings and substrates, there is a dusty situation will significantly reduce the waterproofing performance. (3) Chiseling process on the non-oil-permeable creep rubber waterproofing coatings construction joints of impermeable performance of the influence of a small.(4) The research results can provide a reference for the development of waterproofing technology for the tunnel of the mining method as well as the control of the safety of tunnel support structure.

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.

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.

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.

Research purposes: This article takes the double-deck vehicle depot of Shenzhen Metro Line 15 and Line 29 as the research objects, and studies the key signal scheme for the connection line of the Tongle double-deck vehicle depot in response to the situation where the two lines adopt different signal systems. Starting from technical feasibility, engineering feasibility, and convenience of later operation, a "downgraded transfer operation mode" suitable for the Tongle double-deck vehicle depot interconnection line is proposed. Based on this, the outdoor signal equipment layout scheme, interlocking interface circuit scheme, and Automatic Train Supervision (ATS) construction scheme for the interconnection line are studied.
Research conclusions: (1) Given that there is currently no mature solution for the interconnection between TACS and traditional CBTC, it is recommended to adopt a downgraded mode of transfer operation for Line 15 and Line 29 at Tongle vehicle depot in the initial construction period. In the long term, the signal systems of Line 15 and Line 29 can undergo interconnection construction with the background of major repairs and renovations.(2) The outdoor signal equipment layout and interlocking interface circuit scheme proposed in this article can achieve key control functions such as hostile route inspection, section status display, and switch status acquisition on the interconnection line, meeting the safety operation requirements of the interconnection line.(3) To ensure the smooth implementation of the project, it is recommended to adopt the independent construction of vehicle base ATS scheme for Line 15 and Line 29 during the initial construction period.(4) The research results of this article can provide a reference for the implementation of double-deck vehicle depot projects under different signal systems.

Research purposes: High-speed rail (HSR) plays a crucial role in fostering China’s new development paradigm and promoting high-quality growth. To address the dual challenges of expanding debt and stagnant operational efficiency of China’s HSR, this study constructs a “cost reduction-revenue expansion-sustainability” analytical framework. It employs the activity-based costing method to meticulously analyze the cost constitution, utilizes break-even and sensitivity analysis approach to identify key profitability drivers, and quantitatively evaluates HSR’s comprehensive advantages based on the “Energy-Economy-Environment” (3E) theory.
Research conclusions: (1) The average operational cost of China’s HSR is 0.372 yuan/ (passenger -kilometer), with capital cost (46.15%) as the dominant component, followed by transportation cost (36.16%). (2) The daily train densities required to achieve cash-flow balance and full cost break-even are 25 and 84 respectively. (3) Sensitivity analysis reveals that increasing the occupancy rate is the most effective factor in lowering the break-even point, followed by reducing construction costs. (4) Key pathways for enhancing operational efficiency include: implementing refined life-cycle cost management, diversifying revenue streams, and leveraging the comparative green advantages of HSR. (5) The study findings provide valuable references for HSR investment and operational management, thereby contributing to the sustainable development of the HSR in China.

Research purposes: With the continuous advancement of tunnel engineering in complex geological conditions in western China, water and mud inrush during mountain tunnel construction has become increasingly frequent and severe. Among these disasters, time-lag inrush events characterized by suddenness and hysteresis pose significant challenges to construction safety due to their pronounced spatio-temporal uncertainties. This paper analyzes the formation environments and process mechanisms of recent time-lag water and mud inrush events in mountain tunnels, proposes their definitions, classifications, detection and prediction technologies, and establishes a set of reliable risk identification and prevention measures for field construction.
Research conclusions: (1) Time-lag water and mud inrush events can be classified into three categories based on spatio-temporal characteristics: water gushing-piping type, flow soil-collapse type, and composite type.(2) High-risk zones for time-lag inrushes typically exhibit disaster-prone environmental features such as surface negative topography, structural fracture zones, low-resistivity anomaly regions in geophysical surveys, and minor angles between maximum principal stresses and negative topography/structures.(3) A semi-quantitative evaluation method was developed to assess risk levels (Levels I,II,and III) and probabilities of time-lag inrush, considering factors including rock fragmentation, water outflow state, primary support conditions, and construction collapse impacts.(4) Prevention strategies should follow the principle of "prioritizing robustness over weakness and ensuring one-time pass-through". Key measures include extended detection range, long-distance pressure relief, graded reinforcement techniques, and hierarchical risk mitigation for hysteresis hazards.(5) The research results can provide references for predicting and controlling time-lag water/mud inrush in similar complex geological settings.

Research purposes: A large number of newly-built railways use frame piers to cross the operational railways. Traditional frame piers have a long construction period, and there is a risk of overturning and falling objects in the brackets and templates, which has a significant impact on the operation of railways. In order to ensure the safety of railway operations, a new type of structure is studied to reduce construction interference and safety risks. This paper proposes new frame piers and connection structures such as steel-concrete composite columns, integral steel columns,steel-concrete hybrid columns, and conducts theoretical calculations, finite element analysis, and experimental verification to grasp their mechanical properties and meet engineering application requirements.
Research conclusions: (1) The new frame pier column and foundation are connected by a combination of steel bars, studs, and bolts. The outer connecting steel bars and studs provide the highest resistance bending moment in the connection structure, followed by the connecting bolts. The sum of the two accounts for approximately 80%~85% of the total bearing capacity. (2) Through refined finite element numerical analysis, under normal operating conditions, the components of the connecting structure are in an elastic state and meet the stress requirements under the calculated load. (3) The results of the 1∶4.5 scaled model quasi-static test show that the failure mode of the new frame pier is the bulging of the pier body steel plate. The joint structure and pier body have good collaborative stress performance, and the horizontal bearing capacity of the structure is controlled by the strength of the pier body; Compared with the theoretical calculation values, the experimental cracking bending moment is 1.47 times the maximum bending moment under normal operating conditions, and the yield bending moment is 1.27 times the maximum bending moment under seismic action. The connecting structure has good static and seismic performance. (4) The reseach results can provide reference and inspiration for the design and construction of railway frame piers.

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.

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.

Research purposes: Large-span suspension bridges have relatively low structural stiffness and damping, resulting in more pronounced wind-induced vibrations. To study the mechanism of static wind instability of a spatial four-cable suspension bridge, and to understand the influence of spatial cables and hanger system on static wind stability, a three-dimensional nonlinear static analysis of a spatial four-cable suspension bridge with a main span of 2 100 m was carried out by using ANSYS to establish a finite element model. The stress changes of inward inclined hanger and vertical hanger during static wind instability are investigated, and the effect of the hanger system on the static wind instability of a spatial four-cable suspension bridge is studied.
Research conclusions: (1) The stress on the inward inclined hanger acting on the centerline of the main girder is more affected by lateral displacement than that on the vertical hanger. Increasing the stress on the inward inclined hanger can enhance the vertical stiffness of the suspension bridge and reduce the vertical displacement of the structure. (2) Inclined hanger shares part of the structural gravity that does not provide torsional stiffness,and such spatial cable systems can harm the static wind stability of suspension bridges prone to torsional instability. (3) The mechanism of static wind instability in spatial four-cable suspension bridges is as follows: as wind speed increases, the rapid increase in the additional wind attack angle leads to a rapid increase in the effective wind attack angle. Since inward-inclined hangers do not provide torsional stiffness, changes in their stress directly affect the stress magnitude of vertical hangers that provide torsional stiffness, thereby accelerating the growth rate of the additional wind attack angle. The rapid development of main girder torsion and vertical deformation causes the stress in the hanger at the midspan, which is less constrained, to drop sharply and become relaxed. When the torsional stiffness provided by the cable system is insufficient to resist the torsional forces generated by static wind, static wind instability occurs. (4) The study of static wind stability in spatial four-cable suspension bridges with inward-inclined hangers can provide a reference for the design of spatial cable systems for large-span suspension bridges.

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.

Research purposes: With the increasing development of tunnel engineering toward greater burial depths and longer distances, the Tunnel Boring Machine (TBM) has been widely adopted due to its advantages of high automation, minimal environmental disturbance, and high construction efficiency.However, in hard rock strata, TBM performance struggles to align with the encountered geological conditions. Adjustments to key boring parameters are predominantly dependent on operator’s experience, and there is a lack of effective rock fragmentation optimization strategies. This frequently leads to impeded advance rates, overloading of cutting tools, and significant project delays. Therefore, based on CSM model a Simplified CSM Model (SCSM) is proposed to express the relationship between tunneling parameters and geological environment. According to the limit performance constraints of equipment thrust, torque and slag discharge, the feasible region of tunneling parameter optimization problem is partitioned, and the optimal control parameters are solved by multi-mode.
Research conclusions: (1) Based on field tunneling data from the ​Yinsong Project, a critical thrust empirical formula is derived via linear fitting. Based on the Hanjiang-to-Weihe River Project, a rock-breaking mode zoning model is established by incorporating critical thrust and the FPI (Field Penetration Index). Within the partitioned feasible domain, ultra-hard rock is defined according to TBM performance limits, and optimization strategies,including a ​rock abrasion mode for ultra-hard rock and tailored approaches for schist and mixed modes are proposed. (2)Applied to the section K29+169.2~K33+613.1of the Hanjiang-to-Weihe River Project-Lingnan Section, the proposed strategies reduce tunneling energy consumption by 5.5% and significantly improve progress. (3) Results demonstrate that the multi-modal parameter optimization strategy fully exploits TBM performance in medium-to-low strength rocks, while enabling multi-objective optimization balancing schedule and energy efficiency in ultra-hard rock conditions.

Research purposes: The damage to tunnel structures under earthquake action mainly occurs in fault sections. To study the longitudinal earthquake response characteristics of cross fault tunnels under earthquake action, firstly, based on the Pasternak dual parameter elastic foundation beam theory, a mechanical model for the longitudinal earthquake response of cross fault tunnels was established and theoretical analytical solutions were obtained; Secondly, the rationality of the theoretical solution was verified by using numerical calculation methods; Finally, the dynamic response laws of structural stiffness, wave velocity ratio, and fault width on the displacement and internal forces of tunnel structures were discussed.
Research conclusions: (1)The longitudinal earthquake response mechanical model of the cross fault tunnel is reasonable, and the maximum error of the theoretical solution does not exceed 3%, which can be applied to practical engineering design. (2) The increase in structural stiffness reduces the displacement of the lining within the fault range and increases the internal force of the structure.(3)The displacement and internal force of the lining show an increasing trend with the increase of wave velocity ratio.(4)The increase in fault width increases the displacement of the lining and reduces stress concentration.(5)In practical engineering, it is recommended to use gradient grouting method to reinforce the rock mass near the fault width of 4~5 times, in order to improve the anti fault ability of cross fault tunnels. (6)The research conclusion can provide theoretical basis for seismic design of cross active fault tunnels.

Research purposes: At present, research on the whole-process cost control system based on cost information and data is relatively rare, and the research on the nonlinear prediction and control of the engineering investment target needs to be further deepened.In view of the unavoidable investment overrun problem of large-scale construction enterprises' construction projects, this paper takes a large-scale construction enterprise's housing construction project as an example, and comprehensively integrates cosine similarity algorithm, BP neural network, saliency theory, earned value method and PDCA cycle,to achieve the effective control of investment in construction projects for large construction enterprises.
Research conclusions: (1) From the perspective of the engineering construction enterprise, making full use of the advantages of large construction enterprises,including rich construction experience and sufficient historical cases, this study establishes a database of completed projects of large construction enterprises, providing a basis for subsequent research. (2) By adopting the cosine similarity algorithm, BP neural network and saliency theory, this study constructs a three-level prediction model for construction project investment targets from three perspectives: total investment target, sub-item project and measure project investment target and labor cost, material cost and construction equipment use cost investment target , improving the accuracy of investment target forecasting.(3) Using earned value method and PDCA cycle management concept, dynamic analysis and optimization of significant sub-item project investment targets is achieved, and the establishment of a graded early warning system for investment deviations enables effective construction project investment control.(4) This study can provide reference for large construction enterprises' construction project investment control.

Research purposes: To explore the unloading-collapsibility characteristics of loess between piles in collapsible loess composite foundations, this study establishes a computational model for unloading-collapse deformation of inter-pile loess by employing characterization parameters of the unloading-collapse process and a reduction equation for loess deformation modulus. The stress distribution and collapse deformation characteristics during the unloading-collapse process are analyzed, and new opportunities for engineering applications are broadened.
Research conclusions: (1) Vertical stress in inter-pile loess during unloading-collapse shows a decrease-increase-decrease trend, with diminishing reduction effect beyond critical pile spacing. (2) Accounting for unloading-collapse effects allows reducing neutral point depth, improving upon conservative traditional estimates. (3) The practice of blindly crossing or removing the collapse soil layer is economically inefficient. It is recommended to control collapse deformation of the site by adjusting pile spacing. (4) This study can provide a theoretical basis for support optimized stability assessment for high-speed rail subgrades in loess regions, enhancing cost-effectiveness and safety.

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.

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.