Research purposes: Bolt anchoring is an important method for the prevention and control of engineering rock masses, especially in deep engineering. Its research has significant theoretical and practical implications. In view of the deficiencies in the research on the pre-tension of bolts in hard rock, gabbro anchor body specimens with different anchoring lengths were prepared, a bolt pre-tension monitoring system was developed, bolt pre-tension relaxation tests and uniaxial compression tests with different anchoring lengths were carried out, a pre-tension relaxation model was established, and the pre-tension contribution degree was defined.
Research conclusions: (1) As the anchoring length increases, the degree of pre-tension attenuation and loss is lower, and the effect of the pre-tension support control is more obvious. By monitoring the pre-tension, the anchoring quality can be analyzed and judged. The poorer the anchoring quality, the faster the pre-tension relaxes and the greater the relaxation amount. (2) In the elastic stage, the bolt pre-tension changes in a nearly linearly positive correlation with the applied load. The bolt pre-tension relaxes synchronously with the vertical stress. The processes such as the loading and relaxation of the surrounding rock in engineering can be reflected in real time by monitoring the pre-tension. (3) For the pre-peak load under uniaxial loading, as the load increases, the pre-tension of the fully grouted bolt undergoes stages such as slow increase, accelerated growth, and sudden increase. The accelerated growth and sudden increase of the pre-tension of the pre-peak load are directly related to the evolution of the damage and fracture of the surrounding rock of the anchor body. By monitoring the pre-tension, the internal evolution process of the anchor body and the surrounding rock can be grasped. (4) The post-peak load under uniaxial loading shows a process from gradual decline to sudden drop, and the pre-tension shows a process from continuous increase to sudden increase and then sudden drop. The change of the pre-tension is directly related to the evolution of the damage and fracture of the surrounding rock of the anchor body. By continuously monitoring the pre-tension, the rock mass failure and the occurrence of dynamic disasters can be predicted. (5) The pre-tension relaxation model has a good fitting effect and only requires two fitting parameters. The relaxation characteristics of the pre-tension can be well reflected and the relaxation process can be predicted through the quasi-viscous coefficient or the order value. (6) The lower the maximum contribution degree value at the time of failure, the worse the anchoring effect, and vice versa. The contribution degree can comprehensively reflect the anchoring quality, the contribution degree, and the working state. (7) The research results have guiding and reference significance for the anchoring mechanism, monitoring, prediction, and the mechanism, prevention and control of rock bursts of prestressed bolts.

Research purposes: In order to explore the characteristics of independent pore changes in railway saline soil subgrade under freeze-thaw cycles, industrial CT scanning, shear testing, particle size analysis, and mud content measurement methods were used to analyze the independent pore structure, volume, and quantity changes of saline soil samples with different moisture contents after freeze-thaw cycles.
Research conclusions: (1) The number of independent pores inside saline soil samples does not increase with the increase of moisture content after multiple freeze-thaw cycles; After undergoing different freeze-thaw cycles, samples with different moisture contents have the highest number of independent pores within the volume range of 0~5×10⁸µm³, and the lowest number of independent pores within the volume range of 5×10⁸~1×10⁹µm³. (2) When the moisture content is greater than 6%, after several freeze-thaw cycles, the independent pores inside the sample evolve into interconnected pores. (3) Under the freeze-thaw cycle, there is a significant variation in the independent pores of saline soil samples with different moisture contents. The changes in moisture content and temperature of saline soil are the direct causes of changes in the volume, quantity, and location of independent pores. (4) The research result can provide a basis for the prevention and control of expansion disasters in railway saline soil subgrade.

Research purposes: Aiming at the issue of excessive carbody vibration acceleration in 380A trains when passing through specific turnouts, this study aims to collect data on train wheel and turnout rail profiles, develop and implement detailed grinding strategies, and investigate the impact of grinding on train dynamic characteristics through a combination of simulation and field testing, so as to enhance the operational stability of trains passing through turnouts.
Research conclusions: (1) The study found that multiple train wheel sets exhibit polygonal wear, flat scar wear, and pit wear, while high-speed turnout rails show various forms of degradation, significantly affecting train dynamic characteristics. (2) To improve work efficiency, the target grinding profiles are simply optimized to meet practical grinding requirements. (3) Simulation results from the vehicle-turnout coupled dynamic model indicate that after grinding, the maximum values of wheel-rail lateral and vertical forces are reduced by 45.79% and 15.40%, respectively; and the maximum values of carbody lateral and vertical accelerations are reduced by 36.96% and 30.00%, respectively. (4) Field measurement data show that after grinding, the maximum lateral acceleration of the train carbody passing through the turnout is reduced to 0.64 m/s², a decrease of 55.86% compared to before grinding; the maximum values of wheel-rail lateral and vertical forces are 34.51 kN and 152.47 kN, respectively, a reduction of 42.82% and 17.38% compared to before grinding. (5) Grinding of turnouts can effectively improve the dynamic characteristics of trains under wheel wear conditions, which has practical application value for enhancing the operational stability of high-speed trains.

Research purposes: The railway gauge rod can improve the railway track's horizontal stability, enhance the ability to control the gauge, and ensure operation safety by connecting two rails through a gauge rod. This paper systematically investigated and summarized the application of railway gauge rod products, and analyzed problems of current products designed according to current codes. By interpreting the principles and thoughts of new codes, TB/T 1780—2023, Railway Gauge Rod, the improvements in terms of parts, and critical indicators were presented. The revision of the code was summarized.
Research conclusions: (1) There are two types of railway gauge rods, general railway gauge rods and insulated gauge rods. The corresponding codes are TB/T 1780—1986 General Railway Gauge Rod and TB/T 2492—2004 Technical Specification for Insulated Gauge Rods. (2) Current railway gauge rods have problems including the bending of rods, the cracking of clips, the interference of sleeves and rails, the weak insulation performance, etc. It is necessary to improve critical indicators for the users. (3) With the rapid development of the heavy-haul railway, the rod for 75 kg/m rail is suggested with a radius of 38 mm, and 350 kN is adopted for the test load of tensile strength. (4) QT450-10 is suggested for the steel clips and #45 Steel is suggested for the rods. The minimum thickness of insulation is suggested to be 5 mm. The length of the rod should be designed according to practical use. (5) This paper systematically analyses current codes and products for railway gauge rods and summarizes the revision process, which could be design references for future railway track reinforcement products.

Research purposes: This paper takes the Sichuan Kahlo Jinsha River Bridge, a 1 030 m span suspension bridge in a high-intensity earthquake-prone mountainous area, as the research background. In response to the economic decline caused by the large seismic response and structural size of traditional reinforced concrete bridge towers, four types of bridge tower schemes, including steel structure, steel tube concrete structure, reinforced concrete, and new steel tube concrete composite column, are compared and selected. A reasonable suspension bridge tower structure form suitable for strong earthquake-prone mountainous areas is proposed, and its key structures are discussed and analyzed in detail.
Research conclusions: (1) The seismic force of a single-span double-hinged suspension bridge tower mainly comes from itself. (2) The concrete-filled steel tube composite tower is lightweight, and the seismic response is greatly improved compared with the concrete bridge tower. (3) The concrete-filled steel tube composite column bridge tower scheme is simple in structure, reasonable in force, and good in construction implementability. In structure, it is necessary to focus on solving the problem of force transmission at the top and bottom of the column. The key factor is that the core concrete is under three-way compression. (4) The results of this study can provide a reference for the tower design of long-span suspension bridges in high-intensity areas.

Research purposes: Concrete bridges undergo non-linear temperature distribution within their internal temperature field during heat exchange with the external environment, influenced by ambient temperature and solar radiation. To investigate the temperature distribution characteristics of simply supported box girder bridges considering the effect of ballastless track cover, a thermodynamic simulation model was established, taking into account date, time, and external temperature. The accuracy of the computed results was validated using experimental data. The variation of box girder temperature fields at different times under sunlight exposure was analyzed, and the impact range and patterns of the ballastless track cover's effect on the temperature field of simply supported box girders were explored.
Research conclusions: (1) Under sunlight exposure, the amplitude of daily temperature difference on the bridge deck varies closely with the distance from the surface, with greater variations closer to the surface. (2) When the ballastless track is considered, the temperature of the beam body under the ballastless track is generally reduced, and the maximum temperature reduction of the beam body at the same position can reach 20.19%. (3) As the distance from the ballastless track increases, the influence of the cover effect on the girder temperature gradually weakens. (4) Within 4.86 m lateral distance from the centerline of the girder top slab, the ballastless track cover effect is significant, affecting both vertically and horizontally to a large extent. Within 2.12 m distance from the top slab surface on the web, the effect of the ballastless track cover is significant, while the effect on the bottom slab is relatively small. (5) The influence pattern of the ballastless track cover's effect on the temperature change of the girder body is similar to the distribution pattern of temperature change. The top slab is most affected vertically, while horizontally, the main impact is on the girder body directly beneath the ballastless track. (6) The findings of this study can provide a theoretical basis for optimizing the control of temperature effects on bridge girders in ballastless track design.

Research purposes：Static acceptance is one of the crucial stages in the completion acceptance of high-speed railway. The field inspection during the static acceptance of bridge engineering involves numerous inspection points and a significant workload, and its progress directly impacts the subsequent dynamic acceptance. The handling of issues identified is also closely related to the long-term service performance of the bridges. In order to improve the current practice where static acceptance mainly relies on manual inspection, this paper conducts data cleaning and reconstruction analysis based on static acceptance reports from four high-speed railway bridge projects. Furthermore, it explores a novel field inspection methods framework that integrates unmanned aerial vehicles (UAVs) and information systems.
Research conclusions：(1) Field issues exhibit a multi-level distribution characteristics ranging from macro, meso, to micro levels. Based on the current methods of summarizing and describing issues, it is not effective to conduct high-value analytical applications on the issue set. (2) The representation of field issues has been standardized, clarifying the hierarchy of 13 major inspection categories and corresponding sub-categories. The standardized issue database has been established. (3) The top five categories of issues are waterproofing and drainage, external environment, protective facilities, security inspection facilities, and bridge deck accessories, accounting for 29.9%, 18.9%, 18.4%, 13.1%, and 12.3% respectively. The distribution of issues follows a Pareto distribution. (4) Using UAVs, it is possible to inspect 40% of the field issues. (5) The reconstructed framework for field inspection procedures integrates applications across multiple scenarios, including UAVs, information systems, and on-site inspections, which can provide reference for further enhancing the effectiveness and efficiency of static acceptance in bridge engineering.

Research purposes: The characteristics of granite residual soil softening and collapsing when encountering water, as well as dehydration and drying shrinkage, pose great difficulties for deep foundation pit excavation construction. This paper takes the granite residual soil deep foundation pit project near a subway tunnel as an example, summarizes the deformation of the foundation pit, groundwater level, and various monitoring data of the tunnel during excavation, analyzes the reasons for tunnel settlement and abnormal decrease in groundwater level, and compares the effect of different control measures on the deformation control of adjacent tunnels.
Research conclusions: (1) The maximum cumulative settlement induced by excavation of the foundation pit in the adjacent tunnel is 44.5 mm, and its impact on construction in granite residual soil areas should be taken seriously. (2) The significant decrease in groundwater level is the main reason for the softening and collapse of the residual granite soil layer, and it is also an important reason for the excessive deformation of adjacent tunnels. (3) During the excavation of the foundation pit in the residual granite soil layer, support should be erected as soon as possible to reduce the exposure time of the foundation and control the deformation of the retaining structure. (4) According to the inversion calculation results, after excavation and dewatering of the foundation pit, the compressive modulus of residual soil is only 44.0% of that before excavation. After WSS horizontal grouting reinforcement, the compressive modulus increases by 3.8 times, the maximum settlement displacement of the tunnel was restored to 77.1%, and the maximum horizontal displacement was restored to 53.6%, and the amplitude of secondary settlement in the tunnel after compensation reinforcement is significantly reduced. (5) This research result can provide reference for excavation of foundation pits near tunnels in areas similar to granite residual soil.

Research purposes: With the acceleration of urbanization, the number of projects of shield underpassing existing railroad bridges is increasing. To analyze and judge the safety of shield structure under the railroad bridge, the random field theory based on Gaussian autocorrelation function and Karhunen-Loève (K-L) level expansion method is adopted, the spatial variability and autocorrelation of the ground soil are taken into account, and a refined three-dimensional finite element model is established for stochastic analysis, and the results of the analysis further give an analytical method and countermeasures for the safety of shield structure under the railroad bridge. The analyzing method and countermeasures are given to the safety of shield structures under railway bridges.
Research conclusions: (1)The random field theory can be better applied to the analysis of rail deformation of shield structure underneath the existing railroad bridge; Compared with the deterministic analysis, the stochastic curve obtained by the stochastic analysis method can more fully characterize the process, trend, and deformation range of rail deformation, reflecting the effect of the stochasticity of the soil parameters on the deformation of the rail. (2)This paper gives the probability of rail deformation exceeding the standard under different control values and the speed limit value of traveling under different stages of construction, to ensure the safety of traveling under the construction stage. (3)The research results can be better applied to the shield structure under the railroad bridge and other fields.

Research purposes: China will build a large number of railway tunnel projects in the western region. Construction ventilation is one of the most important factors restricting the selection of routes and auxiliary tunnels for extra-long railway tunnel projects in plateau areas. Therefore, it is necessary to analyze the difficulties, and influencing factors of construction ventilation in plateau areas, the advantages and disadvantages of different construction ventilation modes and their applicable conditions, as well as the control length of various ventilation methods.
Research conclusions: (1) For long-distance construction of high-altitude tunnels, priority should be given to tunnel-style ventilation. (2) When using pressure type single head ventilation, the recommended length of ventilation control for tunnel construction using drilling and blasting method is: when the altitude is less than 3 000 m, the length of single head ventilation should be controlled below 4.5 km; When 3 000 m < altitude ≤ 3 500 m, the length of single head ventilation should be controlled below 4.0 km; When 3 500 m < altitude ≤ 4 500 m, the length of single head ventilation should be controlled below 3.5 km. (3) When using air duct ventilation, economic and technical comparisons should be conducted based on factors such as required air volume, ventilation distance, and ventilation time to determine the size of the air duct section and the type of partition. (4) Concrete partitions should be used for long-distance air duct ventilation. (5) The results of this study can provide a reference for ventilation design of tunnel construction in plateau area.

Research purposes: The selection of tunnel portals in the alpine gorge region of the Qinghai-Tibet Plateau presents significant geological and environmental challenges. The tunnel entrance must also avoid geological disasters and flooding, select a stable location in the surrounding rock, and consider construction difficulty to reduce project risk and cost. This paper proposes quantitative evaluation indicators for the location of tunnel portals based on on-site geological surveys and UAV surveying and mapping. The proposed method combines a fuzzy comprehensive evaluation and modified grey clustering analysis to construct a comprehensive evaluation method. The purpose is to provide a scientific basis for the location of tunnel portals in this area.
Research conclusions: (1) An evaluation system is established based on factors such as lithology, slope, slope direction, elevation, distance from the ridge line, scale of the dangerous rock mass on the slope, distance from the fault, distance from the existing highway, and shortest distance from the corresponding position on the other side. (2) A comprehensive evaluation method for tunnel portal location is established by combining geological surveys, expert systems, and quantitative evaluation. (3) Compared to single methods, the evaluation method that considers fuzzy comprehensive evaluation and modified grey clustering analysis better reflects actual engineering characteristics and provides feasible suggestions for tunnel portal location. (4) The research results can be applied to the construction of mountain highway tunnels.

Research purposes: Urban railway is a rail transit system suitable for connecting the central urban area of a metropolitan area with surrounding urban clusters, providing public transportation, high-capacity, fast, and convenient transportation services. Therefore, some urban railway stations are built underground or on elevated railway lines in the city. The effective length of the station track is the main technical parameter for the design of railway stations, which directly affects the project investment and land resource utilization rate of railway construction. Based on the study of the effective length of arrival and departure lines of high-speed railway and intercity railways, combined with the characteristics of urban railways, this paper puts forward the scheme of shortening the effective length of arrival-departure tracks and the design scheme of the effective length of arrival-departure tracks for municipal railways on the premise of ensuring the traffic safety and considering the traffic efficiency.
Research conclusions: (1) The receiving route shall be set with a protection section. When the train stops at the station, the end of the protection section shall be used as the end of the train operation permit to improve the efficiency of parking at the station. (2) After the train arrives at the station and stops stably and accurately, the on-board equipment will withdraw the destination of the train operation permit to the exit annunciator, and report the information of stopping stably and accurately to the ground equipment. The ground equipment will automatically unlock the protection route, reduce the locking time of the protection section, and reduce the impact on other routes in the station. (3) This plan can shorten the effective length of the urban railway arrival and departure lines to 270 m, which is of great significance for reducing the scale of urban railway stations and lowering engineering investment, and can provide reference for similar projects.

Research purposes: With the development of intelligent technology, the intelligent construction technology of high-speed OCS engineering is becoming increasingly important. This study aims to systematically sort out the patent application trends, and regional and technological distribution characteristics in this field through comprehensive and in-depth patent analysis, analyze the research and development status of each technological branch, and explore its development laws and innovation directions, to provide a solid basis for promoting technological innovation and optimizing the industrial layout.
Research conclusions: (1) The patent applications for intelligent construction technology of high-speed OCS show an overall growth trend. It is in a stage of rapid development from 2015 to 2020 and has maintained a relatively high application volume since 2021, with a relatively high authorization rate and active innovation of the innovation entities. (2) China ranks first in the world in the number of patent applications in this field and is the country with the most patent layouts. Its technological level is leading, and its innovation ability and overall technological level are constantly improving. (3) The technology distribution is concentrated in mechanical equipment and professional tools, experimental simulation, and factory pre-configuration, among which the precise installation of mechanical equipment and professional tools and experimental simulation are the research hotspots. (4) The research results can be applied in the field of high-speed rail construction to improve the efficiency, quality, and safety of engineering construction and enhance China's international competitiveness and influence in the field of high-speed rail construction.

Research purposes: To rationally view the issue of low-volume rail transit, this paper proposes relevant suggestions for adjusting and optimizing the classification standards of urban rail transit in China. At the same time, sorting out the provisions of relevant domestic standards, norms, or policy documents, proposes an understanding of the concept of low-volume rail transit. Finally, several key points that should be paid attention to in the planning and construction process of low-volume rail transit in China were proposed for reference by colleagues in the rail transit industry.
Research conclusions: (1) Regarding the classification of urban rail transit, it is recommended to classify the system format in a "running form" and try to decouple it from factors such as transportation capacity, service level (within the same spatial range), right of way form, and design maximum speed, to avoid policy guidance from normative standards in vehicle selection. (2) There are many substitutes for low-volume rail transit, which is not a necessity, but just a possible choice. (3) The planning and construction of low-volume rail transit should attach importance to passenger flow prediction, compare cost-effectiveness with urban road public transportation, carefully choose the laying method, and improve urban management capabilities. (4) The results of this study can provide some reference for the classification of urban rail transit and the planning and construction of low-volume rail transit in China.

Research purposes: The side wall of subway station is usually constructed with composite steel formwork, the height of concrete pouring is 5~7 m, the vibrator needs 8~10 people, the vibrator labor intensity is bigger when concrete is poured, the working time at high altitude is longer, the quality of workers required high. In this paper, a kind of automatic vibrating equipment for side wall concrete is developed, which realizes the mechanization and intelligentization of vibrating of side wall concrete, improves the compactness of concrete, improves the construction quality of side wall and reduces workers, reduces the labor intensity, and improves the construction efficiency.
Research conclusions: (1) The application of automatic vibrating equipment reduces the number of workers from 10 to 3, thus reducing the safety risk. (2) The new-type insert magnetic vibrator can vibrate in all directions, effectively solve the instability of manual operation, avoid the common quality defects such as honeycomb and hemp surface, and ensure the quality of side wall concrete. (3) The compactness of concrete is improved, the construction quality is improved, the difficulty of defect treatment is reduced, and the cost of defect treatment is saved. (4) The automatic vibrating equipment can reduce each group of manual vibrating time from 10~12 hours to 6 hours, and improve the concrete pouring efficiency. (5) The equipment has been successfully applied to Qingdao Metro Line 5 project, filling the technical gap at home and abroad, and has a good application prospect.

Research purposes: With the expansion of track transit systems, traditional "manual inspection" methods face issues such as high labor costs, low efficiency, strong subjectivity, and easy oversights, making it difficult to meet the demands of track condition inspection. This study proposes a track inspection system based on the combination of two-dimensional grayscale images and three-dimensional data. Through the organic integration of high-precision mileage positioning technology and deep learning algorithms, intelligent and automated detection of common track defects is achieved, aiming to improve the efficiency and accuracy of track maintenance.
Research conclusions: (1) Combining three-dimensional imaging technology with two-dimensional imaging technology can effectively represent common appearance defects of track structural components such as rails, fasteners, and track beds. (2) An integrated mileage positioning method based on the combination of RFID and visual recognition technology can accurately locate the defects detected by the system, with a positioning error of less than 2 m/km. (3) Utilizing intelligent recognition methods centered on deep learning, combined with traditional historical data comparison algorithms, accurate detection of common defects in track structural components can be achieved through real-time processing of multi-dimensional visual data. (4) Through practical application, the system can significantly improve the work efficiency and detection accuracy of track inspection operations, providing practical value for guiding precise maintenance and achieving intelligent operation and maintenance.

Research purposes: The construction of railways in the Loess Plateau region, while promoting economic development, has significantly impacted land use and the fragile ecosystem of the area. By analyzing changes in landscape indices before and after the construction of Taiyuan-Zhongwei-Yinchuan Railway, this study aims to determine the key disturbance range along the railway and summarize the dynamic changes in land use types and ecological risks within the disturbance zone.
Research conclusions: (1) Significant changes in the landscape pattern were observed within 3 kilometers of the railway, particularly during the construction period, with patches becoming simpler and more concentrated, increased landscape fragmentation, and enhanced diversity. (2) Within the significant disturbance range, the intensity, speed, and extent of land use changes were substantial, with regional development intensity gradually increasing during both the construction and operation phases of the railway. (3) The Ecological Risk Index (ERI) within the significant disturbance range increased notably during the construction phase, with high-risk areas expanding rapidly; During the operation phase, ecological risks stabilized, but some high-risk areas persisted, indicating the long-term impact of railway construction and operation on the ecological environment. (4) The research results can provide scientific evidence for ecological protection in railway planning and construction in the Loess Plateau region, emphasizing the importance of balancing development and conservation.

Research purposes：In the process of China's high-quality economic development, the traffic network constantly promotes the optimization and upgrading of industrial structure by improving transportation efficiency, accelerating the flow of factors and enhancing regional economic ties. This paper focuses on the influence of traffic network density and R&D innovation investment represented by railways and highways on industrial structure upgrading, and puts forward targeted policy suggestions on this basis.
Research conclusions：(1) The space-time compression, economic agglomeration and knowledge spillover effects produced by the traffic network promote the advanced and rational development of industrial structure. (2) Increasing traffic network density and R&D innovation investment are important channels for upgrading industrial structure. (3) The effect of traffic network density on the upgrading of industrial structure is influenced by the development stage of industrial structure and the level of regional economic development. The construction of traffic network in the eastern region is conducive to the development of industrial structure to an advanced level, but it inhibits the rational upgrading. (4) The research conclusion can provide reference for further increasing traffic network density and R&D innovation investment, and promoting the development of industrial structure in the direction of upgrading and rationalization.

Research purposes: The construction of steel truss bridges in mountainous railway areas has had a significant impact on the regional environment due to complex terrain and fragile ecological environment. In order to reduce environmental impact from the source and improve its coordination with the environment, this paper evaluates the coupling coordination status between steel truss bridges and the environmental system based on the "CRITIC method-coupled coordination" model, and identifies the key influencing factors that affect the coordinated development of the system through the grey correlation degree model.
Research conclusions:(1)The mountainous railway steel truss bridge and environmental system were divided into overall and local bridge design, as well as 7 subsystems including water, atmosphere, geology, ecology, and acoustic environment. A "steel truss bridge-environment" system coupling and coordination index system was constructed.(2)The analysis of coupling coordination degree shows that the coordination state between the steel truss bridge and the environment is low-level coordination, and the key subsystems that affect the coordinated development are different in different periods. Moreover, the coordination degree fluctuates over time and needs to be optimized accordingly.(3)By identifying five key influencing factors, including the rationality of bridge site selection, bridge span, mechanical equipment exhaust emissions, bridge foundation selection, and bridge foundation cofferdam height, it can help optimize design and construction, reduce environmental damage, and protect regional ecology.(4)This research result can provide a scientific basis for the coordinated development of optimization and ecological protection in mountainous railway steel truss bridge engineering.