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: 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: The Jiujiawan landslide is a rare landslide geological disaster that caused damage and suspension of high-speed railway since the construction of high-speed railway in China, and it will surely have a far-reaching impact on the geological alignment selection in the construction of high-speed railway. The study of the characteristics and causes of this landslide will help the technical workers have a deep understanding of the high slopes along the high-speed railway and their potential risks, and provide valuable experience for the prevention and control of similar geological disasters in the future.
Research conclusions: (1) Jiujiawan landslide is a new landslide formed by the instability of natural slope, and it is a natural disaster that occurs suddenly under the combined effect of extreme heavy rainfall and man-made activities on high steep slopes of mudstone sandwiched with gypsum rock. (2) The long-term leakage of the irrigation canal at the foot of the slope is the main reason why the landslide was able to continue to slide forward on the river terrace for three days and travel more than a hundred meters after being sheared out from the foot of the slope and ultimately caused damages to the bridges of Lanzhou-Xinjiang High-speed Railway. (3) The research results can be applied to the selection of railway schemes in mountainous areas to avoid the risk of the line being subjected to landslides and geological hazards.

Research purposes: Ventilation system is very important in the disaster prevention and rescue system of railway tunnels, and ventilation standards significantly affect the safety and investment of rail project. The effects of smoke concentration control and project economy at different wind speeds cases on a typical emergency rescue station between continuous tunnel portals were calculated, and the results can help to renew the ventilation standards.
Research conclusions: (1) The distribution of smoke concentration along the passenger evacuation route is influenced by multiple coupled factors, including the location of the fire source, valley winds, and the wind speed inside the tunnel. (2) When the burning train carriage is 10 meters away from the tunnel portal and there is a valley wind of 5 m/s, a tunnel wind speed of 0.5 m/s can ensure that the intrusion of smoke into the tunnel does not exceed 20 meters. (3) The wind speed standard has obvious influence on the fan configuration of disaster prevention ventilation system, and lowering the wind speed standard to 0.5 ~1.0 m/s can reduce the total number of fans by 1/3~1/2 compared to the current regulatory standards. (4) Considering safety and cost factors, it is suggested to reduce the wind speed standard to 0.5 ~1.0 m/s . (5) The research results can provide reference for the formulation of ventilation standards and ventilation system design of emergency rescue station between continuous tunnel portals。

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: The Quaternary cover layer in the Chengdu area is thick, overlying the red soft rock strata, with a variety of rock and soil types. The unique geological environment has given rise to numerous geotechnical engineering problems, which have constrained the planning and construction of Chengdu rail transit. Through a series of geotechnical engineering practices in Chengdu rail transit construction, this paper systematically analyzes the geological characteristics and causes of various problems and proposes targeted geotechnical investigations of key points and corresponding prevention and control measures.
Research conclusions: (1) The Chengdu rail transit is mainly located in the central part of the Sichuan Basin, which belongs to the Minjiang River watershed. Its geological structures are mainly box-shaped Longquan Mountain anticline, and the basic seismic intensity is Grade Ⅶ. (2) The Chengdu Plain is widely distributed with thick Quaternary Holocene System (Q₄) and Pleistocene System (Q₃) clay, pebbles, and sand layers, while the cover layers on the hilly and low mountain areas are thinner. The underlying bedrock is the Cretaceous System (K) and Jurassic System (J) red lacustrine sedimentary mudstone, sandstone, etc., with thin layers of gypsum and calcareous halite commonly found in the mudstone. (3) The study area has diverse rock and soil types, and the Chengdu rail transit construction faces large-grained high-strength floating pebbles, lenticular sand layers, Ya'an gravel layers, gypsum-containing formations, shallow gas, red mudstone, composite formations, and hydrogeological problems. The paper provides a detailed explanation of the engineering geological characteristics, geotechnical investigations key points, and control measures for each problem. (4) The research results have reference and guidance significance for the construction of the fifth phase of the Chengdu rail transit and the second phase of the Chengdu suburban railway network.

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: 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: To accurately reflect the differences in lateral resistance provided by layered rock-soil foundations to pile foundations, as well as the elastic support effect of prestressed anchor cables, considering the issues in the calculation of multi-row prestressed anchor cable piles and the limitation of existing finite difference methods (FDM), a model considering both loading segment and anchoring segment for prestressed anchor piles was developed based on the Euler-Bernoulli beam method. The internal force and deformation of the entire pile were solved using the discretization of the pile shaft and an improved finite difference approach. The calculation program developed by the programming language could improve the efficiency and accuracy of anchor pile design.
Research conclusions: (1) A model considering both the loading segment and anchoring segment for prestressed anchor cable piles is developed, which could provide an accurate prediction of the internal force and deformation of the entire pile embedded in layered foundations. (2) Matrix-based linear equations are proposed for solving the pile deformation by adopting a central difference scheme, which provides a more simplified analysis process compared with existing finite difference methods. (3) The FDM operation and graphics program is developed with Python language. In comparison to the engineering case and numerical simulation, it indicates that the proposed method was reasonable for evaluating the anchor cable piles embedded in multi-layered soils and rocks. (4) The design software for prestressed anchor cable piles has been successfully applied to the design and verification of anti-sliding piles, which has achieved good application results in railway slope protection.

Research purposes: The suburban railway is an important mode of transportation to realize the integration of urban and rural areas, and its planning and construction are being vigorously promoted. However, at present, the interconnection relationship between suburban railways and various levels of rail transit is mostly analyzed at a single node, without stratified research from the perspective of the network level. Therefore, guided by the relevant planning of Shanghai and based on the passenger flow, based on the basic network pattern of Shanghai rail transit, this paper studies the interconnection relationship between Shanghai regional railway and national railway, near Shanghai regional line and municipal network from a hierarchical perspective, in order to provide a criterion for the interconnection relationship of Shanghai suburban railway.
Research conclusions: (1) With the national railway trunk line, it is recommended that the Shanghai airport link line, the East-west link line and the national railway cross-line operation. (2) Based on the planning guidance and the form of ring + ray, it is proposed that the ray should be operated across the line with the near Shanghai regional railway, and the transfer form can be adopted between the ray and the ring line. (3) In Shanghai, the suburban line network is mostly distributed in a chessboard shape. The vertical and horizontal lines and the suburban line extending into the main urban area should be operated across the line. The horizontal line and the vertical line should be comprehensively compared and selected for passenger flow, travel time, engineering investment and other factors. Under the condition that it does not have a great impact on the line station plan, it is suggested that the horizontal line and the vertical line should be operated across the line, and the ' L ' line should be used to make up for the parallel line defects, and the internal layout is equivalent to the radial line. (4) The research results can provide a reference for the selection of suburban railway interconnection relationship.

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: 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 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: Foreign object intrusion is one of the most serious threats faced by railways, and in recent years, train derailments and casualties have occurred repeatedly. At present, foreign object intrusion mainly relies on personnel monitoring, but personnel cannot monitor and warn in real time, and there are many blind spots. In order to achieve real-time intelligent monitoring of foreign object intrusion, the monitoring technology of U-Net siamese network model was studied, and sample libraries of different types of foreign objects were established. By comparing and analyzing with traditional methods, the effectiveness of our method was verified, laying the foundation for the engineering application.
Research conclusions: (1) The proposed U-Net siamese network model constructed by ResNet-101 integrates semantic information of different scales, greatly reducing the problem of missed detection of target objects, and has obvious advantages compared to traditional algorithms. (2) The U-Net siamese network model has generalization ability in recognizing different types of foreign objects, with high recognition rates for trains, personnel, tree branches, stones, and light floating objects. (3) The accuracy and recall of U-Net siamese network model reached 0.95 and 0.96, respectively, with false detection and missed detection rates of 0.05 and 0.04, meeting the requirements of railway monitoring. (4) The research results can provide a scientific method for intelligent recognition of railway foreign object intrusion, which can serve as an important supplement to manual inspection and has great promotion value.

Research purposes: During the construction of railway karst tunnels, when problems such as water gushing, mud bursting, and huge cavities are encountered, the design changes will be carried out based on supplementary investigation, and the operation safety can generally be guaranteed after renovation. However, some karst hydrogeological problems of railway tunnels that are not exposed during the construction period may form diseases that affect the operation's safety under extreme rainfall and other conditions after opening for operation. Hydrogeological diseases during the operation of typical railway karst tunnels mainly include track uplift, sidewall damage, mud gushing and sand gushing, and large water inflow. It is necessary to summarize these diseases in the operation period and analyze their causes, to provide a reference for avoiding similar diseases in the railway operation period.
Research conclusions: (1) The construction excavation blocking the underground river channel at the bottom of the tunnel reduces the drainage capacity of karst water. After extreme heavy rainfall, the inflow of water on the upstream side increases, which can lead to an increase in groundwater level and thus increase the water pressure acting on the bottom of the tunnel. When the bottom of the tunnel cannot resist the action of water pressure, a rail lift may occur. (2) During the operation stage, the reasons for the cracks on the side wall of the tunnel are mostly related to the open karst caves on the side wall. The lack of understanding of the rapid rise of karst water pressure in the cavity around the tunnel under extreme rainstorms and the lack of targeted water diversion and drainage measures may lead to cracks in the secondary lining after extreme rainfall. (3) During the operation of the tunnel, there is a surge of mud and sand. Due to heavy rainfall, the groundwater level around the tunnel rises and the water pressure increases, causing the mud and sand in the surrounding dissolution joints and grooves to be "pressed" into the tunnel. When mud and sand surges occur during construction and operation, the treatment measures should mainly focus on diversion and drainage. (4) The necessity of adding a drainage tunnel during the construction process should be fully considered, taking into account the water inflow situation under extreme weather conditions and the operational interference caused by a large amount of water inflow. (5) The research results of the paper have reference value for guiding the survey and design of tunnel engineering in karst water development 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: 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: With the continuous increase in the operating speed of urban rail transit, the performance of the existing rigid catenary system under high-speed conditions of 250 km/h has not been fully studied. To meet the growing demand for passenger flow and ensure the stability and reliability of high-speed train operations, it is imperative to optimize the design of the rigid catenary system for 250 km/h speeds. This paper aims to use the finite element simulation method, investigate the influence of different structural parameters on the dynamic performance of the pantograph-catenary system, and propose a design scheme for the rigid catenary system suitable for 250 km/h speeds, providing theoretical support and engineering guidance for the power supply system of high-speed urban rail transit.
Research conclusions: (1) Through simulation analysis, the basic structural parameters of the rigid catenary at 250 km/h speed were determined: a span of 6.5 m, anchor stiffness of 68 600 N/m, and a 200% increase in the longitudinal moment of inertia of the busbar can significantly improve the dynamic performance of the pantograph-catenary system. (2) The transition structure parameters were optimized: the anchor stiffness of the fracture-type anchor section joint was set to 200 000 N/m with a span of 2 m, and the anchor stiffness of the through-type anchor section joint was set to 200 000 N/m with a span of 4.5 m. Reducing the weight of expansion elements appropriately can effectively enhance the dynamic performance of the anchor section joint. (3) By extending the length of the rigid-flexible transition busbar to 5.4 m and adopting gradient-varying anchor stiffness, the contact force requirements for the pantograph passing through the rigid-flexible transition section at 250 km/h can be met. (4) The influence of geometric deviations at the anchor section joint on the contact force was studied, and it is recommended to control the geometric deviation within ≤5 mm to ensure the stability of the pantograph-catenary contact performance. (5) The research results of this paper can provide a theoretical basis for the design of rigid catenary systems at 250 km/h and higher speeds, applicable to the optimization of power supply systems in high-speed urban rail transit, underground railways, and other related fields.

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: With the continuous improvement and rapid construction of China's railway network, the impact of railway engineering on the ecological environment along the routes has become increasingly evident. Particularly in ecologically fragile desert regions, the issue of environmental pollution during railway construction is more pronounced. Although green construction practices have been widely adopted in railway development, there is still a lack of systematic environmental impact assessment frameworks and methodologies, making it difficult to accurately evaluate the actual environmental impact of construction activities and to provide a scientific basis for environmental management decisions. In light of this, this paper aims to establish a scientifically sound environmental pollution evaluation index system for green railway construction in desert areas, comprehensively reflecting the impact of construction activities on water environment, atmospheric environment, acoustic environment, solid waste disposal, and ecosystems. Furthermore, it seeks to develop a quantitative environmental impact assessment model to achieve an objective evaluation of the environmental impact of green railway construction. Lastly, through empirical research, the paper intends to validate the effectiveness of the evaluation system, providing theoretical support and practical guidance for formulating targeted environmental protection measures.
Research conclusions: (1) This paper constructs an environmental pollution evaluation index system for desert railway green construction, comprising 5 first-level indicators and 16 second-level indicators. It innovatively combines the entropy weight method with the fuzzy comprehensive evaluation method to establish a quantitative environmental impact assessment model. Using this model, the paper evaluates the environmental pollution impact of green construction on a section of the Golmud-Korla Railway. The environmental pollution evaluation grade for this section is "weak", indicating a relatively minor environmental impact. (2) Ecological disruption is the primary factor causing environmental pollution in railway green construction, and protective measures should be implemented during construction to effectively control it. (3) This evaluation index system can provide a direction for further improvement in the prevention and control of environmental pollution in railway green construction, offering reference value for optimizing construction measures and improving pollution management methods. It holds reference value for reducing environmental pollution and achieving high-quality green railway construction.

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: 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: To explore the factors affecting the dynamic coefficient of large-span through type railway arch bridges, a representative 430 m main span through type steel tube concrete arch bridge in China was taken as the research object. A large multi-body dynamic analysis software ADAMS/RAIL was used to establish a simulation analysis model of the car rail bridge. Based on the characteristics of vehicle-induced vibration of large-span railway arch bridges, the vehicle bridge coupling analysis method was used to investigate the effects of different types of suspension rods, train types, track irregularities, running speeds, and other operational factors on the dynamic coefficient of suspension rod cables.
Research conclusions: (1)Using the dynamic coefficient of the suspension rod cable is more reasonable than studying the dynamic coefficient of deflection. (2)The influence of vehicle speed on the dynamic coefficient of suspension cables varies at different positions on the bridge span. Suspension cables with higher dynamic coefficients are mainly located at and near 1/4 of the bridge span, which is related to the lower vertical stiffness of the bridge near this location. When the vehicle speed exceeds 300 km/h, the power coefficient of the suspension rod increases significantly, reaching a maximum of 1.62. Due to the sudden increase in the dynamic coefficient, if using cable suspension rods, a high fatigue amplitude anchoring system should be adopted to ensure their reliability. (3)The unevenness of the track has little effect on the dynamic coefficient of the suspension rods at various positions of the bridge span. (4)The difference in dynamic coefficient response between steel cables and carbon fiber cable suspension rods is not significant. (5)The trend of changes in the power coefficient of freight cars is smoother than that of high-speed trains, and high-speed trains have a greater impact on bridge spans than freight cars. (6) The findings of this study can serve as a reference for the design and calculation of dynamic coefficients for similar large-span railway arch bridges.

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: With the rapid development of railway transportation and the acceleration of nationwide urbanization, railway freight stations, as core infrastructure of the transportation and logistics system, play a crucial role in reducing overall logistics costs. This paper addresses current challenges faced by railway freight stations, such as outdated facilities, industrial mismatches, and limited urban integration, and explores new pathways for their transformation into modern logistics hubs while promoting integrated development with cities and industries. The findings are expected to contribute to the high-quality development of China’s railway freight sector.
Research conclusions: (1) The theory of "Station-Industry-City" integrated development is innovatively proposed, with railway freight stations as the core, included its development connotation, path, and stages. (2) The integrated development strategy of "Station-Industry-City" is summarized from five dimensions: functional integration, transportation integration, industrial integration, spatial integration, and data integration. (3) The effectiveness of the theory is validated through an empirical analysis of the Chongqing Tuanjie Village Container Center Station. (4) The research results can provide theoretical guidance and practical references for the planning and design of new large-scale railway freight stations and logistics bases, as well as the renovation of existing freight facilities.

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 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: 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: With the development of underground space utilization and underground rail transit, it is common to encounter deep excavations in urban areas that are adjacent to or underpass existing railways and other critical structures. However, a systematic understanding of related construction technologies remains lacking. Based on a highway underpass railway overpass project in Wenzhou, this study focuses on the construction safety of deep excavations close to railway overpasses, aiming to develop a scientific methodology for low-disturbance construction of deep excavation projects under existing railway lines.
Research conclusions: (1) A reliable support scheme of "double-row piles + steel/concrete internal bracing" was proposed, and a refined, whole-process numerical model for deep excavation adjacent to railway overpasses was established. (2) Based on this model, the deformation characteristics and stability of the excavation and bridge piers during the excavation process were systematically studied, and the "deflection effect" of pier inclination was proposed according to the displacement characteristics. (3) The validity of the numerical model was confirmed by comparison with monitoring results, and a technical scheme for "low disturbance and rapid construction" of deep excavation adjacent to important buildings was summarized. (4) The research findings can provide a reference for the design of deep excavations close to railway overpasses.

Research purposes: Faced with the new situation and requirements of the urgent need for renovation and reconstruction of a large number of old railway passenger stations and surrounding urban areas in our country, Xi'an Railway Station has also presented the reality problem of the disconnection between "station" and "city" and the coordination between "ancient" and "present".This paper focuses on the renovation of the Xi'an Railway Station hub area from the perspective of urban renewal, summarizing issues such as transportation network structure, urban functional formats, and cultural landscape, and proposes a renewal method for the old railway station area by combining station-city integration and catalyst renewal strategies.
Research conclusions: (1) The research method is proposed combining catalyst renewal theory and station-city integration theory to address the complex situation of updating and renovating old railway stations. (2) The urban renewal strategy is proposed for old railway stations in the hub area of Xi'an Railway Station, which integrates urban functions, transportation functions, landscape functions, and cultural features. (3) The overall research direction of "pre planning and post evaluation" is proposed for the updating and renovation of old railway station areas. The paper explores the practical solution of "integrating hub transportation and urban functional space, focusing on the inheritance and expression of cultural heritage with large heritage sites" for the stock renewal of hub areas.

Research purposes: The Xijiang Super Major Bridge of Zhuhai-Zhaoqing High-speed Railway is a cable-stayed bridge with three towers and a main span of 2×435 m. To reduce the bending moment of the middle tower, reinforcing cables have been set up between the top of the middle tower and the side tower. To reduce the diameter of the reinforcing cables and consider its replaceability, the reinforcing cables is in the form of parallel double cables. Based on the experimental results of the aerodynamic characteristics of the downstream cylinder in the double cylinder system, the study and analysis of the characteristics of wake-induced vibration of the downstream strengthened cable under wind action in different inflow directions are carried out through numerical calculation methods, and appropriate vibration suppression measures are proposed.
Research conclusions: (1) Numerical calculation method was used to analyze the wake-induced vibration of parallel reinforced cables with a spacing ratio of L/D=3.17 (L is the distance between the center of the reinforced cable and D is the cable diameter). When the central connecting line between parallel cables is at a certain angle to the incoming flow direction, the wake-induced vibration along a circular trajectory will be caused for the uneven spatial distribution of the aerodynamic force of the downstream cable. (2) Within the range of 1.5% damping ratio, simply increasing the damping ratio of the cable cannot suppress the occurrence of wake-induced vibration, and has limited effect on reducing the amplitude of wake-induced vibration. By setting auxiliary cables and transverse connecting rods to increase the stiffness or natural frequency of the cables, the occurrence of wake-induced vibration can be effectively suppressed. (3) This study can provide reference and inspiration for the design of cable-stayed bridges using double row cable-stayed or reinforced cable.

Research purposes: The traveling safety and system vibration assessment when the train crosses a large-span flexible bridge are the key technical difficulties in the design and construction of high-speed railway bridges toward large-span and high-flexibility, and the coupled dynamics analysis of train-track-bridge is the core. Considering the longitudinal large-scale nature of large-span bridges, the overall modeling of the track structure on the bridge will bring inefficiency in modeling and computational efficiency, which makes it difficult to meet engineering needs. In this paper, based on the classical coupled vibration theory of train-track-bridge, the cyclic calculation method and substructure power iteration method are introduced to realize the coupled train-track-large-span bridge vibration analysis by moving the truncated train-track subsystem on the bridge, as well as coupling the time-varying matrix with the bridge subsystem and solving the power iteration. Numerical analysis is carried out for two key parameters in the computational model: the track truncation length and the substructure integration step.
Research conclusions: (1) When analyzing the vibration of the large-span bridge, it is recommended that the track truncation length of more than 200 m. (2) In order to take into account the high-frequency vibration of the train-track system and the efficient calculation requirements of the bridge system, it is recommended that the integration step of the train-track system is 0.000 5 s, and the bridge system integral step is 0.001 s. (3) Based on the calculation model proposed in this article, the reasonable range of values for the longitudinal section parameters of the herringbone slope of long-span bridges is studied. When the slope ≤12 ‰ and the vertical curve radius R≥20 000 m, the longitudinal section setting requirements in the specifications are met. (4) The coupled vibration analysis method proposed in this paper realizes efficient modeling and efficient calculation, which can provide theoretical and technical support for the longitudinal section research of kilometer-class large-span bridges.

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: Focusing on an under-construction underground high-speed railway (HSR) line and a subway line that cross perpendicularly in close proximity to a large underground commercial space, this study established a train-track coupling analytical model and a three-dimensional finite element model of the underground structure-soil system to determine the vibration response. Considering various speed combinations of the HSR and subway trains, this study analyzed the propagation laws of vibrations caused simultaneously by their operation within the underground space and on the ground surface. The vibration isolation effect of underground space on the HSR is also investigated. The findings provide critical references for vibration impact assessment and mitigation design of high-speed railways and subways.
Research conclusions: (1) Vibration amplification effect occurs on both sides of the tunnel as high-speed railway or subway trains travel. For the subway station and underground space with the same burial depth, periodic vibration amplification zones occur on the ground surface, and the vibration response of the surface is greater than that of the underground space. (2) The train speed and distance between the receiver point and track have a significant impact on the growth rate of Z-vibration level on the ground surface and in the underground space. The speed increase of high-speed trains has a relatively small influence on the growth of Z-vibration level, while that of subway trains has a greater impact. Moreover, the speed increase of subway trains leads to a more significant amplification effect of surface vibration. (3) The underground space can be regarded as a transmission path vibration reduction measure. For the 250 km/h high-speed train passing under the underground space and 60 km/h subway train passing beside the underground space, the underground space can reduce Z-vibration level on the ground surface by 5.0~9.2 dB and 0.6~4.5 dB, respectively.

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: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: 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: 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: 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: The relative accuracy of the whole length of the traverse and the azimuth closure difference are the main indicators to evaluate the accuracy of the traverse, because the plane control network of the long tunnel is usually measured in the form of the traverse network, which leads to the problem that the path and accuracy of the dominant line are not unique, and how to choose the optimal connecting traverse path is of great significance to the evaluation of the accuracy of the traverse.
Research conclusions: (1) The results of the mainstream traverse network adjustment software Cosa and SYADJ are not unique in the calculation of the main path of the long tunnel traverse network. (2) The optimal path algorithm proposed in this paper is not affected by the order of the adjustment file in the path selection process, and the dominant line result is unique, with higher accuracy and better stability. (3) In the evaluation of tunnel traverse accuracy index, the principle of determining the dominant line should be improved to avoid contradictory calculation results of different software of the same plane control network. (4) Combined with the data processing experience of the long tunnel traverse network, the research results of this paper put forward suggestions for the accuracy evaluation of the long tunnel traverse network, which is suitable for the calculation of the plane control network of the long tunnel.