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 large area goaf is one of the important factors to control the route scheme of railway engineering. Currently, the boundary angle is adopted for the railway with special protection grade when calculating the safe distance from goaf, and the moving angle is adopted for railways with other protection grades. However, it is difficult to meet the deformation control requirements of railway lines by using the moving angle calculation for some protection grades. In this paper, starting from the difference between the three critical deformation values of curvature, inclination and horizontal deformation included in the moving angle and the requirements of railway deformation control, the angle formed by the horizontal line on the side of the pillar and the line connecting the outermost point determined by curvature and inclination to the boundary of the goaf is defined as the curvature-tilt angle. Based on the basic theory of probability integral method of moving basin in goaf, the relationship between curvature-tilt angle and critical strata displacement angle is systematically analyzed by means of theoretical analysis, program development, mathematical statistics and case verification. The range of critical strata displacement angle under different railway grades and different rock strata conditions is studied and proposed.
Research conclusions: (1) There is a significant linear correlation between the critical strata displacement angle and the curvature-tilt angle. The movement angle is close to the curvature-tilt angle and the movement angle is not greater than the curvature-tilt angle. The curvature-tilt angle can be used as the intermediate bridge to establish the conversion relationship between the movement angle and the critical strata displacement angle.(2) When the type of overlying rock in goaf is hard rock, relatively hard rock, relatively soft rock to extremely soft rock, the critical strata displacement angle is about 7°, 4°, 3°smaller than the movement angle respectively.(3) Verified by the measured data of multiple goafs, the proposed value ranges of the critical strata displacement angle are in agreement with the measured data, which can provide reference for the calculation of the safety distance between railway and large-area goafs.

Research purposes: Disturbed in-situ stress caused by construction has an important impact on the risk of rock burst in parallel deep-buried tunnels, and may lead to delayed rock burst in the preceding tunnel. However, the existing research is difficult to meet the needs of assessing the scope of the disturbed in-situ stress zone during railway tunnel construction, which in turn makes it difficult to satisfy the requirements for the refined design of the clear distance between two parallel single-track railway tunnels. Based on the comprehensive analysis and comparison of measured in-situ stress data in tunnels, the main law and depth range of the disturbed in-situ stress in the Qinling natural rock mass are determined.
Research conclusions: (1) According to the characteristics of the disturbed in-situ stress-depth curve, natural hard rock mass can be divided into two end-element models, namely, the homogeneous rock mass model without structural plane and the relatively homogeneous rock mass model with structural plane. (2) The measured in-situ stress of hard rock in Qinling area is mostly close to the model with structural plane, and the depth of disturbed in-situ stress zone is 18~25 m; a few cases can be considered as the mode without structural plane, with a depth of 7~10 m.(3)The disturbed in-situ stress zone of Class II and III surrounding rock can be considered as 10 m and 25 m, respectively. Therefore, it suggests that the clear distance between two parallel single-track high-grade railway tunnels should reserve a sufficient safety value according to this rule. (4) This achievement can be applied to the geological route selection of railways and highway in Qinling and similar mountainous areas and to the prevention and control of rock burst risk in tunnels.

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: The planar alignment serves as the core element of turnout design and plays a vital role in ensuring smooth and safe train operation. Currently, China's high-speed electromagnetic suspension (EMS) maglev transportation technology has entered a critical phase of engineering application, making it imperative to systematically master turnout design methodologies and conduct targeted optimizations. This paper comprehensively summarizes the design requirements for planar alignment in high-speed maglev turnouts. A systematic approach for alignment design and parameter calculation adaptable to varying operational speeds is proposed, along with an investigation into the key factors influencing turnout length. The research outcomes provide essential technical support for the independent development and iterative optimization of high-speed maglev turnout systems in China.
Research conclusions: (1) To shorten the length of high-speed maglev turnouts, the adoption of clothoid transition curves is recommended.(2) Constrained by the vehicle's structural radius, even when the turnout's lateral passing speed is extremely low, the length of existing flexible and bendable high-speed maglev turnouts can hardly be reduced below 50 m. (3) For turnouts with lateral passing speeds below 50 km/h, a single circular curve alignment is suggested, eliminating the need for transition curves. (4) When engineering constraints prevent the simultaneous adoption of extreme values for both maximum unbalanced centrifugal acceleration and its increment, priority should be given to increasing the unbalanced acceleration tolerance,i.e., enlarging the circular curve radius from the perspective of minimizing turnout length. (5) Implementing a narrow-body vehicle design can reduce the end offset distance of the bendable turnout section, theoretically shortening the turnout length by 8%~11% compared to existing designs. （6）The results of this study can guide the plane linear design of high-speed maglev turnouts.

Research purposes: The rack railway has become the predominant structural type for mountain rail transportation because of the advantage of strong climbing ability. To guide the track selection for a specific rack railway in Southwestern Mountainous Regions, this paper outlines the project engineering overview and proposes the track structure requirements and selection principles, through the analysis of rack railway transportation application status and engineering characteristics worldwide, the track structure type and design scheme suitable for rack railway were proposed from the aspects of rack rail system, track type, rail and rack rail, fastening system, sleeper structure, turnout system,and transition device.
Research conclusions: (1)Because of its superior installation convenience and lower maintenance costs, the Strub rack system was recommended. (2) Ballasted track requires lower engineering investment,adapts better to various curves and geological conditions, and has wider engineering applications. Ballasted track structure is recommended, but ground anchors and tie anchors should be installed as anchoring measures. (3) Continuous welded rail could ensure operational stability, and reduce the maintenance workload, the 50 kg/m continuous welded rail is recommended, and the rack should be optimized design based on the rail, employing a continuously welded structure. (4) Considering the adaptability of rack system, reliability of turnout structure, and line operation efficiency, it is recommended to prioritize the use of covered separable rack rail turnouts and a three-stage buffered gear mechanism. The translational type rack rail turnout offers excellent operational stability and strong adaptability, it can be adopted where space is sufficient. (5) The research results can provide a reference for track structural selection and design of mountain rack railway.

Research purposes: To study the static performance, force transmission mechanism and ultimate bearing capacity of the external cable girder steel anchor box used in the new bridge across the Yongjiang River,a 1∶2 scaled static test model was designed based on the actual bridge's stress state, the stress state and force transmission process of the test model and the original bridge were analyzed according to the finite element calculation and test results, so as to check whether the static performance of the test model meets the design requirements, and verify the rationality of the finite element calculation model. According to the analysis of the axial load displacement of the test, the ultimate bearing capacity of the steel anchor box of the external cable girder was studied.
Research conclusions: (1) The results show that the external cable girder steel anchor box mainly transmits the cable force in the form of shear stress through the connection weld between the anchor box body and the main beam web, and mainly relies on the three welds to transmit the cable force,accounting for 94.59% of the total cable force.(2)The stress distribution of the plate parts of the cable girder steel anchor box is relatively uniform, but the stress concentration phenomenon of the main plates is obvious, and the stress concentration problem near the connecting weld between the main beam web and the supporting plate is significant, which should be paid attention to in the design.(3)The stress values of the static test points maintain a linear relationship during the loading process, the structure is in an elastic working state, the test values are in good agreement with the finite element calculation results, verifying the correctness of the simulation results, and there is an obvious stress concentration phenomenon in the test model.(4)In the process of ultimate bearing capacity loading, due to the large eccentric load of the external anchor box, the bottom anchor structure could no longer sustain the load, and the final load is 5 400 kN, which is about 2.2 times of the design load.(5)At the same time, the bearing capacity of the original bridge model was analyzed by finite element calculation, and the ultimate bearing capacity of the original bridge cable girder structure was obtained to reach 8.5 times of the design cable force. The research results provide a reference for the safe use and structural design of the external cable girder steel anchor box.

Research purposes: Separated double composite beams are widely used in bridge engineering due to their simple structure and superior mechanical properties. However, its passivation section is prone to vortex-induced vibration (VIV), which is more significant at large wind attack angle. The VIV performance of the section was tested by the sectional model wind tunnel test of 1/45 scale. The influence of damping ratio and the cause of VIV were discussed. Furthermore, single and combined aerodynamic measures such as closed double girder openings, segmented closed outer handrails, and three types of deflectors were proposed and tested.
Research conclusions: (1) The separated double composite beam experiences significant vertical VIV at 0°, -3°, ±5° and ±7° wind attack angles, and the amplitude increases with the increase of the attack angle.(2) Reducing the damping ratio can increase the amplitude of vertical VIV and excite torsional VIV. The damping ratio within the range of 0.3% to 1.0% has a greater impact on vertical VIV than torsional VIV.(3) The segmented closed outer handrails can control the VIV response at +5° and +7° wind attack angles, and the guiding plates can control the VIV response at 0° and -3° wind attack angles.(4) The combined aerodynamic measures integrate the advantages of the two measures, and the control efficiency at -5° wind attack angle has reached 81%, but the control at -7° wind attack angle is limited.(5) The results of this study can provide reference and guidance for optimizing aerodynamic measures for VIV of separated double composite beams at high angles of attack.

Research purposes: The cast-in-place pile of bridge and bridge rescue channel on the rock stratum and soil stratum of a high-speed railway under construction was detected for its integrity by the reflection wave method, it is found that some piles have obvious and serious defects, such as excessive grout and honeycomb holes at pile top, necking at both shallow and deep sections of the pile, insufficient pile length and thick silt at pile bottom, etc., and both the construction and rework processes cause serious waste of funds; therefore, the reasons are analyzed, and the special measures to improve the construction quality of bridge cast-in-place pile are studied in this paper, so as to effectively improve the integrity of pile body, strictly control the waste and save funds.
Research conclusions: (1) At the macro level, attention should be paid to the matching of pile type and stratum conditions. In limestone strata, slurry wall protection measures should be strengthened, and the concrete slump should be strictly controlled within the range of 180~220 mm.(2) At the micro level, specialized control measures should be implemented for different parts of the cast-in-place pile: the concrete height over-poured at the top of the pile shall be 1.5 to 2.0 m and 2.0 to 3.0 m respectively at the design elevation of the pile top for piles with a diameter of 1.0 m and 2.0 m; the shallow part of the pile shaft in unstable strata within the groundwater fluctuation zone should use long permanent casing for wall protection to prevent hole collapse and the resulting hole enlargement or shrinkage; the construction of holes in the stable soft plastic silt layer and unstable soft plastic sand layer at the depth of the pile requires the use of bentonite, cellulose, and mud with a weight of 1.3 to protect the wall; the bottom of the borehole shall be carefully measured for depth and the properties of the mud shall meet the required standards for cleaning, the allowable thickness for the rock-socketed pile is 50 mm and 200 mm for friction pile, and the thickness of the sediment is zero after the bottom is sealed by the counter-flushing action of the initial concrete pour.(3) The implementation of special measures has effectively improved the integrity of the pile body, strictly controlled waste, saved funds, met the design requirements, and achieved a proportion Class I and Class II qualified piles in one construction exceeded 99.5% and fell below 0.5% of the total pile count, respectively, and the number of Class II piles in the same pier does not exceed 1, achieving a saving of more than 2 million yuan and more than 20 million yuan for a contract section and the entire railway construction, respectively.(4) The research results can provide reference for implementing special measures in rock and soil layers to improve the construction quality of bridge cast-in-place piles in fields such as railways and highways.

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: 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: The existing power supply detection and monitoring systems have not been included in the scope of energy efficiency management, and there is a lack of systematic collaborative architecture design for energy efficiency improvement and power supply safety. This study with the aim to achieve efficient and safe operation of railway power supply systems, clarifies the safety and energy efficiency requirements of railway power supply systems, constructs a multi-dimensional integrated technical system, and conducts in-depth research on key technologies and collaborative methods for power supply safety and energy efficiency improvement, providing theoretical support and practical guidance for improving the reliability and economy of railway power supply systems.
Research conclusions: (1) A railway power supply safety and energy efficiency improvement system architecture has been constructed. In terms of power supply safety, a catenary online monitoring technology based on the Internet of Things and sensor technology is proposed, which can monitor the status of key equipment such as wires and tension compensation devices in real time. At the same time, a station auxiliary monitoring system including video monitoring, environmental monitoring and other subsystems is built to improve equipment fault warning capabilities.(2) In terms of energy efficiency improvement, a renewable energy utilization scheme of "bidirectional energy integration + energy storage+10 kV grid connected feeding" has been formed, using a hybrid energy storage system of super capacitors and chemical batteries to optimize energy recovery. A multi technology integrated station energy management system has also been designed to achieve refined energy consumption management.(3) Establishing a collaborative architecture with security assurance layer, energy efficiency improvement layer, etc., and maximizing energy efficiency under safety priority through cost function and dynamic energy allocation model, the research results can effectively support the engineering practice of railway power supply safety and energy efficiency improvement, which is of great significance for promoting the high-quality development of railway power supply system.

Research purposes: To meet the demand for increasing the operating speed of urban rail transit to 250 km/h, the existing rigid catenary systems lack suitable design solutions. To ensure stable pantograph-catenary current collection, safe and reliable operation of high-speed trains at 250 km/h, it is crucial to determine the key design parameters of the transition structure in high-speed rigid catenary systems. This study establishes a pantograph-catenary dynamic simulation model based on the finite element method, tailored for 250 km/h operation. Using the control variable method, this paper systematically investigates the influence of rigid catenary transition structure parameters on system dynamic performance. Through simulation modeling and parameter analysis, key parameters of the mid-span overlap and rigid-flexible transition structures in the rigid catenary are optimized, providing theoretical support for the engineering design of high-speed rigid catenary systems.
Research conclusions: (1) For discontinuous mid-span overlap designs, setting registration point stiffness around 200 kN/m with 2 m spacing minimizes both the standard deviation and range (max-min difference) of contact force.(2) Regarding continuous mid-span overlap designs, the two-wire contact line expansion fitting demonstrates superior performance over the three-wire type, and its combination with 140 kN/m registration point stiffness and 4.5 m spacing ensures reliability during high-speed operation.(3) For rigid-flexible transition sections, significant improvements in contact force during bidirectional pantograph passage are achieved by adopting simple catenary suspension, extending the conductor rail length from 2.78 m to 5.4 m, and transitioning the rigid catenary registration point stiffness from a uniform value to a segmented progressively-varying configuration—resulting in smoother, more uniform elasticity transitions with standard deviations meeting all relevant standards.(4) The optimized transition parameters effectively reduce pantograph-catenary wear by minimizing contact force dispersion and extreme deviations, thereby establishing crucial design criteria for 250 km/h rigid catenary systems.

Research purposes: Nanjing Railway Hub is the core node of the railway network in the Yangtze River Delta region, and the layout optimization of its EMU supporting facilities is of strategic significance for the efficient operation of the regional railway network and the improvement of service quality. The purpose of this study is to systematically analyze the current situation and planning of EMU facilities in Nanjing Station, Nanjing South Station, and Nanjing North Station, reveal the key problems such as the inadequate balance of maintenance capacity and the lag of informatization level, and put forward the optimization strategy of integrating regional collaboration and intelligent technology, so as to support the integrated development of the railway network in the Yangtze River Delta region.
Research conclusions: (1) Although the supporting facilities of Nanjing Hub’s EMU have formed a large-scale layout, there are bottlenecks such as long-term shortage of storage tracks, unbalanced maintenance capacity, and lagging informatization.(2) Through facility reconstruction and expansion, intelligent technology upgrading and regional coordinated development, the capacity gap can be effectively alleviated and the overall efficiency of the hub can be improved.(3) The research results provide a theoretical and practical reference for the optimization of EMU facilities in large railway hubs, and lay a foundation for the high-quality railway development in the Yangtze River Delta.

Research purposes: With the deepening implementation of China's new urbanization strategy, the population continues to concentrate in central urban areas. The renovation and expansion of existing underground space represent a crucial means of achieving the full utilization of underground spatial resources, with the networked expansion of urban rail transit underground space serving as a typical example. Based on the investigation of current types of underground space expansion projects and their associated issues, this paper systematically analyzes the differences between newly constructed and expanded underground projects, and proposes the key technologies for horizontal and vertical expansion of existing urban rail transit underground space.
Research conclusions: (1) The renovation and expansion projects for underground structures in urban rail transit can be classified from three aspects. The expansion technologies for various types of underground projects in urban rail transit are analyzed from two aspects: horizontal connection and joint, vertical expansion (adding levels) and crossing traversal. (2) The research proposes that the large-stiffness C-shaped interlocking beam can achieve zero leakage at new-to-existing structure interfaces in horizontal connection and joint projects. It identifies vertical supports as the key element for controlling stress release at the tunnel vault and mitigating settlement deformation during the excavation and expansion of existing tunnels. (3) For zero-distance vertical expansion beneath operational metro stations, the study proposes an active vertical load-transfer underpinning system utilizing the center pilot tunnel method. Furthermore, for over-crossing expansion above operational tunnels, it introduces the skip excavation technique for foundation pits or shafts, which can effectively mitigate rebound heave deformation induced by stratum unloading above the tunnels. (4) The research findings can provide valuable references for upcoming underground space renovation and expansion projects.

Research purposes: Against the backdrop of China's national initiative to promote technological innovation in the civil engineering industry and to implement the "Dual Carbon" strategy, prefabricated structure technology has received widespread attention. To accelerate the application of prefabricated technology in underground engineering and promote the high-quality development of rail transit engineering, it is necessary to conduct research on prefabricated technology in underground engineering. By studying the flexural bearing capacity of full-scale composite panel components and combining with finite element software calculation analysis, the stress performance of prestressed composite components is verified, and this provides a reference for the application of prestressed composite panels in underground engineering.
Research conclusions: (1)Through full-scale testing of composite panels, the stress performance and crack development patterns of composite panels were studied. Based on a comparative analysis of the first and second stage stress characteristics, the differences in load transfer mechanisms of composite panels were revealed, providing reference for the design of underground engineering composite panels.(2)The interface of prestressed composite panels is treated with roughening or water washed exposed aggregates, which can effectively improve the shear resistance of the composite surface, and its stress characteristics are equivalent to those of the overall cast-in-place structure.(3) The stress mechanism of prestressed composite panels is manifested as the tensile steel stress developing faster than the theoretical value (stress ahead), the concrete strain growth in the compression zone is slower (strain lag), and the overall structural performance meets the design requirements.(4)The research results of this study can provide reference and guidance for the design and construction of prefabricated underground projects using prestressed composite slabs.

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: The design alignment parameters of the common-speed railways in China and France are different, resulting in significant differences in alignment design standards.Therefore,it is necessary to compare and analyze the design parameters of the alignment plan and profile in order to determine the reasonable main technical standards. When adopting the standard design of French common-speed railway, it is necessary to analyze its calculation principles, formulas and parameters. In this paper, the main design parameters of the common-speed railways in China and France are studied and analyzed, and the corresponding technical standards are given, which has strong reference significance and guiding role for the design of similar projects.
Research conclusions: (1) In France, the maximum speed of common-speed railway passenger transport is 220 km/h, the freight speed is generally 100 km/h in plain areas, 80 km/h in mountainous areas, and 70 km/h in some specific projects. (2) The maximum superelevation of the French common-speed railway is generally 160 mm, and is 180 mm under difficult conditions. For lines with a speed of 200 km/h, the deficient superelevation is allowed to be 150 mm,and 160 mm in difficult cases; the allowable surplus superelevation is generally 110 mm, and is 130 mm in difficult cases. The superelevation time-variant rate is generally 50 mm/s, and is 60 mm/s in difficult cases; the deficient superelevation time-variant rate is generally 75 mm/s, and is 90 mm/s in difficult conditions. (3) The calculated value of the minimum curve radius of the alignment plane is small, and it should be appropriately adjusted in practical application in combination with the passenger and freight volume, terrain features, rail wear, etc. (4) The maximum slope of French freight railways generally shall not exceed 13.5‰; the minimum length of the slope section is generally 0.5V, and is 0.4V in difficult conditions. (5) The comparative analysis of the alignment design standards for the common-speed railways in China and France is of great significance for guiding the design of similar railways both domestically and internationally.

Research purposes: In recent years, the achievement of key railway projects under the Belt and Road Initiative (BRI) has accelerated,however, "Pan-Consulting work" such as planning, survey and design, and project management is mainly carried out in the traditional way of entrustment by stages and types, which are obvious shortcomings in the traditional consulting mode in terms of responding to risk challenges, progress control, and efficient coordination. This paper analyzes the actual cases on the selection and actual effect of the design consulting mode used in the China-Laos Railway,and conducts a comparative analysis and evaluation by combining qualitative and quantitative methods, so as to use the systematic advantages of the life cycle consulting mode to solve the above problems.
Research conclusions: (1) Based on three dimensions of stakeholders, project life cycle stages and consulting services, a total of 11 indicators affecting the benefits of major foreign railway projects are selected from five dimensions of railway scale, benefit enhancement, work period reduction, quality improvement and risk control, and the benefit evaluation system of the life cycle consulting service for BRI key railway construction is established,a combination of hierarchical analysis and entropy value method is used to assign weights to the relevant indicators.(2) “Gray correlation degree and ideal solution method”is applied for evaluation, supported by experts' opinions, the evaluation and ranking of major foreign railway projects are carried out,for projects adopting the life cycle consulting mode and projects which adopt a phased consulting mode or not use life cycle consulting mode. (3)The research results demonstrate that the life cycle consulting mode offers distinct advantages for major overseas railway projects. It effectively mitigates risks and enhances value in terms of quality, cost-effectiveness, and timeline management.