To improve the visualization of switch machine status monitoring and the intelligence of fault diagnosis by urban rail transit operators, a 3D visualization monitoring and fault diagnosis method of switch machine based on digital twin is proposed, which provides a powerful technical support for the realtime monitoring of switch machine status, highquality transmission of operation data, and the precise alarm of equipment faults. Compared with the existing intelligent operation and maintenance system of Switch Machines, this study uses digital twin technology to establish a highfidelity model, maps the fieldworking Switch Machines in the information space through realtime interaction of data, and realizes threedimensional visual monitoring of Switch Machines indoors through WebGL and model lightening technology; in view of the small number of samples of fault data for switch machines in the field, it establishes a combined model of CNNTransformer to achieve fault diagnosis. To achieve the fault diagnosis of switch machines, the fault diagnosis accuracy rate is 98.67% under the condition of imbalance between normal data and fault data; In order to verify the feasibility of the proposed framework and the improved algorithmic approach, a 3D visualization monitoring and fault diagnosis platform for switch machines based on digital twins is designed.

Addressing the current challenges in urban rail transit line reconstruction, such as insufficient network synergy, path dependency in equipment updates, and the lack of upgradability design, this study explores theoretical innovation directions. It proposes key strategies, including incorporating upgradability into the equipment performance evaluation system, decoupling equipment from lines for networkoriented reconstruction, and improving the overall network functionality through clustered line reconstruction. These theoretical innovations aim to systematically promote the reconstruction of existing lines, reduce the cost of equipment upgrades, improve maintenance efficiency, and drive the sustainable development of the urban rail transit industry. Based on the framework of Guidelines for reconstruction of existing urban rail transit lines in China, this study addresses critical challenges in urban rail transit reconstruction, including insufficient network coordination, path dependency in equipment upgrades, and inadequate upgradability design. It proposes a comprehensive theoretical framework with four key innovations: integrating "upgradability” into equipment performance evaluation systems; implementing networkoriented decoupling of equipment systems from physical infrastructure; enhancing overall network functionality through clustered line reconstruction approaches; and developing derivative, regenerative, and symbiotic systems for rail transit reconstruction based on the "productionlivingecology" theory of urban renewal. These theoretical advances provide systematic solutions to optimize network functionality, reduce equipment replacement costs, enhance maintenance efficiency, and promote sustainable development in the urban rail transit sector. The proposed framework offers valuable guidance for policymaking and implementation strategies in urban rail transit modernization.

Traditional fiber optic sensing methods mainly focus on onedimensional or twodimensional displacement monitoring of tunnel segments, making it difficult to effectively monitor threedimensional deformation between segment rings. This paper proposes a diamondshaped layout scheme based on distributed fiber optics, establishing a threedimensional deformation monitoring method suitable for shield tunnel segments. By analyzing the threedimensional deformation patterns of tunnel segments, three methods for calculating segment displacement are introduced. To validate the effectiveness of these methods, a simple and operable experimental device simulating threedimensional deformation of tunnel segments was designed, and indoor tests were conducted. The test results were compared with theoretical calculations, confirming the effectiveness of the proposed diamondshaped fiber optic layout for segment deformation monitoring, as well as the rationality of the three displacement calculation methods. The results demonstrate that the diamondshaped distributed fiber optic sensors, combined with the Kvalue decomposition method, provide optimal monitoring performance for segment displacement. The implementation of Brillouin Optical Time Domain Analysis (BOTDA) technology enables extensive realtime monitoring of tunnel segment displacement variations.

Redundancy is a crucial component of network resilience. To address the current gap in time redundancy consideration when identifying critical stations in rail transit networks, this study proposes a comprehensive approach. First, we develop a timeweighted rail transit network model incorporating Space L and multiline coupling, which accounts for interstation transfer times. Second, we employ node deletion to simulate station disruptions and introduce three metrics: station redundancy index, network redundancy index, and a redundancy evaluation model based on shortest travel time variations. Using the 2024 Chongqing rail transit network as a case study, we compare the results between redundancybased and betweennessbased evaluations. The analysis reveals an average station redundancy index of 0.7998, with 3.87% of stations showing a Kmeans clustering center of 0.2788, indicating lower redundancy at critical locations. Redundancycritical stations are predominantly located near the network periphery along extended lines, while betweennesscritical stations are typically found at multiline interchange points, demonstrating distinct spatial patterns between these two categories. Network performance is more significantly impacted by disruptions at redundancycritical stations compared to betweennesscritical stations, validating the effectiveness of our identification method. This approach provides valuable insights for enhancing the resilience of urban rail transit networks.

Relying on a subway station entrance and exit channel pipe jacking project, combined with the onsite monitoring data for jacking parameter inversion, the refined pipe curtaincorridorstrata pipeline corridor jacking finite element model considering the locking joints was established. The deformation of strata with and without pipe curtain is analyzed comparatively, and the necessity of pipe curtain is verified. Then, the effects of pipe diameter, pipe spacing and pipe thickness on surface settlement, pipe curtain cost and joint gap were systematically investigated through comprehensive tests, and a comprehensive evaluation system of TOPSIS was established to evaluate the adaptability of the pipe curtain with game combination assignment. Subsequently, BPNN was used to fit the mapping relationship between the pipe curtain parameters and the adaptability, and finally the genetic algorithm was used to search for the optimal parameter combinations. The study shows that the parameter that has the greatest influence on the adaptability of the pipe curtain is the diameter of the steel pipe, followed by the clear distance of the steel pipe, and finally the thickness of the steel pipe. Considering the safety, water resistance and economy, the recommended design parameters of the locking pipe curtain are the steel pipe diameter of 990 mm, the steel pipe thickness of 20 mm, and the steel pipe clearance of 160 mm.

This paper analyzes the power supply system of suspended monorail transit and emphasizes the necessity of DC system ground fault protection to ensure equipment and personnel safety under various operating conditions. While conventional voltagebased ground fault protection devices can provide basic protection functions, they lack selective tripping capability and may expand the fault area. Based on Kirchhoff's current law, this paper proposes an innovative sectional currentbased ground fault protection scheme. Through the implementation of inverse timecurrent characteristics and differential current components, the scheme achieves accurate and rapid fault section identification, enabling priority tripping of corresponding sections to isolate faults, thus significantly improving system selectivity. Through analysis of protection objectives, coverage, types, and operation time limits of both 64D protection and frame current protection, the study concludes that these two protection methods are complementary and can operate simultaneously. Field applications demonstrate that all protection functions perform sensitively and reliably. By calculating key parameters for 64D protection, this paper proposes protection schemes and system setting values for practical engineering applications, optimizing protection system selectivity, effectively reducing fault ranges, and ensuring operational safety.

This paper addresses the challenges in onsite engineering acceptance testing of urban rail transit signaling systems in China, which currently face issues such as singlemethod approaches, lengthy cycle times, low efficiency, high costs, and heavy workloads. A method for automatic generation of onsite engineering acceptance test sequences is proposed. The methodology involves three main steps: First, analyzing the constraints of interconnection test case sets for urban rail signal systems; second, dividing the line into independent test sections; and third, converting line characteristics into computerrecognizable formal language to enhance editing efficiency and humancomputer interaction. The proposed method employs an “auxiliary generation tool" to automatically generate fieldexecutable engineering acceptance test sequences. The effectiveness of this approach is validated through tests on actual railway lines. Results demonstrate that test sequences designed using formal language meet engineering acceptance requirements, achieve 100% coverage of interconnection test cases, and significantly reduce field testing time while improving efficiency compared to traditional manual test sequence design methods.

Traction current return system is an important part of traction power supply system. System failures can damage primary and secondary equipment and potentially disrupt train operations. At present, there is limited research on realtime measurement of traction return current distribution for 25 kV AC power supply system subway. This study presents a synchronous testing methodology for measuring current in individual return cables to study return current distribution patterns and verify limitations in SCADA system monitoring. Based on return paths, the current is divided into three groups: station return, parking lot return, and ground return. The study analyzes the proportion and variation pattern of return current in different paths and compared findings with SCADA return current data. Results indicated that despite significant temporal fluctuations in return current magnitude, the distribution ratio remains stable most of the time, with only occasional variations. The average distribution ratios across different time periods vary by less than 1%. However, the SCADA system fails to accurately reflect return current changes. This research establishes return current distribution ratios through empirical testing, providing reference values for similar substations and directions for improving SCADA system monitoring capabilities.

This studyexplores the impact mechanism of population socioeconomic, land use, station characteristics, and other transportation attributes on rail transit passenger flow. Using multisource data including LandScan population grid, points of interest (POI), and automatic fare collection system (AFC), a spatiotemporal geographic weighted regression, gradient boosting regression tree, Shapley addition explanatory (GTWRGBRTSHAP) model, was developed to analyze the spatiotemporal heterogeneity and nonlinear effects of the these factors. A case study was conducted using data from Tianjin rail transit network, and the results showed that the mixed model effectively captures the spatiotemporal heterogeneity and nonlinearity between influencing factors and passenger flow. Factors such as population density, officetype land, shopping and leisure land, and betweenness have significant spatiotemporal differences in their impact of passenger flow. Factors such as residentialtype land, transportation facility land, land use entropy, and betweenness have significant complex nonlinear and threshold relationships with passenger flow. The above results provide strategic references and theoretical support for optimizing public transportationoriented urban development (TOD) planning and improving the efficiency of rail transit passenger flow.

The Beijing Northeastern Ring suburban railway renovation project aims to transform the line into a public transitstyle operation, with portions of the route cooperating on shared tracks with Subway Line 19. While enhancing passenger service, the line must preserve its critical function as a connector within the main railway network. The system design requires a maximum throughput of 20 train pairs per hour. The existing Changping Station, which serves as both a turnback station for the Northeastern Ring Line and a connection point to the vehicle depot, is characterized by its large scale and operational complexity, making it the bottleneck for system capacity. This station becomes the critical factor in determining whether the system's maximum capacity requirements can be achieved. The Northeastern Ring Line adopts the CTCS2 train control system with ATO and automatic turnaround capabilities. To enhance Changping Station's capacity and meet system requirements, modifications were implemented to the existing station layout and signaling system. The station tracks, throat areas at both ends, and connections to the main line were optimized. Combined with signaling improvements and verified through traction calculations and multiscenario timetabling, Changping Station ultimately achieved a throughput capacity of 23 train pairs per hour, not only satisfying system requirements but also providing a 15% capacity margin. Through comprehensive analysis of Changping Station's capacity, the study identified that the number of arrival and departure tracks, length of station throat areas, signal configuration, and operating speeds are the primary factors limiting station capacity. The paper proposes solutions for improving station throughput capacity, providing valuable reference for future suburban railway design projects.