To investigate the dynamic impact of straddle-type viaduct construction on existing metro tunnels, this study takes the Wangsheren Station to Wangsheren North Station section of Jinan Metro Line 6 as the engineering background. Field tests and numerical simulations were conducted to systematically analyze the deformation patterns of tunnels under the multi-stage coupled effects of "pile foundation excavation, foundation pit unloading, and bridge superstructure loading." The findings reveal that: (1) Foundation pit excavation induces significant tunnel uplift (maximum 4.62 mm), accompanied by horizontal contraction (maximum 1.74 mm) and vertical expansion (maximum 3.25 mm). After bridge loading, the tunnel subsides, with horizontal expansion and vertical convergence observed. (2) The clearance between the tunnel and foundation pit significantly influences uplift deformation: as the clearance increases from 6.7 m to 20 m, the uplift decreases from 5.74 mm to 0.90 mm (approaching zero at ≥15 m), while subsidence remains stable at approximately 5.2 mm. A clearance of ≥12 m is recommended for risk mitigation. (3) Stratigraphic characteristics dominate deformation responses: silty clay layers exhibit greater uplift during excavation (+1.2 mm), whereas gravelly sand layers experience more pronounced subsidence during bridge operation (–1.5 mm). Deformations in moderately and slightly weathered rock strata are negligible. (4) Interval construction of multiple pile caps reduces subsequent excavation-induced uplift (with a 12% reduction for the second pile cap), supporting a "alternate excavation" construction strategy. Innovatively, this study proposes a deformation prediction model based on stratigraphic heterogeneity, which overcomes the limitations of traditional homogeneous assumptions and provides a theoretical foundation for optimizing the design and risk assessment of straddle-type viaduct projects.

To evaluate and mitigate risks to the structure of a metro station in a cobble stratum under rising groundwater, this study utilized the finite element method to develop a two-dimensional numerical model of a representative cross-section based on a Beijing subway station project. The model reasonably incorporates strength degradation induced by soil wetting and comprehensively examines the structural internal forces, displacements, and evolution of plastic zones within the ground in response to scenarios of groundwater level rise in gravelly deposits. The simulation results show that the base slab, roof slab and sidewalls, as the enclosure structure, all exhibit increased compressive stress on their soil-facing surfaces. The base slab and roof slab bear the horizontal stress from the sidewalls, thereby offsetting part of the mid-span bending moment and reducing the tensile stress. The intermediate slab and the central column, as intermediate supporting members, continue to perform their supporting function effectively. Notably, the slab-column and slab-wall connections are regions of stress concentration and therefore require particular attention to prevent structural cracking or damage caused by excessive stress. In a cobble stratum, both the stratum and station experience uplift, with the station's uplift marginally surpassing the surrounding soil. Structural integrity remains unscathed without local deformation, thus indicating a relatively diminished risk of localized structural harm. The plastic zone is mainly concentrated in areas such as the bottom corners of the sidewalls and does not extend to the ground surface to form a rupture zone, indicating a low probability of overall instability.

To address the problems of aging and deformation of rubber boots, unsupported sleepers and gauge variation caused by long-term operation on existing elastic short-sleeper tracks, and to improve the stability and operational safety of the track structure, this paper proposes a novel treatment technology for unsupported defects in elastic short-sleeper tracks to overcome the low construction efficiency and insufficient repair precision of existing repair methods. This technology combines a novel high-flow repair material with a refined grouting process, enabling complete filling of gaps smaller than 1 mm. Off-site grouting tests verified the feasibility of the material and construction process, and the mechanical properties of the repaired elastic short-sleeper track were evaluated based on static stiffness and fatigue tests. The test results demonstrate that this treatment method effectively fills the unsupported areas and enhances the overall stability of the track structure. It is suitable for the rapid and efficient repair of existing tracks under time and space constraints and has good potential for engineering application.

Surface loading can cause certain deformations in subway tunnels, and excessive deformation will affect the safe operation of subway tunnels. To study the influence of asymmetric surface filling on variable-section subway tunnels, a finite element model of horseshoe-shaped and box-shaped tunnel structures was established based on the road backfilling reconstruction project above the side of a certain underground section of Shijiazhuang Metro. The surface settlement and tunnel stress-deformation patterns during road backfilling construction were analyzed and compared with field monitoring results for verification. Furthermore, the effects of parameters such as tunnel burial depth, loading magnitude, and loading dimensions on the underlying variable-section tunnel were discussed. The results show that: under asymmetric filling, the surface soil displacement field approximately exhibits a "V"-shaped settlement; the maximum surface settlements in the tunnel areas of horseshoe-shaped and box-shaped sections are 15.85 mm and 27.17 mm, respectively; tunnel structural deformation is dominated by vertical settlement with relatively small horizontal deformation; compared with the horseshoe-shaped section tunnel, the box-shaped section tunnel is more significantly affected by surface loading; the deformation of the tunnel at the intersection between the horseshoe-shaped and box-shaped sections shows a certain abrupt change, and cracking and water leakage issues in this junction area require close monitoring during construction; loading magnitude and loading range are positively correlated with tunnel vertical settlement, while the horizontal distance between the loading center and tunnel axis and tunnel burial depth are negatively correlated with tunnel vertical settlement; the loading range has a significant influence on the distribution range of tunnel settlement. When the tunnel burial depth exceeds 24 m or the horizontal distance between the loading centerline and tunnel axis exceeds 50 m, surface loading has almost no effect on tunnel settlement.

Because the operating conditions of urban rail transit systems are highly variable and load fluctuations are severe, traditional energy-saving methods based on static scenarios struggle to accommodate dynamic load demands effectively. Therefore, load scenarios must be accurately identified, and an energy-saving optimization method for flexible traction power supply systems is needed to achieve dynamic "scenario-strategy" matching and improve energy-saving performance. Accordingly, an energy-saving optimization approach for urban rail transit flexible traction power supply systems considering multiple load scenarios is proposed. First, a k-Medoids load clustering method based on t-SNE is designed. A strategy of clustering after dimensionality reduction is adopted to more accurately reflect the correlations between system load and operating periods and seasons. Second, an energy-saving optimization model for the flexible traction power supply system is constructed. Based on an intelligent optimization algorithm, the virtual resistance of traction substations is adjusted to minimize the total incoming energy of the system. Through simulation validation, the effectiveness of the proposed method is verified. The proposed load clustering method effectively extracts the inherent characteristics of the load, reveals the correlation between system load and operating periods and seasons, and identifies six specific operating scenarios. The proposed energy-saving optimization method achieves good energy-saving performance in various operating scenarios, with a maximum energy-saving rate of 4.07%. The energy-saving optimization method for urban rail flexible traction power supply system based on load clustering has connected the complete chain of "scene recognition-strategy matching-dynamic adjustment", which can provide important technical support for energy-saving operation of urban rail transit.

To address the problems of high energy consumption and lagging thermal environment regulation in traditional air-conditioning systems of metro stations, this study proposes a dynamic thermal environment management system integrating nature-like wind technology with spatially gridded monitoring, CFD pre-simulation, and equipment-linked control. In the reconstruction project of Nanhu Station of Nanning Rail Transit Line 1, 45 sensors were deployed to construct a gridded monitoring network, and the layout of monitoring points and fan positions was optimized based on CFD pre-simulation. A hierarchical control strategy centered on perceived temperature was developed to realize the intelligent linkage between air conditioners and nature-like wind fans, so as to achieve the energy-saving effect of the air conditioning system. The results show that when the ambient temperature rises to 29℃, the system enhances turbulent heat dissipation (wind speed 0.8–2.5 m/s), making the perceived temperature equivalent to 27℃; the PMV value drops to 0.8–1.2 (PPD≤19%), and the comprehensive energy-saving rate in the air conditioning season reaches 32.1%. The system provides a replicable technical pathway for the green renovation of metro stations.

To address the problem of insufficient operating speed caused by step-by-step setting coordination in traditional definite-time overcurrent protection for load-switch-based medium-voltage ring networks in urban regional railways, this paper proposes a fast protection method based on differential current. The fault section is identified using the fault characteristics of differential current, and the fault information is transmitted to the master station via the GOOSE network. The master station then controls the tripping of the outgoing circuit breaker at the substation to achieve rapid fault clearance. At the same time, the outgoing current of the substation is monitored. When the outgoing current drops below the preset threshold, a command is sent via the GOOSE network to control the tripping of the load switches on both sides of the fault section, completing the fault isolation. After fault isolation, the circuit breaker at the substation outgoing line and normally open point are closed to restore power supply to the healthy area. Simulation results show that under different fault types, locations, and transition resistances, the proposed method can achieve rapid protection operation and effective fault isolation, significantly improving protection speed and providing a reliable guarantee for the safe and stable operation of the load-switch-based medium-voltage ring network in urban regional railway systems based on load switches.

Due to the large quantity of equipmentin environmental control rooms, it is necessary to optimize the equipment layout to save space while guaranteeing normal maintenance. Therefore, an automatic spatial optimization approach is proposed to optimize the layout of central chiller plants. A repulsion model is adopted to quantify the rationality of equipment layout, which was regarded as the optimization objective. The differential evolution algorithm is utilized to adjust the equipment layout within a given space for the lowest optimization objective. Moreover, this approach repeatedly reduces the given space to minimize the space occupation of the central chiller plant. A real metro station environmental control room was taken as the case to verify the effectiveness of the proposed approach. Results indicate that the proposed approach reduced the occupied area of the equipment from 105 m² to 100.1 m², with reasonable equipment spacing maintained. Therefore, the proposed approach is able to optimize equipment layout for metro station environmental control rooms, thereby achieving room space saving and reasonable equipment spacing.

The index system dominated by key performance indicators (KPIs) has problems such as siloed fragmentation among departments, alienation of incentive functions, and insufficient process supervision. In the face of the era opportunities of smart urban rail construction and high-quality development, it is necessary to explore and design a new performance index system that can better help enterprises transform their strategic vision into an executable path. The mature objectives and key results (OKR) method is proposed as the core idea of optimization design. Guided by "departmental internal-control indicators－vertical alignment indicators-horizontal coordination indicators" and following the logical chain of "goal hierarchy-task quantification–closed-loop results", the proposed system builds departmental internal-control indicators to strengthen process management, establishes strategic empowerment indicators aligned with departmental responsibilities to reinforce positive incentives, and introduces cross-departmental coordination indicators through a four-level linkage mechanism of "strategy–process–department-post." Taking Shanghai Metro as the research object, this study designs a new indicator system, including department-level and field-level lists of "strategic objectives–key results–empowerment indicators", as well as a list of cross-departmental horizontal coordination constraints. Since its trial implementation in December 2024, employees' trust in the evaluation results has steadily increased. Organizations at all levels can not only easily trace key-result implementation processes and monitor progress, but also more efficiently identify the underlying causes behind observed problems and more promptly formulate targeted improvement measures.

With reference to internationally recognized statistical standards, this study classifies urban rail transit into three major modes—metro, light rail, and tram. In addition, commuter rail is incorporated to enable a broader-scale assessment of the global operational landscape of rail-based urban passenger transport and to inform China's rail transit development. By the end of 2025, 562 cities across 79 countries and regions worldwide had urban rail transit in operation, with a total operating length of 46,528.95 km. Metros, light rail, and trams accounted for 22,789.91 km (48.98%), 6,469.95 km (13.91%), and 17,269.09 km (37.11%), respectively. Over the same period, 65 cities in China (including Hong Kong, Macao, and Taiwan) operated urban rail systems totaling 13,796.06 km, of which the Chinese mainland accounted for 13,071.58 km and Hong Kong, Macao and Taiwan for 724.48 km. For metro ridership, data from 190 cities in 61 countries indicate that metro systems carried 76.051 billion passenger trips in 2024, with an average load intensity of 0.99×10⁴ passenger trips per (day·km). In China (including Hong Kong, Macao, and Taiwan), metro ridership reached 33.541 billion passenger trips in 2024, representing 44.10% of the global total. Overall, China's urban rail transit has continued to expand steadily and ranks first worldwide in both network length and passenger volume. With respect to commuter rail, 241 cities in 54 countries and regions had commuter rail services in operation by the end of 2025, with a total operating length of 70,001.16 km. China (including Hong Kong, Macao and Taiwan) had commuter rail services in 31 cities, totaling 4,345.73 km and accounting for 6.21% of the global total. These figures suggest that, as China enters the 15th Five-Year Plan period, there remains considerable room for enhancement in both the overall scale and network structure of commuter rail development.