Traditional steel struts cannot be tensioned, and the construction of concrete struts is complex and generates considerable construction waste during the demolition phase. Therefore, prestressed steel struts capable against tensile and compressive stresses have been invented. The performance evaluation results of mechanics, construction adaptability, and cost with a prestressed steel strut capable against tensile and compressive stresses show that its compression bearing capacity is the same as that of a traditional steel strut and equivalent to that of a concrete strut. Furthermore, its tensile and strut stiffness performances are equivalent to those of a concrete strut and superior to those of a traditional steel strut. Its construction convenience is equivalent to that of a traditional steel strut and 20%30% lower than that of a concrete strut. The first concrete strut replaced by a prestressed steel strut capable against tensile and compressive stresses for metro excavations can not only ensure technical performance but also result in better economic and social benefits.

To explore the stress and deformation characteristics of an existing tunnel caused by foundation pit dewatering, a threedimensional numerical model was established based on an actual project. Taking the maximum vertical displacement of the tunnel as the evaluation index, an orthogonal table is used to screen the optimal combination and the main influencing factors. Then, the main influencing factors are analyzed via univariate analysis to study the stress and deformation law of the tunnel. The results of the range and variance analyses showed that the insertion depth of the diaphragm wall was the main factor affecting the maximum vertical displacement of the tunnel outside the pit. Therefore, when a new foundation pit project adjacent to an existing tunnel has a dewatering demand, this factor can be selected first to control tunnel deformation. As the insertion depth of the diaphragm wall increases, the bending moment and deformation of the tunnel decrease. After the insertion depth of the diaphragm wall reaches a soil layer with poor water permeability, the tunnel deformation decreases significantly. At this time, the deformation of the tunnel can be effectively controlled; however, controlling the deformation of the tunnel by increasing the insertion depth is of little significance. The dewatering causes the adjacent tunnel outside the pit to produce "horizontal duck egg" settlement deformation toward the pit, obliquely downward, and the deformation of the tunnel vault and the side arch waist of the adjacent foundation pit should be emphasized during the construction process.

To explore the influence of a cavity on a shield tunnel, a refined numerical model of a shield tunnel, considering ring and longitudinal joints, is established. The variation law of the internal force, deformation, and section safety factor of the segment are investigated under various conditions, such as the depth, area, and location of the cavity. Additionally, the influence of different assembly points of the segment on a tunnel with a cavity behind it is discussed. The results indicate that the order of the adverse effects of cavities at different positions behind the tunnel on structural safety is tunnel waist > tunnel bottom > tunnel top. When the cavity area is 5.0 m², with an increase in the cavity depth, the bending moment and safety factor of the tunnel section at the center of the tunnel top or bottom cavity first decrease and then increase in the opposite direction, and the ellipticity of the segment first decreases to 0 and then increases in the opposite direction. The bending moment is reversed when the cavity depth was 0.3 m or 0.2 m. The safety factor of the section at the center of the left tunnel waist cavity decreases continuously, and the ellipticity of the duct piece and the bending moment increase significantly. When the cavity depth is 0.5 m, the bending moment of the tunnel section at the center of the cavity at the top or bottom of the tunnel is reversed when the cavity area is 3.75 m². The existence of circumferential joints within the cavity reduces the internal force of the tunnel section at the center of the cavity and improves its safety factor. However, its maximum joint opening is 2.03.5 times that of a cavity without a joint. The results provide a reference for the safety evaluation of the cavity behind the lining of a shield tunnel and the selection of assembly points.

To address the problems of “insufficient maintenance” and “excessive maintenance" in existing maintenance modes, a health status grading evaluation method for subway power supply equipment that considers the importance of indicators is proposed. First, the equipment health value was solved according to a combination of an analytic hierarchy process and fuzzy statistics. The importance of the index was considered, and the health status of the equipment was graded. Finally, a drytype transformer was considered for analysis. The results show that the obtained results can reasonably characterize the health status of the subway power supply equipment, which is consistent with the actual situation, and verify the accuracy and feasibility of the method.

This study proposes a solution involving the use of a longitudinally induced ventilation system to solve ventilation challenges in factory buildings within a covered metro vehicle base, where natural ventilation is impractical and traditional horizontal ventilation systems are difficult to implement. We first created a threedimensional model for the longitudinally induced ventilation system, analyzed the impacts of the induced jet fan installation spacing and height on the airflow within the factory building based on numerical simulation results, and validated the proposed system against actual engineering conditions. The results indicate that the best overall and workstation ventilation effects can be achieved with installation spacings of 20 and 25 m, respectively, along with heights of 8 and 6 m, respectively, for the induced jet fans inside the factory building. The field tests agreed well with the simulation results. This study provides a theoretical basis for the application of longitudinal ventilation systems in engineering applications.

Studying the distribution characteristics and mechanisms of urban rail transit accidents is important for ensuring operational safety and formulating safety control measures. This study statistically analyzes 425 local and international urban rail transit operation accidents from 1970 to 2022 and compares and analyzes the causes and time distribution characteristics of operation accidents. Based on the cause mechanism and principal component analysis method, a safety evaluation system for urban rail transit operations was constructed, and a combined weight evaluation method based on game theory was proposed. Taking the data of 274 operational accidents in China from 1990 to 2022 as an example, combined with expert scoring, the safety status of urban rail transit operations in China was analyzed from a macro perspective. The results indicated that the factors causing operational accidents included personnel, equipment, and environmental factors. Among them, domestic and foreign operational accidents caused by equipment accounted for the highest proportion of accidents, accounting for 56% and 65% respectively. January, March, July, August, and December were the months with frequent accidents, which were the same as the peak months of passenger flow. The combination weighting method not only considers the amount of information in objective statistical data but also combines the experience accumulation of subjective experts, which makes the evaluation results closer to the actual operation situation and proves the feasibility of the evaluation method.

Aiming at the optimization problem of lasttrain connection planning in urban rail transit networks, which often brings difficulties in successful transfers, this study selects the arrival times of the last trains as decision variables and constructs a mixedinteger linear programming model to minimize the number of failed passenger transfers. To address the high model complexity caused by the expansion of the network scale, a quantum computing method is adopted to solve the proposed model. First, the original model is reconstructed into a twostage problem with a smaller computation scale. Then, the firststage optimization model is transformed into a quadratic unconstrained binary optimization (QUBO) model that can run on a quantum computer. Algorithm development and experimental testing are conducted based on the optical quantum computing technology of the coherent Ising machine. To verify the effectiveness of the proposed method, we consider the Beijing subway network as an example. The quantum computing results are compared with those from commercial solvers, confirming the feasibility of both the model transformation method and the quantum computing approach proposed in this study. These findings provide technical support for the further application of quantum computing in solving complex optimization problems in rail transit.

This study employs prevalent international statistical standards to categorize urban rail transit into three types: metro, light rail, and tram. It presents a comprehensive statistical analysis of the current state of urban rail transit systems across the globe. As of the close of 2023, urban rail transit systems have been established in 563 cities spanning 79 countries and regions, with a cumulative track length exceeding 43,400.40 km. Subways, light rails, and streetcars account for 50.07%, 10.69%, and 39.24% of the total length, respectively. Notably, as of December 31, 2023, 66 cities in China (including Hong Kong, Macao, and Taiwan) have commenced rail transit operations, boasting a combined operational track length of 11,900.29 km, with Chinese mainland alone contributing 11,232.65 km to this total. In 2022, the metro systems in 183 cities across 59 countries globally handled a total of 58,652 million trips of passengers, representing an average ridership intensity of 0.81 trips per day per kilometer. Specifically, China's metro systems (including those of Hong Kong, Macao, and Taiwan) registered an annual passenger traffic volume of 21.251 billion trips. The study underscores the steadfast advancement of China's urban rail transit systems, which consistently lead the world in both network scale and passenger traffic. Through an indepth analysis of data subsequent to the release of Document 52 by the State Council, this study anticipates a resurgence of lowcapacity urban rail transit systems, particularly streetcars, in Chinese mainland, especially in the central and western regions, in a bid to drive environmentally sustainable urban development. Further, by drawing on data from major countries and cities worldwide, both preand postpandemic, the study predicts a return of passenger traffic in Chinese mainland to prepandemic levels by 2024-2025.

This paper provides a comprehensive overview of Chinese mainland's urban rail transit development in 2023. By the end of the year, 28 provinces and 59 cities had 338 urban rail transit lines in operation, spanning 11,232.65 km. Subway lines made up 76.10% of this length, with 8,547.67 km, followed by fully automatic operation (FAO) lines with 9.37% and 1,052.43 km. The network expanded by 884.55 km in 2023, with 53 new lines (or sections) opening, including 539.50 km of subway lines and 252.79 km of FAO lines. The new lines involved 7 different system types and 30 cities, 3 of which inaugurated their first urban rail transit systems. In 2023, Chinese mainland's urban rail transit network also set a new record of annual passenger volume, surpassing 80 million passenger trips per day on average.

With rapid urbanization, the refurbishment of urban railway lines is crucial for advancing highquality urban rail development and sustainable urban growth. This refurbishment process presents a host of intricate professional challenges that must be addressed. Meeting current requirements for line reconstruction while addressing safety issues and expanding beyond traditional specialized fields is demanding. Therefore, it is essential to chart a development path for the transformation of existing urban rail transit lines in line with the needs of highquality urban rail development. Drawing on the history of Beijing's line refurbishments, this study examines the challenges and future objectives of urban rail transit line refurbishment and proposes comprehensive concepts for the rejuvenation process. Furthermore, we introduce an innovative approach to investment and financing for line refurbishments, focusing on sustainable urban rail development. We offer recommendations for the transformation of urban rail transit lines in China across six key areas: system development, vitality of components, investment and financing frameworks, technological empowerment, research and development, and relevant standards.