In order to address the issue of longterm dependence caused by the extended time span of wheel wear data and improve the prediction accuracy, an improved BiLSTM metro wheel wear prediction model is proposed by optimizing Bidirectional long shortterm memory network (BiLSTM) with Sparrow search algorithm (SSA). Firstly, the hyperparameters of the BiLSTM algorithm, such as the number of neurons, iteration count, input batch size, and learning rate, are optimized using the SSA. This optimization process is conducted within a specified range to obtain the optimal values of these hyperparameters. This optimization process aims to obtain the optimal parameter values. Subsequently, the SSABiLSTM network model is constructed using these optimal parameter values to predict and analyze wheel wear. Tread wear and flange wear are taken as the research objects, and the measured historical wear data of wheel No.1 of the metro’s carriage # 1 are used as inputs to metro and validate the model, and compare the prediction results with those of MLP, LSTM, BiLSTM and SSA-LSTM models. The results show that the improved bidirectional long short-term memory network model has higher wear prediction accuracy, and the mean absolute percentage error (MAPE) of tread wear is reduced by 13.28%, 10.32%, and 1.47%, and flange wear by 9.5%, 0.46%, and 0.02%. The wear of the No. 1 wheel of the same metro No.2 and No.4 cars is predicted and compared with the measured wear data. The average absolute percentage error of tread wear is 1.34% and 1.42%, respectively, and the average absolute percentage error of rim wear is 0.18% and 0.19%, respectively. The results confirm that the model exhibits strong generalization capabilities. The wheel wear prediction model based on improved BiLSTM network (SSA-Bi-LSTM) has high prediction accuracy and good generalization, which provides theoretical support for the intelligent management of metro wheelsets and prolongs wheel service life.

The current evaluation system for the sustainable development of urban rail transit often employs a simple hierarchical weighted summation method. However, this method does not account for the interactions among indicators at the same level or the multiple effects of lowerlevel indicators on upperlevel indicators, thus failing to reflect the actual sustainable development status systematically, comprehensively, and accurately. To address this issue, this study introduces a new evaluation approachthe ESE (EconomicSocialEnvironmental) evaluation theory and method. This approach builds on the new understanding that data impacts the three dimensions of economy, society, and environment. An ESE spatial Cartesian coordinate system is constructed to represent all operational scenarios of urban rail transit. Within this threedimensional ESE space, the sustainable development status of urban rail transit is classified into "eight types and four categories," allowing for the quantification of sustainability levels and enabling a threedimensional visual representation.

A switch machine is a core equipment of a signal system with the largest maintenance volume, strongest maintenance difficulty, and a wide range of equipment failures. With the increase in intelligent operation and maintenance research in the urban rail transit industry, research on intelligent operation and maintenance of switch machines has attracted the interest of industry scholars. It is the foundation for achieving intelligent maintenance of urban rail signals and intelligent operation and maintenance production organization modes. This article summarizes the limitations of traditional microcomputer monitoring systems and proposes an intelligent system based on the maintenance difficulties and pain points of switch machines in the industry. The system includes critical state perception, intelligent fault diagnosis, critical state warning, and health assessment, and proposes specific implementation methods. The system was successfully applied to Nanning Metro Lines 4 and 5, and significant benefits were obtained.

The mechanical behaviors of Ushaped girders in urban rail transit differ in the spanning and transverse directions, and a dynamic coefficient of 1.40 in the current design code will result in material waste. Considering the bidirectional stressing characteristics, the Ushaped girder of the Nanjing Subway Line S6 Urban Rail Transit was selected as a case study, and a trainbridge coupling dynamic model was established. The effectiveness of the model was verified by comparing the test and calculated results. The dynamic coefficients of the different responses were analyzed by changing the train speed and formation. The results indicate that the girder bottom only bears longitudinal tensile stress but carries both transverse tensile and compressive stresses in the same section. The maximum dynamic coefficients of the deflection, longitudinal stress, and lateral stress were 1.231, 1.216, and 1.362, respectively, in the fulland fixedload cases of the 6car formation. When determining the dynamic coefficients of a singletrack Ushaped girder, the influence of the train formation should be considered, and the values should be distinguished according to the stressing directions. We recommend a value of 1.30 when calculating the deflection and longitudinal stress and 1.40 when calculating the lateral stress. This paper proposes reasonable values for the dynamic coefficients of Ushaped girders and provides a reference for structural optimization.

Rapid urban rail transit growth presents new challenges for operation and management. Traditional methods limit data and resource utilization. China's "strong transportation country" strategy and smart city development necessitate a shift from traditional to digital thinking for subways, a crucial component of resident travel. Digitalization offers the potential to enhance operational efficiency and quality. This study analyzes the challenges of digital rail operations and presents Kunming Metro Line 4 as a case study. It explores Line 4's digital transformation journey, highlighting its economic benefits. By establishing a cloudbased comprehensive automation and business integration management system, Line 4 achieved synchronized digitalization across the enterprise, enabling practical implementation of digital metro operations. This approach reduced costs, improved efficiency, and offers valuable solutions for urban rail transit digitalization within the industry.

This study investigates the wheelrail noise characteristics of urban rail trains passing through longspan bridges, focusing on the Dongshuimen Bridge of the Chongqing Rail Transit Line 6 and the Chaotianmen Bridge of the Chongqing Rail Transit Loop Line. Noise measurement data were collected for trains passing over the bridges. This study analyzed and compared the spectral characteristics of noise, summarizing the relevant patterns. The results indicate that the wheelrail noise generated by rail trains on largespan bridges exhibits a widefrequency characteristic, with the sound pressure level spectrum curve showing a “high in the middle, low on both sides" pattern. The noise peak of steel truss arch bridges is concentrated at approximately 800 Hz, and the structural noise generates a relative peak in the range of 6380 Hz. In contrast, the noise peak of the steel truss girder cablestayed bridges is in a higher frequency range. The threespan continuous steel truss suspension arch bridge exhibits a wide and highamplitude noise spectrum, with its noise being significantly greater than that of the steel truss girder cablestayed bridge, particularly in the midto highfrequency range of wheelrail noise.

To provide maintenance advice regarding a scenario in which floating slab tracks are soaked in water, we established a numerical model of a submerged steel spring floating slab track vibration based on the fluidsolid coupling theory. The vibration reduction of the floating slab track with different accumulation water depths under a running train considering the track, water, and tunnel base was analyzed. The results showed that the water under the floating slab influences the vibration reduction performance. When the depth of the accumulated water was lower than the 1/2 height of the slabside space, the effect on the vertical vibration of the tunnel increased by approximately 5 dB at a peak frequency of 63 Hz. When the water filled with the entire height of the slab side space, the vertical vibration level of the tunnel at its peak frequency of 63 Hz increased to approximately 13.4 dB, an increase of 30.7%. The insertion loss of the tunnel vibration level also increased by approximately 13.36 and 13.67 dB at 63 and 80 Hz, respectively. Therefore, when the height of the water under the floating slab was over the 1/2 height of the slab side space, which means that the vertical vibrations of the slab and tunnel at their peak value frequency were larger than 5 and 10 dB, respectively, than under normal conditions without water, maintenance work to drain away the water should be performed immediately.

This study addresses problems of numerical methods for continuous media, such as the finite difference and finite element methods to simulate the discrete medium characteristics of a sandy cobble stratum. Based on the blockbased discrete element method, a discrete element model is built to simulate the process of shield tunneling through a sandy cobble stratum, and the displacement of joints and deformation of the surrounding rock and liner is studied. A finite difference model, in which a sandy cobble stratum is transformed into an equivalent continuous medium, is built to simulate the process of shield tunneling, and to compare the differences in simulation results between the discrete element model and the finite difference model. The results show that, in the discrete element model, the area at which the positive normal displacement of the joints exceeds 0.1 mm is primarily concentrated at the inverted arch, the area at which the negative normal displacement of the joints exceeds 0.1 mm is located at the hance, and the area at which the shear displacement of the joints exceeds 0.4 mm is primarily concentrated at the inverted arch. The simulation results of the discrete element method are greater than those of the finite difference method with respect to the deformation of the surrounding rock and liner; therefore, utilizing the discrete element method to verify the design of the tunnel and liner is relatively more secure and reasonable.

Focusing on the reuse of tunnel muck, this study aims to prepare tunnel muck from the Suzhou Metro Line 8 into a synchronous grouting material that satisfies the engineering requirements of different geological conditions by adjusting the solidification material compositions through laboratory experiments. In this project, a new doubleline shield tunnel of Metro Line 8 intersects the existing doubleline tunnel of Line 3 at Tangzhuang Station, forming a unique layout with two layers of four tracks. The muckproduced grout used in this project has a consistency value of 113 mm, and the 7and 28day strengths exceed 1 and 2.5 MPa, respectively, satisfying the engineering specifications. The deformation monitoring data show that the muckproduced grout effectively controls the impact of the upper tunnel construction on existing structures. Utilizing shield tunneling muck to prepare synchronous grouting slurry can achieve resource utilization of muck while promoting green construction and reducing construction costs by approximately 750 thousand Yuan per kilometer (double line).

In response to the application problems of eCNY hardware wallets in rail transit gate boarding, business process design and ticketing system transformation methods were adopted to implement eCNY hardware wallets for the Suzhou rail transit gate boarding business. In this paper, first, the basic concept of eCNY hardware wallets is introduced, and the application forms of eCNY hardware wallets in rail transit are clarified. The current business scenario, usage needs, and technical characteristics of eCNY hardware wallets in rail transit and the overall plan for passing through gates and boarding trains with eCNY hardware wallets is determined, and a detailed design is for the registration, entry and exit, ticket processing, and other business processes of eCNY hardware wallets is described. Finally, combined with the current scenario of the Suzhou Rail Transit ticketing system, a specific transformation scheme of the Internet ticketing system and an automatic fare collection system is proposed to achieve the eCNY hardware wallet lockin service. The application of eCNY hardware wallets in Suzhou Rail Transit has a promotional significance for the promotion of eCNY hardware wallets and has a reference value for the application of eCNY in the field of rail transit.