Quality defects in segment assembly, such as misalignment and ellipse deformation, often occur during shieldtunneling excavation. Construction quality defects threaten tunnel stability and safety. To ensure the safe construction and service of shield tunnels, a quality assessment of the shield segment assembly is necessary during construction. Limited by manual detection methods, traditional sitequality assessment is challenged by low efficiency, limited accuracy, and missing data. Three dimensional laser scanning was introduced to collect pointcloud data during the assembly of the shieldsegment lining. The ellipticity and misalignment values of the shield segments were calculated by the long and shortaxis algorithms and the improved slope segmentation algorithms. Based on the theory of centerpoint extraction of ringseam data, a method for extracting the central axis and center point of a tunnel through ringsegment data fitting was proposed for high precision, efficiency, and automation to detect shieldsegment assembly quality. A shieldtunnel project was conducted to demonstrate and validate the proposed method. The results show that the proposed method can efficiently and automatically assess the assembly quality of shieldconstruction segments.

The maximum operating speed of urban rail expresses is 160 km/h. As the main technical parameters of the gauge in the current national standards do not cover this speed, this study uses theoretical analysis and dynamic simulation methods to research the gauge system and calculation methods. The calculation formulas in the Standard of Metro Gauges (CJJ 962003) were adjusted to be suitable for the 160km/h express project. The optimal structure gauges of the station, tunnel, and bridge were formulated in combination with the express project characteristics based on research on the basic gauge parameters. 1) Compared with the stopping condition, when the train passed the station at 100 km/h, the distance between the station platform and the central line of the track was 1,600 mm. 2) The size of the circular tunnel section was determined by the space requirement for equipment layout in the urban rail express project. When the flexible overhead contact system was used, the optimal tunnel diameter was 7.5 m (the gauge diameter was 7.2 m). When the rigid overhead contact system was used, the optimal tunnel diameter was 7.1 m (the gauge diameter was 6.8 m).

Current solutions for enhancing the efficiency of existing urban rail transit lines are limited. As a pioneering initiative, the concept of running express/local trains on these lines presents a versatile solution for Shighquality development scenarios. After systematically reviewing the methods for running express/local trains on existing lines, this paper introduces four distinct strategies tailored to the unique features and operational needs of different lines: employing extended intervals for rapid trains, implementing alternate stationskipping for accelerated service, utilizing malfunctioned train stop lines for express/local runs, and operating partialroute shuttles for express/local trains. Drawing from domestic and international case studies, this research delves into the operating principles, advantages, disadvantages, and operational requirements of the aforementioned methods. Additionally, the necessary modifications for implementing express/local train services on existing lines are discussed.

To explore the optimal scheme for the construction and upgrading of the big data platform in the urban rail transit industry, this study takes the urban rail big data platform as the research object. Our study starts from the development process of the urban rail big data platform, sorts out the three stages of the development of the urban rail big data platform and analyzes the technology and advantages and disadvantages of the big data platform at each stage. Then it focuses on summarizing the advantages of "Data lake and Warehouse integration, stream processing and batch processing integration, OLTP+OLAP, multiple loads" and other advantages of the "Data Lakehouse" big data technology in the current stage, and studies the key points of the architecture upgrade and transformation design of the big data platform based on this technology. The technology was verified in the upgradation and transformation of the big data platform of the Beijing Metro Data Center. The application shows that the "Data lakehouse" big data platform technology combines the advantages of low cost of data lake and high performance of data warehouse, solves the shortcomings of the original big data platform in performance, capacity and multipurpose support, and provides new solutions for the construction and upgradation of big data platforms in the urban rail industry.

To evaluate the vibration reduction effect of urban express, similar sections with essentially the same line conditions were studied. Different vibration reduction measures and corresponding common overall track bed sections were tested onsite to study the vibration reduction effect of urban express vibration reduction measures. Through the time domain, frequency domain, and onethird octave analysis of the measured data, the vibration reduction measures and maximum Zvibration level (VLZmax) of the ordinary section of the tunnel wall were obtained, and the vibration reduction effects of different vibration reduction measures were compared. The vibration acceleration of the tunnel wall at the measuring point and the ground vibration were analyzed in onethird of an octave to obtain the propagation attenuation of the vibration. The results show that the three vibration reduction measures reduced vibration. The vibration reduction of the doublelayer nonlinear vibration reduction fastener was 7.3 dB; the vibration reduction was 16.2 dB for the vibration damping pad floating plate and 19.7 dB for the steel spring floating plate.

This study comprehensively summarizes the testing scheme and results of a laddersleeper ballastless track in urban rapid rail transit for safety, stability, and vibration reduction performance compared with an ordinary ballasted track at a maximum speed of 220 km/h on the National Railway Test Center Circular Line in 2023. The test used eight CRH380AJ comprehensive inspection units, including the safety and stability of the wheelset derailment coefficient, wheel load reduction rate, wheelrail lateral force, vertical and lateral dynamic displacement indicators of the rail and sleeper, vertical and lateral vibration characteristics of the rail, and vibration reduction performance of the roadbed surface at a distance of 3.5 m from the centerline of the line. The test results for these indices were lower than the limits of the corresponding standards and close to those for the existing ballasted track. The test results show that the safety, stability, and wheelrail vibration characteristics of the laddersleeper ballastless track in urban rapid rail transit can satisfy the requirements of the line at a speed of 220 km/h. According to different weighting methods, the average vibration reduction of the laddersleeper ballastless track compared with an ordinary ballasted track in urban rapid rail transit can reach 3.35.1 dB and 4.46.8 dB. The test results provide a reference for urban rapid rail transit and intercity railway track vibration reduction technologies.

Addressing the critical issue of subway structure leakage in Beijing due to rising groundwater levels, this study focuses on the development of an effective management framework. The work presents a comprehensive prevention and control technology system tailored for the Beijing subway, encompassing risk identification, assessment, and mitigation strategies. The investigation begins with pinpointing the diverse factors that contribute to leakage and proceeds to evaluate the risks through both qualitative and quantitative approaches, which apply to different segments and stations within the subway system. Risk levels ranging from A through D have been devised to facilitate targeted emergency and routine leakage management protocols. The resultant strategies accommodate both urgent responses and standard leakage rectification processes. The findings of this research aim to serve as a theoretical and technical groundwork for the management of similar urban subway structures.

Renovating existing lines is a key longterm task for achieving highquality and sustainable development of urban rail transit in China. Technical standards are essential for initiating, designing, and implementing renovation projects. This paper reviews the current technical standard system for urban rail transit and examines the suitability of existing standards for each stage of the renovation process. To address the issues of incomplete coverage, low applicability, and poor relevance of existing standards, we propose two approaches and schemes for developing a new technical standard system for renovating urban rail transit lines, along with the principles for constructing and formulating the standards. We focus on the technical standards for renovation, including the requirements for renovation determination, design, construction, acceptance, safety assessment, and postevaluation.

Groundsurface deformation characteristics caused by jacked rectangular pipes differ from those caused by jacked circular pipes or shield tunnels. The groundsettlement characteristics during the construction of a shallowburied rectangular jacked pipe and its impact on the existing shield tunnel below the jacked pipe were clarified. Using the onsite monitoring results from jacked rectangular pipe construction, the deformation patterns of the ground surface during jacked rectangular pipe construction and the deformation of the existing shield tunnel below the jacked pipe were analyzed. The traditional Peck formula was applied to circular pipejacking and circular shield tunnels; the improved Peck formula was used to describe the surface deformation caused by rectangular pipejacking. The surface deformation, pipeline deformation, and settlement pattern of the submerged tunnel caused by jacked pipes were analyzed based on field monitoring. The results show that the improved Peck formula can describe surface deformation caused by jacked rectangular pipes more accurately than the traditional Peck formula. The settlement patterns of the surface and pipeline caused by jacked pipes were consistent; however, there were differences in the settlement patterns of the underlying tunnel.

Passenger flow forecasting for the initial operation stage of a new rail transit line is fundamental for operational safety assessment and organizational preparation. This study analyzes the characteristics of forecasting work in terms of the forecasting period, research objects, basic modeling data, and forecasting models. The technical difficulties in carrying out such forecasting work are also summarized. Considering the characteristics and difficulties of forecasting, this study introduces a new forecasting framework, and the key procedures in the framework are then explained, including data collection, traffic surveys, analysis of the operational characteristics of urban transport, travel demand forecasting from macroscopic and intermediate perspectives, forecasting evaluation, and sensitivity analysis. Finally, the study also discusses main research points of forecasting work with respect to network passenger flow indices, the impact of a new line on the existing network, and the necessary concerns of essential stations. It is suggested that the forecasting work should focus on the current state of urban systems. Thus, it is essential to collect and understand the current information on urban traffic and the city itself and to analyze shortterm development trends. Because the macroscopic demand analysis models may have lower accuracy, it is also necessary to construct a thematic model for rail transit systems based on urban transport macroscopic demand analysis by conducting traffic surveys. The results of this study can provide references for technical methods and research content of passenger flow forecasting in the initial operation stage.