To address the technical challenge of balancing pile foundation treatment efficiency and structural safety during shield tunneling beneath urban viaducts, this study focuses on key issues of shield cutting pile groups in mudstone strata, taking the Sichuan Normal University-Jiaozi Overpass section of Chengdu Rail Transit Line 13 as the engineering background. Through innovative cutter selection and construction control technology, a comprehensive shield pile-cutting solution that balances construction efficiency and structural safety has been developed. Combining theoretical analysis with numerical simulation, parameters such as the front angle, blade angle, and blade width of shell cutters were optimized. The research results indicate: ① A composite cutterhead with 6 panels +6 spokes, equipped with double-edged shell cutters featuring -45° front angle (zero back angle), 90° blade angle, and 10 mm blade width, significantly improves shield pile-cutting effectiveness; ② The optimized tool arrangement combining disc cutters, scrapers, shell cutters, and pre-cutters, along with shield machine system improvements and construction control measures, achieves optimal pile-cutting performance; ③ Field monitoring shows maximum pile-top settlement of 2.81 mm and post-stabilization settlement of 1.75 mm, with 76.3% of discharged reinforcement bars shorter than 750 mm and 70.1% showing clean-cut fractures, demonstrating reasonable cutter layout that effectively severs most reinforcement while minimally impacting pile-top settlement. These findings provide valuable references for shield pile-cutting methods in complex strata.

A new ballasted track rail fastening system has been developed to address the problems of environmental pollution, harm to the health of construction personnel, low efficiency, screw spike misalignment, and difficulty in ensuring anchoring quality in the construction of prestressed concrete sleeper fasteners for traditional ballasted track beds using sulfur cement mortar anchoring. The system incorporates an embedded composite sleeve within the sleeper, eliminating on-site sulfur-mortar anchoring or embedded nylon sleeve solutions. This yields a more environmentally friendly and efficient process; its simple structural design and easy operation enhance installation workmanship, reduce environmental burden, improve installation quality and productivity, and extend service life. Under the background of the increasing emphasis on green construction and high-quality development in domestic rail transit construction, this technology has a very broad market prospect.

To mitigate the risks of device impersonation and information eavesdropping faced by urban rail transit safety equipment in open network environments, this paper proposes a system scheme for lightweight Public Key Infrastructure (PKI) based on domestic cryptographic algorithm (SM algorithm), which takes into account the certificate issuance scheme for administrative management needs. First, based on the characteristics of urban rail transit, a hierarchical X.509 certificate system signed with the SM2 algorithm was designed. Then, leveraging the public key information embedded in the certificates, a three-way handshake protocol was proposed to achieve session key negotiation in a fully open network environment. Finally, communication procedures for intra-domain and inter-domain device handshakes were constructed, and their performance (efficiency) was analyzed. The results show that the proposed system still ensures point-to-point encrypted communication between devices even if all inter-device communication data are fully exposed. The device-to-device key negotiation takes approximately 214.5 ms under average conditions and about 2557.5 ms in the worst case; both values are far below the duration of the communication overlap zone when a train transitions between regional control centers, thereby ensuring acceptable efficiency.

In order to study the necessity of setting up piston ventilation ducts in metros in China's severe cold regions, this article selects typical station public areas and section tunnels of the operating Shenyang Metro Lines 1 and 9, and tests their temperature, carbon dioxide concentration, and inhalable particulate matter concentration under open ventilation operation in the hottest month and closed ventilation operation in the coldest month; utilizing temperature as an indicator of the thermal environment, carbon dioxide concentration and inhalable particulate matter concentration as a measure of air quality, this research quantitatively analyzes the actual environmental control effect of the open ventilation system of the full-height non-enclosed platform doors in operating Shenyang Metro lines on the typical stations public areas and section tunnels. The findings suggest that the piston ventilation volume formed by the open ventilation system of the full-height non-enclosed platform doors in the Shenyang Metro within the section tunnels has exceeded the amount required for temperature control, indicating that the actual regulating capacity of the piston ventilation ducts on the thermal environment of the section tunnels is relatively weak; after closing the piston ventilation duct, the thermal environment and air quality can still meet the design specifications; for future metro lines in Shenyang, it may be advisable to eliminate the piston ventilation ducts (shafts) as an optimization design scheme of the piston ventilation system; the elimination of piston ventilation ducts (shafts) has no impact on the safety of ventilation mode in station public areas and tunnel sections under both normal and emergency operating conditions. The research results in this paper can serve as a reference for the optimal design of piston ventilation systems in metros in other cities located in severe cold regions in China.

To address the difficulty of directly monitoring fatigue damage in bogie-end suspension components caused by vibration during long-term service, this study takes a track inspection device as an example to analyze its fatigue failure mechanism and proposes an indirect fatigue stress monitoring scheme based on deep learning. Hazardous measurement points were identified via finite element analysis, and data on vibration acceleration at the frame end and component stress were collected through field line tests. Three temporal regression models (RNN, LSTM, and TCN) were constructed to establish the mapping relationship between acceleration loads at the frame end and component stress. The attention mechanism was introduced to optimize model performance. Experimental results demonstrate that all three models effectively predict stress, with the LSTM model incorporating the attention mechanism (LSTM-Att) achieving the highest prediction accuracy. Validation on six stress measurement points of the track inspection device confirmed that LSTM-Att exhibits excellent predictive performance in both the time and frequency domains. This proves the effectiveness of the proposed method and offers a novel approach for monitoring fatigue damage in frame end-suspended components.

In response to issues such as complex wiring in traditional platform screen door control systems, difficulties in daily maintenance of relays, challenges in troubleshooting, and cumbersome intermediate transmission links in interactions with signaling systems, this paper proposes a platform screen door controller (PSDC) solution. This solution employs SIL4-level safety technology based on domestically developed hardware and software, along with a “fail-safe” all-electronic single-board technology, achieving a fully electronic design for the platform screen door controller. By integrating computer and network technologies, the solution realizes the integration and digitalization of interfaces between the signaling system and the platform screen door system. Comparative analysis between the traditional platform screen door control system and the proposed solution in terms of system architecture, control links, and engineering implementation reveals that the fully electronic design of the platform screen door controller features a simpler overall architecture, real-time fault detection and alarm capabilities, and eliminates inherent safety hazards associated with relay-based control circuits, significantly enhancing system safety, reliability, and availability. The proposed solution not only simplifies the debugging process for the coordinated operation of train doors and platform screen doors but also significantly reduces the information exchange time for onboard train door opening/closing upon station arrival by approximately 4 seconds, thereby improving the operational efficiency and headway of the entire line. The research findings can serve as a reference for the development of multi-dimensional integration in urban rail transit.

The robustness of transportation networks under emergency events is a key factor in assessing the resilience of urban public transportation systems. To study the emergency response capabilities and resilience performance of complex urban transportation systems during emergency events, this study takes the central urban area of Chongqing as the study region and constructs a bus-metro multilayer transportation network model based on complex network theory to evaluate the robustness and emergency response capabilities of the urban transportation system under different shock modes. Through simulation analysis, the study delves into the catastrophic failure mechanisms and resilience trends of the two-layer network, and investigates the emergency coordination capabilities of metro and bus lines. In response to the vulnerability of single networks in current urban transportation systems during emergencies, an improved load-capacity model is proposed and used to analyze the network resilience under different attack modes. The study results show that: (1) The two-layer network exhibits a slower decline in network efficiency under both shock modes, with its redundancy and multi-path characteristics effectively mitigating the collapse process; (2) In the cascading failure process, the robustness of the two-layer network is consistently superior to that of single bus and subway networks, and the cascading failure caused by the failure of important stations has a more significant impact on network connectivity and efficiency; (3) The two-layer network is more effective in maintaining network connectivity and operational efficiency, especially when facing unexpected events, demonstrating stronger adaptive capacity and robustness. It can effectively share the load, alleviate congestion in single networks, and improve emergency handling efficiency.

To address the problems of unclear functions, unclear positioning, and insufficient integration with rail transit after rail networks are formed in major cities, this study reconstructs an integrated public transportation network system dominated by rail transit from a multi-dimensional perspective of “3-dimensional system, 2-dimensional line network, and 1-dimensional line”. The study analyzes the implementation strategy of rail-bus “dual network” integration in detail, proposes a hierarchical and step-by-step optimization method and implementation path for the “express-trunk-branch” bus network, and applies theoretical methods to the reform of Chengdu's public transportation network system. The research results indicate that the integration and coordination of Chengdu's public transportation networks and the rail-bus “dual network” integration have been significantly improved. This provides valuable reference for the systematic construction of public transportation networks and the optimization of hierarchical bus networks in other large cities.

This study addresses the issues of energy consumption and greenhouse gas emissions caused by the rapid development of urban rail transit and proposes a budget quota-based carbon emission accounting method for rail transit. By integrating carbon emission intensity and economic intensity indicators, a multi-level carbon emission analysis framework—comprising “station-section-line”—is constructed. Using the Fuzhou Metro Line 6 Phase I and its western extension project as a case study, the carbon emission characteristics during the construction phase of rail transit are quantitatively analyzed. The results indicate that the production of construction materials is the primary source of carbon emissions, accounting for 50% to 79% of total emissions, with steel reinforcement, concrete, and cement being the major contributing factors. At the station level, the carbon emission intensity per unit area ranges from 1.67 to 3.40 tCO₂ e/m², influenced by station scale and structural design; the economic intensity ranges from 1.54 to 3.40 tCO₂ e per ten thousand yuan, mainly affected by the low-carbon level of rail transit technologies. At the section level, carbon emission intensity varies significantly with different construction methods. Sections using the cut-and-cover method exhibit higher carbon emissions, with the maximum reaching 36.5 tCO₂ e per double track meter, primarily due to higher demand for steel and concrete. This study provides a scientific basis for low-carbon construction throughout the lifecycle of urban rail transit, and holds significant theoretical and practical value for promoting the green and low-carbon transformation of the rail transit sector.

In response to regulatory requirements for safety evacuation in metro station, based on the location of emergency, this paper summarizes evacuation path and evacuation volume under different conditions. Discussing the method to calculating evacuation time which is in the code for safety evacuation, the view that safety evacuation simulation should be conducted is proposed. And the four key factors affecting the safety evacuation time in design stage are identified in this paper, mainly including evacuation volume, capacity of evacuation facilities, lifting height from the platform to the concourse or other safety zone, and distribution of evacuation facilities on the platform. By comparing the impact of escalator which is in the opposite direction on evacuation capacity, the rationality of using reverse escalator under the emergency evacuation condition are discussed. Considering on practical work experience, it is suggested that the timing of safety evacuation simulation should be advanced to the preliminary design stage.