Search Results (430)

To investigate the influence of segmental lining width on ground and tunnel deformation during shield tunneling beneath residential buildings, a numerical analysis model was established using Midas GTS NX based on the engineering context of the Guangzhou Metro Guanggang Xincheng depot tunnel underpassing residential structures. The simulation results were validated through comparison with field monitoring data, and a gray relational analysis was employed to quantitatively assess the sensitivity of various deformation indicators to segment width. The findings indicate that, under the engineering scenario of a shield tunnel crossing beneath residential buildings, the use of 1.2 m-wide segments is more effective in controlling ground settlement and structural deformation of the tunnel compared with 1.5 m-wide segments. The deformation process associated with the 1.2 m segments exhibits a more stable settlement pattern, whereas the 1.5 m segments tend to induce repeated settlement–heave cycles in the surrounding ground, with a potential risk of segmental displacement exceeding warning thresholds. Sensitivity analysis shows that different deformation indicators respond unevenly to changes in segment width. From most to least sensitive, the indicators rank as follows: maximum ground deformation, maximum displacement during the post-excavation stage, and maximum displacement during the excavation stage. The results of this study provide theoretical support and reference for selecting segmental lining width in shield tunnels constructed beneath residential buildings. Full article

Accurate characterization of rail corrugation is essential for the operation and maintenance of urban rail transit. To enhance the representation capability for rail corrugation, this study proposes a sound–vibration feature fusion method based on Laplacian manifold learning. The method constructs a multidimensional feature space using real-world acoustic and vibration signals measured from metro vehicles, introduces a Laplacian manifold structure to capture local geometric relationships among samples, and incorporates inter-class separability into traditional intra-class compactness metrics. Based on this, a comprehensive feature evaluation index L_r is developed to achieve adaptive feature ranking. The final fusion indicator, LWVAF, is generated through weighted feature integration and used for rail corrugation characterization. Validation on in-service metro line data demonstrates that, after rail grinding, LWVAF exhibits a more pronounced reduction and higher sensitivity to changes compared with individual acoustic or vibration features, reliably reflecting improvements in rail corrugation. The results confirm that the proposed method maintains strong robustness and physical interpretability even under small-sample and weak-label conditions, offering a new approach for sound–vibration fusion analysis and corrugation evolution studies. Full article

Automatic Train Operation (ATO) systems are widely deployed in metro networks to improve punctuality, service regularity, and ultimately the sustainability of rail operation. Although eco-driving optimisation has been extensively studied, no previous work has provided a systematic, side-by-side comparison of the two ATO control philosophies most commonly implemented in metro systems worldwide: (i) Type 1, based on speed holding followed by a single terminal coasting at a kilometre point, and (ii) Type 2, which uses speed thresholds to apply either continuous speed holding or iterative coasting–remotoring cycles. These strategies differ fundamentally in their control logic and may lead to distinct operational and energetic behaviours. This paper presents a comprehensive comparison of these two ATO philosophies using a high-fidelity train movement simulator and Pareto-front optimisation via a multi-objective particle swarm algorithm. 40 interstations of a real metro line were evaluated under realistic comfort and operational constraints, and robustness was assessed through sensitivity to three different passenger-load variations (empty train, nominal load and full load). Results show that, once nominal profiles are implemented, Type 1 has up to 5% variability in running times, and Type 2 has up to 20% variability in energy consumption. In conclusion, a new ATO deployment combining both strategies could better balance energy efficiency and timetable robustness in metro operations. Full article

In the metro traction power supply system, the metro acceleration and braking may cause fluctuations of bus voltage, and it is difficult for a single energy storage device to achieve both the proper response speed and energy density. In this article, a novel battery-supercapacitor hybrid energy storage system (HESS) was proposed to realise energy compensation and regulation under complex operating conditions of metros, in order to maintain a stable bus voltage. Using the short station distance working condition of Guangzhou Metro Line 4 as an example, four types of scenarios were designed for acceleration, braking, frequent acceleration-braking and two-metro simultaneous operation. The simulation results show that a single-mode energy storage could not effectively stabilise the bus voltage, while battery-supercapacitor HESS could control bus voltage fluctuation within 2 V. A comparative study on the proposed battery-supercapacitor HESS using a typical Buck-Boost DC/DC converter topology and a different Cuk DC/DC converter topology was carried out. Overall, this article provides a novel battery-supercapacitor HESS to stabilise the metro power system under complex acceleration and braking conditions, and lays the technical foundation for a hybrid energy storage system to be used in actual urban rail transit. Full article

With the continuous expansion of urban metro systems, balancing passenger experience and operational efficiency has become a central concern in contemporary public transportation design. However, most existing metro service studies continue to focus on perceptual comfort or isolated usability tasks and lack an integrated, behavior-centered perspective that accounts for the full travel chain and diverse user groups. This study develops the Bi-directional Service Behavioral Experience Model (BSBEM), which systematically integrates one-way navigation behaviors and interactive operational behaviors within a unified dual-path framework to identify behavioral patterns and experiential disparities across user groups. Based on the People–Touchpoints–Environments–Messages–Services–Time–Emotion (POEMSTI) behavioral observation framework, this study employs a mixed-method approach combining video-based behavioral coding, usability testing, and subjective evaluation. An empirical study conducted at Beidajie Station on Xi’an Metro Line 2 involved three representative passenger groups: high-frequency commuters, urban leisure travelers, and special-care passengers. Multi-source data were collected to capture temporal, spatial, and interactional dynamics throughout the travel process. Results show that high-frequency commuters demonstrate the highest operational fluency, urban leisure travelers exhibit greater visual dependency and exploratory pauses, and special-care passengers are most affected by accessibility and feedback latency. Further analysis reveals a positive correlation between route complexity and interaction delay, highlighting discontinuous information feedback as a key experiential bottleneck. By jointly modeling one-way and interactive behaviors and linking group-specific patterns to concrete metro touchpoints, this research extends behavioral evaluation in metro systems and offers a novel behavior-based perspective along with empirical evidence for inclusive, adaptive, and human-centered service design. Full article

This paper reviews, analyses, and suggests practical mitigation techniques at source for reducing vibration-induced annoyance to occupants in building structures that are built on top of significant railway infrastructure. The dynamic characteristics of vibration caused by wheel-rail interaction at metro train depots are different from those on main-lines and conventional studies. Ground-borne vibration in a building directly above a double-deck railway depot was investigated, focusing on vibration attenuation through rail track design, which is more effective and economic compared to treatments at receivers or along prorogation paths. A 2.5-Dimensional finite element model was established to simulate vibration transmission using different combinations of track-forms. Source contribution under different train running conditions has been evaluated by computing vibration levels along the main transmission path. Vibration levels at representative positions in the building rooms have been predicted using the numerical model and have been compared against site measurements at the corresponding locations after the completion of the construction of the depot and buildings. It was found that the 2.5D FE model enables a reasonable prediction of ground-borne vibration from the metro depot, and that by appropriate design of the track-form, a good level of vibration attenuation can be achieved in an economical way. Full article

Currently, unreinforced steel fiber-reinforced concrete (USFRC) has not been widely adopted in underground engineering within China. However, extensive research has demonstrated that incorporating steel fibers can effectively enhance the mechanical properties of concrete, such as tensile strength, shear strength, residual flexural tensile strength, and also improve its durability. This study, based on the Qiandong experimental section of Dalian Metro Line 4, aims to investigate the failure modes, bearing capacity, and calculation methods for reinforced concrete (RC) and USFRC lining segment joints under compression-bending loading. The objective is to provide a reference for the application of USFRC lining segments in domestic underground engineering. The main conclusions are as follows: (1) The primary failure mode of RC segment joints is large-area crushing of concrete on the outer curved surface, with tensile crack widths on the inner curved surface less than 0.20 mm. The failure mode of USFRC segment joints is characterized by a 2.50 mm wide tensile crack below the loading point. (2) The bolt strain at failure for RC segment joints is approximately twice that of USFRC joints, with both reaching the yield strength and entering the plastic deformation stage. The bolt stress versus bending moment curve exhibits two distinct growth stages. USFRC can effectively control bolt deformation and stress, thereby enhancing bearing capacity. (3) The joint rotation angle versus bending moment curve follows a bilinear model. Under identical bending moments, the rotation angle of RC segment joints is significantly larger than that of USFRC joints. In the two stages, the rotational stiffness of USFRC joints is 367.13% and 763.82% of that of RC joints, respectively. (4) Bolts do not influence the bearing capacity of the segment joints. Existing calculation models in current design codes can accurately predict the ultimate bearing capacity of both RC and USFRC segment joints, demonstrating high prediction accuracy. Full article

To reduce downtime of the Tunnel Boring Machine and improve construction efficiency of subway tunnels, the tunnel–station synchronous construction method was implemented in the Qingdao metro. In this method, the TBM advanced continuously through the station, while the upper station was excavated in stages using the primary support arch covering technique. Focusing on a construction scheme with low-grade temporary segments, this study develops a three-dimensional numerical model to investigate the mechanical response of shield lining during the simultaneous construction of a subway station and tunnel. The Mohr–Coulomb model and the Elastic model were employed to represent the mechanical behavior of the surrounding rock and support structure, respectively. The deformation, bending moment, axial force, and residual bearing capacity coefficients of the shield lining were systematically examined across six distinct construction stages. The results showed that asymmetric gradual unloading of the surrounding rock at the arch part caused the vertical displacement of the shield lining to be predominantly upward, with a maximum heave of 1.51 mm. Horizontal displacement exhibited significant asymmetry. During station arch excavation, asymmetric unloading led to an increase and clockwise shift in the bending moments of the shield lining. The axial forces transitioned from compression to tension at specific locations (40° and 240°), whereas the removal of temporary supports had only a minor influence. The maximum tensile stress of the shield lining increased by 3.35 times in Stage III and reached 0.69 MPa in Stage V, representing a 1.65-fold increase compared to the previous stage. Although the residual bearing capacity coefficient generally satisfied safety requirements throughout the construction process, it decreased to a minimum of 0.88 in Stage V, a 7% reduction relative to Stage IV, necessitating close monitoring. This study not only confirmed the safety of using temporary segments made of lower-grade concrete (C30) in tunnel–station synchronous construction but also provided valuable insights for optimizing construction schemes and controlling key risks, such as structural deformation, in similarly complex urban environments. Full article

The metro system is a key driver of urban land use development; however, its spatiotemporal impact mechanisms remain insufficiently understood. This study investigates the effects of metro development on land use types and development intensity in Wuhan, China, from 2014 to 2019, and employs a Geographically and Temporally Weighted Regression (GTWR) model to capture the spatiotemporal heterogeneity of these impacts. Results show that metro construction significantly promotes land use transformation along metro lines, especially from non-construction land to residential and commercial uses, while also increasing development intensity. GTWR analysis further reveals that metro network characteristics, station attributes, and built environment features surrounding stations strongly influence land development. These impacts exhibit pronounced spatiotemporal heterogeneity, becoming more pronounced over time as the metro network extends into suburban areas. The findings provide valuable insights for urban and transportation planners, supporting the formulation of strategies for integrated land use development and metro network expansion. Full article

As laboratory experiments evaluating soil strata conditioning schemes for earth pressure balance shield (EPBS) tunneling are limited by the size of the test equipment, large pebbles and boulders are typically replaced by an equal mass of smaller pebbles (≦40 mm), resulting in behaviors that differ significantly from those of the in situ soil and causing the obtained conditioning scheme to perform poorly during actual tunnel construction. This study applied a laboratory-obtained conditioning scheme during EPBS tunneling in the boulder- and pebble-rich soil strata between Yushuzhuang and Wanpingcheng on Beijing Metro Line 16 to determine the optimal soil conditioning scheme using the upper soil chamber pressure, cutterhead torque, tunneling speed, and total thrust tunneling parameters as evaluation indices. The optimized soil conditioning scheme provided a better soil conditioning effect than the laboratory-obtained scheme and confirmed that the considered parameters reflected the soil conditioning effects. Finally, the correlations between these three soil conditioning factors and the four tunneling parameters were analyzed using a full factorial experimental design to obtain contour plots of their quantitative relationships for use in similar tunneling projects. Full article

Subway stations are enclosed spaces with high passenger density and complex evacuation conditions. Fires in such environments can escalate rapidly and cause severe consequences. This study proposes a dynamic risk assessment model grounded in dual symmetries. The first symmetry is a balanced “Human–Machine–Environment–Management” analytical structure. The second is a coherent model transformation from a Fault Tree (FT) to a Bayesian Network (BN). Shuanggang Station on Nanchang Metro Line 1 serves as a case study. This work establishes a comprehensive evaluation system based on 4 first-level indicators of man–machine–environment–management, 9 secondary indicators, and 27 tertiary indicators. FT analysis identified 117 minimal cuts and 14 minimal paths, pinpointing core risk nodes such as flammable materials and oxidizers, electrical equipment overheating, and fire management deficiencies. The model was then symmetrically converted into a BN using GeNle Academic 4.1 software to support dynamic probability inference. The results show that prevention measures at Shuanggang Station reduce the fire occurrence probability from 0.000249 to 0.00007 (a 71.9% reduction). The probability importance of rescue escape routes is 0.00223. This indicates that the accessibility of rescue routes constitutes a highly sensitive hazard. The symmetric framework and modeling approach offer a scientific basis for targeted fire prevention, control, and evacuation management in the Nanchang Metro and similar stations. The findings support improvements in the safety and resilience of metro operations. Full article

With the rapid expansion of urban transportation networks, new metro tunnels frequently cut through existing structures’ diaphragm walls by using the shield machine. Such intrusions induce dynamic disturbances that pose significant risks to adjacent structures. This study employs Suzhou Metro Line 8 as a case study to evaluate the safety of existing metro stations during shield tunneling, specifically examining deformation characteristics induced by varying tunneling parameters. A three-dimensional numerical model is developed to assess structural responses, with simulation accuracy rigorously validated against field measurements. Results reveal that the transverse influence zone of the base slab extends approximately 2.5 times the tunnel diameter. Diaphragm wall exhibits horizontal deformation opposite the tunneling direction, while the maximum lateral deformation of adjacent station walls reaches 2.49 mm. Concurrently, a slight uplift manifests at the base slab center with a peak value of 2.54 mm. All obtained structural deformations remain well below the permission value of 5 mm, with observed maxima constituting only 50% of this safety threshold. This substantial deformation margin significantly mitigates construction hazards, promoting the sustainable development of underground space. Full article

A critical task in infrastructure security is to model user traffic in transportation systems to alert whenever anomalous behavior is observed. Discerning those abnormal samples is possible by auditing the available data, which then enables proper policy making to guarantee fair tariffs and the design of strategies to tackle problems such as passenger congestion. In this paper, we present an offline cybersecurity approach for the multimodal modeling of user traffic for the Colombian metro. To identify the anomalies, we design custom Deep Autoencoders based on the embeddings produced by the Self-Supervised Learning TabNet architecture. Additionally, we provide explainability through a SHAP-based component and the analysis of external image data using LLaVA as the selected Large Multimodal Model. The results indicate that most problems that occur on one metro line also affect the other, demonstrating the interconnectivity of the metro system, a crucial aspect that motivates the coordinated emergency response to improve the passenger travel experience. Although the detected problems might already have been identified and reported on social media, the transparency provided helps create confidence when an abnormality is observed, and in case there is no backup information on our official external data sources, it represents an alert to examine it more deeply, becoming an intelligent assessment tool for the metro. This article also sheds light on the potential of the publicly available dataset used and the importance of expanding its existing variables and information. Full article

The opening degree of longitudinal joints in the segmental lining of cross-passages in soft soil strata directly affects structural safety during tunnel construction. This study utilizes field monitoring data from the F-capping segment of Ring 30 in the Guangzhou–Nanzhou Intercity Railway Connecting Tunnel. Employing multivariate linear regression analysis, it investigates the variation patterns in longitudinal joint opening in connecting tunnel segments under changes in earth pressure, water pressure, axial force, and reinforcement stress. The fitted results for joint opening are compared with field monitoring data, demonstrating good agreement. The results indicate that axial force and reinforcement stress exert minimal influence on longitudinal joint opening in soft soil sections. Conversely, hydrostatic pressure and earth pressure exhibit moderate linear correlations with joint opening: opening increases with rising hydrostatic pressure and decreases with increasing earth pressure. These findings, based on short-term monitoring data from a single ring during construction, provide preliminary theoretical and empirical support for understanding joint behavior in site-specific soft soil conditions. Further validation is required for generalized early warning systems. Full article

This study addresses the joint optimization of full-length and short-turning operations for the Nanchang Metro Airport Line, aiming to balance operational efficiency and passenger service quality. A novel mathematical model is proposed, which integrates train schedule design, capacity allocation, and passenger flow assignment into a linear programming framework. The model features three key innovations: (1) precise calculation of passenger waiting times under strict capacity constraints by incorporating dynamic passenger flow distribution and train occupancy thresholds; (2) implicit treatment of train numbers as decision variables, enabling flexible adjustments to service frequency based on time-varying demand patterns; and (3) a linear formulation for direct optimal solution computation, avoiding the complexity of nonlinear constraints through variable substitution and constraint relaxation. The model is validated through a case study of the Nanchang Metro Line 1 (Airport Line), where passenger demand is derived from historical data and flight schedules. Numerical experiments demonstrate that the optimized strategy reduces the number of full-length trains by 53%, achieves a 22% power cost saving, and decreases the waiting time for all passengers by 3.4%. The relevant findings and recommendations can offer valuable guidance to metro companies in making operational decisions related to the full-length and short-turning service plans and schedules. Full article