Tunnel Structure Research Articles

Prediction of BLEVE-induced response of road tunnel using Transformer network with modified self-attention (SAMT)

Road tunnels might be exposed to Boiling Liquid Expansion Vapor Explosion (BLEVE) due to the transportation of liquified gas tankers passing through road tunnels. An efficient and accurate prediction of the response of road tunnels under internal BLEVEs can facilitate the reliable BLEVE-resistant design and risk assessment of road tunnels. This study introduces an advanced deep-learning model that employs a Transformer-based architecture with a modified self-attention mechanism, termed as Self-Attention Modified Transformer (SAMT), to predict BLEVE-induced support rotation of tunnel structure, which is a common criterion in assessing reinforced concrete structure damage to blast loads. Unlike the Transformer with the traditional self-attention mechanism, the proposed SAMT effectively aggregates global information across all variables while mitigating undue dependencies among uncorrelated variables. Consequently, the proposed SAMT is better suited for processing tabular data with uncorrelated variables. The feasibility and advantages of the proposed SAMT are verified by extensive data generated using calibrated numerical models of box-shaped road tunnels subjected to internal BLEVEs. By comparing the performance of the proposed SAMT with the non-modified Transformer network (FT-Transformer) as well as two other typical deep learning networks, i.e., Multi-layer Perceptron (MLP) and Residual Network (ResNet), it is found that the SAMT offers higher prediction accuracy and robustness than the other three models in predicting BLEVE-induced support rotations of box-shaped road tunnels. The study demonstrates that the proposed SAMT is an effective tool for the prediction of BLEVE-induced support rotations of road tunnels.

Discovery, characterization and mechanism of a Microbacterium esterase for key d-biotin chiral intermediate synthesis

Esterases are crucial biocatalysts in chiral compound synthesis. Herein, a novel esterase EstSIT01 belonging to family V was identified from Microbacterium chocolatum SIT101 through genome mining and phylogenetic analysis. EstSIT01 demonstrated remarkable efficiency in asymmetrically hydrolyzing meso-dimethyl ester [Dimethyl cis-1,3-Dibenzyl-2-imidazolidine-4,5-dicarboxyate], producing over 99% yield and 99% enantiomeric excess (e.e.) for (4S, 5R)-monomethyl ester, a crucial chiral intermediate during the synthesis of d-biotin. Notably, the recombinant E. coli expressing EstSIT01 exhibited over 40-fold higher activity than that of the wild strain. EstSIT01 displays a preference for short-chain p-NP esters. The optimal temperature and pH were 45 °C and 10.0, with Km and kcat values of 0.147 mmol/L and 5.808 s− 1, respectively. Molecular docking and MD simulations suggest that the high stereoselectivity for meso-diester may attribute to the narrow entrance tunnel and unique binding pocket structure. Collectively, EstSIT01 holds great potential for preparing chiral carboxylic acids and esters.

Multi-mode fiber Bragg grating for simultaneous detection of strain, torsion and temperature

In this study, a fiber Bragg grating sensor utilizing multi-mode optical fiber (MM-FBG) is proposed. This sensor can simultaneously detect both temperature and torsion, or strain and torsion. Unlike single-mode fiber, the multiple modes of multi-mode fiber can generate several reflection peaks within the FBG area, increasing data capacity and enabling multi-parameter detection. By monitoring the center wavelength and reflection intensity of the MM-FBG reflection peaks, the sensor can detect temperature, torsion, and strain simultaneously. This approach simplifies parameter characterization compared to traditional methods, reducing signal interference and enhancing the clarity of experimental results. Experimental findings demonstrate that the MM-FBG sensor structure exhibits maximum sensitivities of 0.571 dBm/°/cm for torsion, 12 pm/°C for temperature, and 0.7411 pm/με for strain. Therefore, the fiber sensor proposed in this study shows great potential for monitoring bridge and tunnel structures and for civil engineering applications.

Enhanced pseudocapacitive properties of cobalt-doped manganese oxide electrode utilizing magnesium sulfate electrolyte for supercapacitors

This paper investigates the enhanced pseudocapacitive properties of cobalt-doped manganese oxide (Co-doped MnO2) electrode in magnesium sulfate (MgSO4) electrolyte for supercapacitor applications. Co-doped MnO2 was synthesized on nickel foam through a controlled hydrothermal process and specific heat treatment parameters. This resulted in the transformation into α-MnO2 with a 2 × 2 tunnel structure. Morphological investigation illustrates the presence of a hierarchical micro-flower structure with a substantial surface area and mesoporous distribution. The specific surface area of the Co-doped MnO2 electrode significantly increased to 158 m2 g−1, compared to the pristine (bare MnO2) electrode (80 m2 g−1). Electrochemical analyses revealed a specific capacitance of 527 F g−1 at 1 A g−1 in MgSO4 (1 M), showcasing a 1.6 times improvement over Na2SO4 (1 M). The unique structure of the Co-doped MnO2, combined with magnesium ions as efficient electron donors, contributes to superior charge-storage, making it a promising candidate for high-performance supercapacitors. Comprehensive characterizations, such as XRD, XPS, BET, SEM, GCD, and EIS, confirm the advantageous electrochemical performance and durability of the Co-doped MnO2 electrode in MgSO4 electrolyte.

Assessment of Tunnel Lining Stability through Integrated Monitoring of Fiber Bragg Grating Strain and Structural Deformation.

Tunnel excavation induces the stress redistribution of the surrounding rock. Structural cracks may develop in the secondary lining due to this stress redistribution and bias pressure, consequently affecting the overall construction safety of the tunnel. This paper aims to achieve real-time monitoring of the excavation stability of the lining structure by integrating two monitoring technologies: structural deformation monitoring and fiber grating strain monitoring. Additionally, it proposes a method to simultaneously measure the thermal strain and applied stress-strain of the structure. By analyzing the displacement and deformation of the lining structure, its stability can be preliminarily evaluated in the short term. To achieve long-term real-time monitoring and a more accurate assessment of the tunnel structure's stability, the paper introduces fiber Bragg grating (FBG) strain sensor monitoring technology. First, based on the geological stratigraphy information obtained from the exploration, a simulation model of the tunnel under different section bias angles is established. The displacement and stress concentration areas of the lining structure are then analyzed to optimize the sensor deployment array and provide a theoretical basis for the sensor arrangement. FBG strain sensors are installed on the surface of the structure to measure thermal strain and loading stress-strain, whereas FBG temperature sensors measure local temperature. The findings indicate that following tunnel excavation, the maximum daily strain differences at K107+043 and K107+240 were 126.87 µε and 209.38 µε, respectively. After a period of rock disturbance, the average daily strain differences due to applied stress-strain were 16.8 µε and 12.65 µε, respectively. The thermal strain was close to the daily strain difference. Therefore, after the rock disturbance subsided, the strain fluctuations in the lining structure were mainly caused by local temperature changes, and the surrounding rock tended to stabilize. This offers a viable method for evaluating structural stability post-tunnel excavation.

Interplay between magnetic gap and quasi-particle lifetime in topological insulator ferromagnet/f-wave superconductor junctions

Using the modified Blonder–Tinkham–Klapwijk (BTK) theory, the interplay between the lifetime of quasi particles and the magnetic gap in a topological insulator-based ferromagnet/f-wave superconductor (TI-based FM/f–wave SC) tunnel structure is theoretically studied. Two symmetries of f 1 and f 2 waves are considered for superconducting pairing states. The results indicate that reducing the finite quasi-particle lifetime will induce a transformation of energy-gap peaks into a zero-bias peak in tunneling conductance spectrum, as well as a transformation of energy-gap dips into a zero-bias dip in shot noise spectrum, ultimately resulting in the smoothing of the zero-bias conductance peak and the zero-bias shot noise dip. An increase in magnetic gap will suppress the tunnel conductance and shot noise when the conventional Andreev retro-reflection dominates, but will enhance them when the specular Andreev reflection is dominant. Both specular Andreev reflection and conventional Andreev retro-reflection will be enhanced as the quasi-particle lifetime increases. When Fermi energy equals the magnetic gap, shot noise and tunneling conductance vanish across all energy ranges. These findings not only contribute to a better understanding of specular Andreev reflection in the FM/f–wave SC junction based on TIs but also provide insights for experimentally determining the f-wave pairing symmetry.

Reaction Mechanism and Structural Evolution of Tunnel‐Structured KCu7S4 Nanowires in Li+/Na+‐Ion Batteries

AbstractSelecting suitable electrode materials for sodium‐ion batteries (SIBs) often relies on the experience gained from lithium‐ion batteries (LIBs), particularly in terms of thermodynamics. However, this approach may fall into a stagnant situation where the development of SIBs consistently lags behind that of LIBs due to the larger ionic radius of Na+. Accordingly, it is crucial to establish a dedicated selection rule specifically tailored for SIB electrodes to overcome this challenge. Herein, a screening method is proposed for SIB materials, where an ideal candidate shall form a stable intermediate transition phase with Na+. This phase acts as an important bridge that can regulate the insertion/extraction of charge carriers. Atomically resolved transmission electron microscopy demonstrates that KCu7S4 can react with Na+ to form a stable intermediate phase (Na3Cu4S4). Na3Cu4S4 can undergo reversible conversion reactions, contribute capacity, stabilize the tunnel structure and enhance the migration/diffusion of Na+. In contrast, Li+ can't form a stable intermediate phase in KCu7S4 during lithiation/delithiation, thus losing the ability to effectively regulate Li+ insertion/extraction. These findings provide valuable insights for the development of suitable electrode materials for SIBs, emphasizing the importance of stable intermediate phases in regulating charge carrier insertion/extraction and improving overall battery performance.

Numerical study on the smoke temperature distribution beneath the ceiling of a single-ended sealing tunnel under the condition of double fire sources

As a special tunnel structure, the single-ended sealing tunnel has only one evacuation port, which increases greatly the risk of fire. Numerical modeling of a double source fire in a single-ended sealed tunnel was developed based on FDS 6.7. The effects of double-source spacing and end walls on ceiling smoke temperature were analyzed and discussed. The results show that when the double fire sources are considered as a whole, there are varying degrees of smoke backflow throughout the tunnel, with the upstream smoke backflow phenomenon being more pronounced under the influence of the end wall. In this study, the dimensionless separation distance φ is introduced and divided into two regions to quantify the effect of the spacing of the double fires. When 0 ≤ φ < 0.625, the maximum smoke temperature beneath the ceiling falls exponentially with increasing separation distance. On the other hand, when 0.625 < φ ≤ 1, the maximum smoke temperature under the ceiling rises exponentially. Furthermore, we suggest empirical formulas for forecasting the longitudinal distribution of downstream temperatures as well as the maximum smoke temperature of the ceiling. The predictive equations’ dependability was further confirmed by contrasting the predicted equations with simulated and historical experimental data. The study results serve as a reference for fire prevention and rescue in similar special tunnel structures, such as single-end sealing.

High-precision imaging of small voids in tunnel lining based on reverse time migration

Abstract Diseases such as voids behind the initial support of the tunnel will lead to problems such as lining rupture and concrete damage in the tunnel structure, which seriously affects the driving safety in the tunnel. In tunnel construction, ground penetrating radar is frequently employed as a method for detecting hidden defects. However, when the cavity size is small, there will be a large error when the original radar data is directly interpreted, which cannot meet the needs of practical engineering. To enhance the precision in tunnel detection, the Finite-Difference Time-Domain method is used to simulate various small cavities of different shapes located behind the primary support lining of the tunnel, and the study involves examining the electromagnetic response characteristics of different kinds of holes. The migration techniques of KIRCHHOFF, F-K, and reverse time are employed to reconstruct the hole target. Furthermore, digital morphology is employed to enhance the clarity of the image. Finally, the edge detection technology is used to further extract the hole features. After that, small cavities of different shapes are buried in the established outdoor concrete model box and radar detection is carried out. The detection position of the reconstructed radar image and the actual position of the cavity in the model box are verified. The results show that compared with KIRCHHOFF migration and F-K migration, the image processed by reverse time migration is clearer and more intuitive, and can restore the contour of small holes well. The research findings can serve as a reference for the interpretation of radar data of the cavity behind the initial support of the tunnel.

Construction of advanced Nb9VO25 electrode material by introducing graphene quantum dot for high energy supercapacitors with exceptionally high diffusive capacitance

Unreasonable tunnel structure and low intrinsic conductivity limit practical applications of niobium oxide in high-performance supercapacitors. The study reports the construction of Nb9VO25 electrode material via coordination of Nb(V) and V(V) with histidine and serine-functionalized and boron-doped graphene quantum dot (HSBGQD) and subsequent annealing. The introduction of HSBGQD and rambutan peel leads to formation of small Nb9VO25 nanocrystal and low valent Nb and V species. The combination of small size and more reasonable tunnel structure accelerates the ion diffusion. The Nb(IV) and V(IV) double doping optimizes the tunnel structure, narrows the bandgap and creates new pathways for high-speed electron transfer. The integration of defect engineering with graphene surface modification enhance the intrinsic conductivity. The Nb9VO25 electrode shows exceptionally high specific capacitance of 2925.3 F/g, which is more than 142 times that of Nb2O5. The symmetrical supercapacitor with Nb9VO25 electrodes and PVA/Li2SO4 gel electrolyte offers high specific capacitance (263 F/g at 1 A/g), high-rage capacity (138 F/g at 50 A/g), cycling stability (capacitance retention of 99.4 % after 10000-cycle), energy density (146 W h Kg−1 at 996 W Kg−1 and 77 W h Kg−1 at 50181 W kg−1) and broad application prospect in wearable electronic devices.

Disturbance characteristics test about double-line shield tunnel excavation in grouting-reinforced water-rich sand stratum

To study the disturbance characteristics of double-line shield tunnel excavation on sand bodies in grouting-reinforced water-rich sand stratum, a similar model test was carried out. Firstly, the physical parameters and strength indexes of the overlying soil strata of the tunnel in the water-rich sand stratum were determined by laboratory tests. The similar soil and tunnel support structures of each stratum were prepared. Then, considering the different seepage modes of upper and lower soil strata under the influence range of tunnel excavation, the model test of double-line shield tunnel excavation in a grouting-reinforced water-rich sand stratum is conducted. The variation rules of sand deformation, surface settlement, and sand body stress during the excavation of a double-line shield tunnel are analyzed utilizing monitoring and analyzing systems such as a flowmeter, micro earth pressure sensors, and dial indicators. It is found that during the excavation of the double-line tunnel, the self-stabilization ability of the grouting reinforced sand bodies is strong under the action of stable seepage. Under the influence of grouting reinforcement, the seepage path around the tunnel structure will change, the fluid-solid coupling effect will decrease, and the sand stratum will be uplifted to varying degrees. The sand body will change its mechanical properties due to the influence of seepage. The fluid-solid interaction effect will be enhanced. The fluid-solid coupling effect of soil particles and water will be further enhanced when the excavation of the subsequent tunnel is carried out. The effect of unsaturated seepage in the overlying soil stratum leads to greater stress at the arch waist of the arch tunnel. In the actual construction process, the grouting amount and grouting time should be strictly controlled. The tunnel basement is supported by anchor spray support to prevent the tunnel structure and surface uplift.

An improved analytical solution for solving the shield tunnel uplift problem

The problem of shield tunnel uplift is a common issue in tunnel construction. Due to the decrease in shear stiffness at the joints between the rings, uplift is typically observed as bending and dislocation deformation at these joints. Existing modeling methods typically rely on the Euler-Bernoulli beam theory, only considering the bending effect while disregarding shear deformation. Furthermore, the constraints on the shield tail are often neglected in existing models. In this study, an improved theoretical model of tunnel floating is proposed. The constraint effect of the shield machine shell on the tunnel structure is considered using the structural forms of two finite long beams and one semi-infinite long beam. Furthermore, the Timoshenko beam theory is adopted, providing a more accurate description of tunnel deformation, including both the bending effect and shear deformation, than existing models. Meanwhile, the buoyancy force and stratum resistance are calculated in a nonlinear manner. A reliable method for calculating the shear stiffness correction factor is proposed to better determination of the calculation parameters. The proposed theoretical model is validated through five cases using site-monitored data. Its applicability and effectiveness are demonstrated. Furthermore, the influences of soil type, buried depth, and buoyancy force on the three key indicators of tunnel floating (i.e. the maximum uplift magnitude, the ring position with the fastest uplift race, and the ring position with the maximum uplift magnitude) are analyzed. The results indicate that the proposed model can provide a better understanding of the floating characteristics of the tunnel structure during construction.

Воздействие криогенных сред и струйного горения на эпоксидные интумесцентные композиции, предназначенные для защиты оборудования и строительных конструкций нефтегазового комплекса

The article discusses the studies of epoxy intumescent fire-protective coating of steel structures impacted by cryogenic media and jet fire, in accordance with the requirements of the methodology developed at the Orenburg branch of the Federal State Autonomous Educational Institution of Higher Education VNIIPO EMERCOM of Russia, and harmonized with the international standards ISO 22899-1:2021, ISO 20088-1:2016, and ISO 20088-3. The tests have been conducted with the epoxy fire- and cryogenic-protective intumescent composition «Plamkor-5» (produced by JSC Scientific and Production Holding «VMP», Yekaterinburg, Russia). According to the results of the test for resistance of a square-shaped sample with internal dimensions 1500×1500×500 mm and a central shelf made of 10 mm thick carbon steel coated with the fire-retardant composition «Plamkor-5» to cryogenic fluid spill, it has been established that the sample does not reach the critical temperature of minus 49 °C with an actual 22.37 mm dry layer thickness. The average sample temperature at the 60th minute of the test was minus 32.09 °C. The results of the test of a similar sample in order to determine the resistance of the fire-protective composition «Plamkor-5» to a jet fire with an actual 10,89 mm thickness of the protective dry layer have shown that the sample does not reach the critical temperature of 500 °С during 60-minute fire exposure, whereas the average temperature of the sample was only 37 % (184.84 ºС) of the temperature limit value. According to the results of the test for resistance of a steel column shape sample of I-section 25K2 coated with the fire-retardant composition «Plamkor-5» to spill under the pressure of the cryogenic liquid, it has been established that the sample does not reach the critical temperature of minus –49 °С with an actual 23.78 mm dry layer thickness, whereas the average temperature of the sample at the 60th minute of test was minus 48.38 °С. The obtained results are comparable with the effect of the best import analogs; therefore, «Plamkor-5»-based fire-protective coatings can be used for the design and development of fire protection of building structures, at the facilities of the oil and gas industry, in tunnel structures, and civil engineering.

Introducing Ce ions and oxygen vacancies into VO2 nanostructures with high specific surface area for efficient aqueous Zn-ion storage

Positive electrodes play a decisive role in exploring the Zn2+ storage mechanism and improving the electrochemical performance of aqueous Zn-ion batteries (AZIBs). Feasible design and preparation of cathode materials have been crucial for AZIBs in recent years. Herein, taking the advantage of the tunnel structure of VO2, which can withstand volume change during charging/discharging, VO2 doped with Ce ions is synthesized by a simple one-step hydrothermal method and oxygen vacancies are synchronously generated during synthesis. It delivers a capacity of 158.5 mAh g−1 at the current density of 5 A g−1 after 1000 cycles and exhibits an excellent energy density of 312.8 Wh kg−1 at the power density of 142 W kg−1. The structural modification and prospect of enhancing its conductivity by doping with rare-earth metals and introducing oxygen vacancies may aid in improving the stability of AZIBs in the future.

Automated method for structural modal identification based on multivariate variational mode decomposition and its applications in damage characteristics of subway tunnels

This paper introduces a fully automated modal identification algorithm based on the Multivariate Variational Mode Decomposition (MVMD) of free vibration responses to determine structural modal parameters. Addressing the challenge of setting MVMD parameters, we introduce a fusion parameter combining power spectral cross-entropy with reconstruction error as an adaptive fitness function in the optimization algorithm, enabling optimal parameter selection. Then, modal frequencies, damping ratios, and shapes of structures can be extracted from autonomously decomposed Intrinsic Mode Functions by employing the principle of modal superposition and least squares fitting without manual parameter adjustments. Validated by a four-degree-of-freedom numerical model, the method demonstrated accurate, automatic modal parameter identification. The method was further applied to a subway tunnel structure model experiment. Comprehensive modal identification was conducted on tunnel structures under varying degrees of damage. The results validate the proposed method’s effectiveness and reveal the damaged segment structure’s multimodal parameter variation patterns and surrounding soil.

Analysis of loess water migration regularity and failure response of tunnel structure under rainfall environment

Analysis of loess water migration regularity and failure response of tunnel structure under rainfall environment

Numerical Simulation Study Considering Discontinuous Longitudinal Joints in Soft Soil under Symmetric Loading

In shield tunneling, the joint is one of the most vulnerable parts of the segmental lining. Opening of the joint reduces the overall stiffness of the ring, leading to structural damage and issues such as water leakage. Currently, the Winkler method is commonly used to calculate structural deformation, simplifying the interaction between segments and soil as radial and tangential Winkler springs. However, when introducing connection springs or reduction factors to simulate the joint stiffness of segments, the challenge lies in determining the reduction coefficient and the stiffness of the springs. Currently, the hyperstatic reflection method cannot simulate the discontinuity effect at the connection of the tunnel segments, while the state space method overlooks the nonlinear interaction between the tunnel and the soil. Therefore, this paper proposes a numerical simulation method considering the interaction between the tunnel and the soil, which is subjected to compression rather than tension, and the discontinuity of the joints between the segments. The model structure and external load are symmetrical, resulting in symmetrical calculation results. This method is based on the soft soil layers and shield tunnel structures of the Shanghai Metro, and the applicability of the model is verified through deformation calculations using three-dimensional laser scanning point clouds of sections from the Shanghai Metro Line 5. When the subgrade reaction coefficient is 5000 kN/m3, the model can effectively simulate the deformation of operational tunnels. By adjusting the bending stiffness of individual connection springs, we investigate the influence of bending stiffness reduction on the bending moment, radial displacement, and rotational displacement of the ring. The results indicate that a decrease in joint bending stiffness significantly affects the mechanical response of the ring, and the extent and degree of this influence are correlated with the joint position and the magnitude of joint bending stiffness.

Rational optimization of substituted α‐MnO2 cathode for aqueous zinc‐ion battery

AbstractDensity functional theory (DFT) is utilized to explore the effects of increasing concentrations of vanadium (V) and chromium (Cr) substitution on the discharge of α‐MnO2 cathode in hydrated zinc‐ion batteries (ZIBs). During H+‐intercalation and Zn2+‐intercalation, Cr‐substitution proves to be more effective than V‐substitution in promoting discharge behaviors. Transitioning from Mn0.875Cr0.125O2, Mn0.75Cr0.25O2 to Mn0.625Cr0.375O2 is found to consistently enhance the discharge voltage, along with improved tunnel structure retention and volume expansion suppression. In comparison, the promoting effect of increasing V‐substitution is relatively small at initial discharge stages and leads to degradation at later stages, primarily due to an increased concentration of unstable Mn2+ ion. The superior effect of Cr‐substitution is attributed to the unique atomic and electronic structures of substituted Cr4+ and reduced Cr3+ ions during discharge. These ions serve as active electron acceptors to limit the formation of Mn3+ and Mn2+ ions, and as anchors to stabilize the α‐MnO2 framework and intercalated H+/Zn2+ ions, respectively. Our study highlights fine‐tuning through substitution to enhance the performance of α‐MnO2‐based cathode materials in ZIBs.

Mechanical Response and deformation mechanism of the utility tunnel crossing earth fissure

The structural safety of the utility tunnel is adversely affected when it passes through an area with earth fissures. Using the comprehensive tunnel project at the f7 earth fissure site in Xi'an as the engineering prototype, finite element simulation was employed to investigate the mechanical responses and deformation laws of the utility tunnel under different relative positions of earth fissures and deformation joints. Simultaneously, the deformation mechanism of a utility tunnel crossing an earth fissure was explored by using theoretical analysis. The results show that the influence of the earth fissure on the surface deformation of the hanging wall is greater than that of the footwall, and the main deformation is near the earth fissure. In addition, because the rigidity of the utility tunnel greatly exceeds that of the soil, the surface deformation at the earth fissure does not show a sudden change in form as dislocation generated by the hanging wall and footwall. Earth fissure movement mainly affects the stress change in the utility tunnel in the crossing ground fissure section. Moreover, the void area will be generated by the dislocation of the earth fissure near the earth fissure position at the bottom of the utility tunnel, which is not conducive to the stress of the utility tunnel. The research results contribute to optimizing the design of utility tunnel projects and enhancing the structural safety of tunnels. Additionally, they provide important reference points for the maintenance and management of comprehensive utility tunnels, enabling timely identification and resolution of the impacts of earth fissures on tunnel structures, thus ensuring the long-term stable operation of the tunnels.

Health Risk Prediction of Operational Subsea Tunnel Structure Based on Bayesian Network

Recently, subsea tunnel construction has developed rapidly in China. The traffic volume of subsea metro tunnels is large. Once a safety accident occurs, economic losses and social impacts will be extremely serious. To eliminate accidents in operational subsea metro tunnel structures, a health risk prediction method is proposed based on a discrete Bayesian network. Detecting and monitoring data of the tunnel structures in operation were used to evaluate the health risk by employing the proposed method. This method establishes a Bayesian network model for the health risk prediction of the shield tunnel structure through the dependency relationship between the health risk of the operational tunnel structure and 13 risk factors in five aspects: the mechanical condition, material performance, integrity state, environmental state, and deformation state. By utilizing actual detection and monitoring data of various risk factors for the health risk of the operational subsea metro shield tunnel structure, this method reflects the actual state of the tunnel structure and improves the accuracy of health risk predictions. The validity of the proposed method is verified through expert knowledge and the subsea shield tunnel structure of the Dalian Subway Line 5. The results demonstrate that the health risk prediction outcomes effectively reflect the actual service state of the shield tunnel structure, thus providing decision support for the control of health risks in the subsea metro shield tunnel.