Search Results (34)

Submerged tunnels are an innovative infrastructure solution for connecting roads and railways, especially in areas where conventional bridge or overland tunnel construction is limited by deep waterways, narrow straits, or dense urban development. In such regions, submerged tunnels offer an efficient and less intrusive alternative that overcomes geographical constraints. However, unlike conventional ground-level or subsea tunnels, submerged tunnels have unique structural and environmental characteristics, which necessitate the development of a dedicated evaluation system for responding to fire and other disasters. In this study, a quantitative fire risk assessment program (SFT_QRA) was developed by reflecting the specific characteristics of submerged tunnels. The program was applied to both road and railway tunnels to obtain evaluation results. First, to more realistically reflect the fire risk within submerged tunnels, the latest statistical data were used to update fire occurrence probabilities and the proportion of vulnerable users. In addition, the optimal smoke control mode for structural stop zones in ultra-long tunnels was analyzed to derive strategies for establishing a safe evacuation environment. Second, an Excel VBA-based assessment program was developed to improve user convenience and was structured to enable fire analysis and evacuation simulations. Third, in order to verify the accuracy and reliability of the developed program, a comparative analysis was conducted against commercial quantitative risk assessment programs. As a result, the total risk error rate was 0.4% for road tunnels and within 5.0% for railway tunnels, showing similar levels of results. This study advances quantitative risk assessment methods by incorporating the unique features of submerged tunnels and implementing them in a validated program. Through this approach, it presents a practical solution that can contribute to the advancement of tunnel fire safety technologies and the overall enhancement of tunnel safety. Full article

Subsea tunnels cross complex geological structures, such as weathered troughs with fractured rock masses and high permeability, and are prone to water and mud inrush. To minimize the risk of subsea tunnelling, a novel method consisting of a multi-index evaluation system and a computational model using the interval number TOPSIS method was established. The multi-index evaluation system was formed by eight evaluation indices that can potentially affect water and mud inrush: sea depth, subsea tunnel burial depth, scale of weathering trough, interface angle, strength of surrounding rock, permeability of weathering trough, cyclical footage, and grouting reinforced region. The risk levels of water and mud inrush were divided into four grades. Considering the uncertainty of the evaluation indices, an evaluation vector of interval numbers was adopted. The triangular fuzzy number membership function was used to determine the membership degree, and the 1–9 scales method was used to construct the judgment matrices, which can obtain the weight of evaluation indices. Furthermore, the weight values of the evaluation indices combined with the membership degree were used to obtain the result vector, which can be analyzed using the interval number TOPSIS method. This novel assessment method was applied to the FWK15+350 of the Haicang tunnel successfully. The risk level fell into IV, which represents a high-risk section. The results showed a high degree of congruence with the prevailing circumstances, thereby validating the credibility of the proposed methodology. Full article

Deep-buried subsea tunnels are often under high water pressure conditions, and the influence of the seepage field on the tunnel cannot be ignored. Existing studies generally assume that the surrounding rock exhibits permeability isotropy; this study developed a model of deep-buried subsea tunnel that considers the permeability anisotropy of surrounding rock and investigated the effects of permeability differences between the surrounding rock and lining structure on tunnel seepage flow and plastic zone extent. By employing coordinate transformation and conformal mapping methods, the hydraulic head and the seepage discharge for each region are determined for each section of the tunnel. Based on the analytical solution of the seepage field, the seepage force is treated as a body force, and using the Mohr–Coulomb criterion, an elastoplastic analytical solution for the lining and surrounding rock under anisotropic seepage is derived. Using the Shenzhen MaWan Sea-Crossing Passage as a case study, numerical simulations are conducted using Abaqus2021, and the results are compared with the analytical solution to verify the accuracy of the study. The research shows that the permeability anisotropy of surrounding rock increases the seepage discharge, and this effect becomes more significant with increasing burial depth. If the anisotropy is 10 times greater than its previous value, the tunnel seepage volume will increase by 35.6%. When the surrounding rock permeability is sufficiently large, the impact of permeability anisotropy on the seepage discharge is relatively weak, with the seepage discharge primarily dominated by the permeability of the lining. In the tunnel stress field, due to the significant difference in stiffness between the lining and the surrounding rock, the hoop stress in the lining is much larger than that in the surrounding rock, and there is a stress discontinuity at their interface. When the permeability of the elastic zone of the surrounding rock is 100 times greater than that of the plastic zone, the plastic radius of the tunnel will increase by 2 to 3 times compared to the previous value. Reducing the permeability of the plastic zone in the surrounding rock effectively limits the seepage body force acting on the lining, thereby enhancing the stability of the lining structure and reducing the risk of damage to the tunnel. Full article

The large-diameter slurry tunnel boring machine (TBM) is widely used in the construction of tunnels across rivers and seas. However, cutter wear has become a critical issue that severely limits the tunnelling efficiency. Taking the Qingdao Jiaozhou Bay Second Subsea Tunnel Project as the background, the wear patterns of disc cutters on the atmospheric cutterhead of a large-diameter slurry TBM under complex geological conditions were analyzed. The flat wear of disc cutters induced by factors such as rock chip accumulation in front of the cutterhead, the jump trajectory when changing disc cutters, alloy-insert disc cutter mismatch, cutter barrel clogging, and severe wear of scrapers is discussed. Furthermore, the impacts of measures such as slurry circulation to remove rock chips during TBM stoppage, clay dispersant injection into the slurry chamber, cutter barrel flushing, and the wear resistance optimization of cutters and cutter barrels on reducing cutter wear were investigated. Based on numerical simulations and field data, a methodology for determining the optimal timing for cutter replacement is proposed. The results indicate the following: The circulation system effectively reduces accumulation, minimizing secondary wear of the disc cutters and lowering the risk of clogging in the cutter barrel. Adopting measures such as shield shutdown, a circulation system to carry away the slag, cutter barrel flushing, and soaking in 2% dispersant for 8 h can effectively reduce the accumulation of rock chips and mud cakes on the cutterhead, which in turn reduces the flat wear of the disc cutter. Measures such as making the cutter body and cutter ring rotate together and adding wear-resistant plates to the cutter barrel greatly improve the life of the cutter. The sharp increase in composite parameters can serve as an effective marker for assessing cutter conditions. The findings of this study can provide valuable insights into reducing cutter wear in similar projects. Full article

Understanding the long-term durability and degradation mechanisms of steel fiber-reinforced concrete (SFRC) linings in subsea tunnels is critical for ensuring structural safety, cost effectiveness, and sustainability. This study investigated the degradation characteristics of SFRC with varying fiber contents (0%, 0.35%, 0.55%, and 0.75%) and different acceleration durations, using the applied electric field acceleration method and X-ray CT tests. The experimental results revealed the characteristics of the surface crack distribution and evolution patterns in the SFRC specimens. Furthermore, the similarity between the non-uniform corrosion patterns observed in regard to accelerated corrosion under the applied electric fields and those occurring due to natural degradation was verified. The pore structure characteristics and internal crack development of the SFRC specimens were compared. The study found that the degradation process of the specimens was closely related to the fiber content. The incorporation of steel fibers altered the crack initiation and propagation modes, leading to a more scattered crack distribution. The accelerated corrosion method, employing an applied electric field, successfully simulated the non-uniform corrosion process of reinforcement in SFRC linings in subsea tunnels under natural conditions. Under the influence of a unidirectional chloride ingress source, the pronounced accumulation of corrosion products was observed only on the side of the reinforcement exposed to chloride penetration. This method effectively visualized the chloride penetration path and its impact on reinforcement corrosion, providing valuable insights for the anti-corrosion design of SFRC linings in subsea tunnels. Full article

Subway tunnels excavated in soil–rock composite strata face great challenges due to the prevalence of inner defects. The instability of tunnels in these strata poses significant risks to construction safety. In this paper, indoor experiments are adopted to study the instability process of a subway tunnel in soil–rock composite strata influenced by inner cavities. A total of six groups of tests are designed based on the location of the cavity and the distance of the cavity from the tunnel. High-resolution monitoring techniques are employed to capture the real-time deformation and failure process of strata. The results show that a cavity in the strata significantly affects the stability of the strata after the tunnel excavation. The existence of a cavity increases ground deformation, and a cavity at different locations affects ground deformation. The strata around the cavity are the first to experience failure by the upper loads applied after the tunnel is excavated. The location of the cavity changes the stress distribution state of the strata and thus alters the emergence of cracks, which finally disturbs the collapse process and pattern of the composite strata. The probability and collapse range increase when the tunnel excavation impact zone is connected with the cavity weakening zone. The findings can provide technical support for the collapse prevention and safety control of subway tunnels in composite strata with internal defects. Full article

Due to complex geological conditions and external environmental factors, the structural safety of tunnels faces many challenges. In order to achieve real-time monitoring and early warning for tunnel safety, this paper proposes a semi-supervised clustering algorithm, named SSCME. First, in the traditional concept drift detection stage, this algorithm improves traditional methods by utilizing data distribution to calculate the concept deviation and accurately identify four different types of concept drift. Second, in the incremental update stage, the EM algorithm is further optimized to remove the outlier data used for incrementally updating the classifier, thus resolving the sensitivity issue of DBSCAN in parameter selection. Finally, a large number of sensors are installed in multiple tunnels to collect data and construct datasets. The experimental results on multiple datasets demonstrate that, compared with existing baseline methods, this algorithm has higher effectiveness and reliability. Full article

The composite performance of steel fiber-reinforced concrete (SFRC) is excellent, and its application potential in subsea tunnel engineering has gradually emerged. This paper discusses three types of laboratory testing methods for studying the corrosion of SFRC induced by chlorides: the ion diffusion method, electric field migration method, and pre-corrosion method. The similar relationship between short-term accelerated deterioration tests and the natural corrosion process, as well as the experimental setup for simulating the coupling effect of multiple factors, requires further exploration. Furthermore, the mechanisms of steel fibers influencing the chloride corrosion resistance of SFRC are explored from four aspects: type, coating, shape, and dosage. Finally, by examining practical case studies of SFRC in subsea tunnel applications, the challenges posed by the multi-directionality of chloride ion corrosion, the diversity of corrosion sources, and the uneven distribution of steel fibers are highlighted. Future research should focus on enhancing the application of SFRC in subsea tunnel linings. This study provides a reference and basis for promoting the application of SFRC in subsea tunnel engineering and indicates future development directions. Full article

Ion erosion has a significant impact on the long-term service performance of lining structures in the subsea tunnel and seriously affects its sustainability. Indoor tests are usually used to study the erosion behavior of lining concrete specimens to reveal the degradation pattern of ion erosion. However, the long-term service performance of lining structures under ion erosion is rarely considered in the industry. In this study, the long-term deterioration characteristics of concrete specimens and subsea tunnel linings are analyzed by using numerical investigations. The long-term diffusion patterns of erosion ions in concrete specimens are evaluated. The effects of ion erosion and water pressure on the stress, deformation, and damage characteristics of the lining structure are examined. The numerical results show that solution concentrations and concrete grades have a significant influence on the ion diffusion in concrete specimens. As the erosion time increases, the rate of ion diffusion gradually decreases due to the decrease in the concentration difference between the inside and outside of the concrete. The service time T has a significant effect on the depth and rate of ion erosion. When T is 10, 50, and 100 years, the depth of ion erosion reaches 25, 63, and 84 mm, respectively, showing a nonlinear increase. As the depth of ion erosion increases, the characteristic parameters reflecting the long-term performance of the lining structure will increase. The maximum tensile stress is 0.98 MPa, and the maximum displacement is 1.59 cm, both of which occur at the arch crown. Disregarding the effects of ion erosion and water pressure, the vertical displacements of the lining structure within the first two years under low loads account for more than 97% of the 100-year displacements. Both ion erosion and water pressure exacerbate the damage deterioration of the lining, in which ion erosion significantly increases the maximum tensile stress of the lining, with a maximum enhancement of 326.09%, and water pressure significantly enlarges the maximum compressive stress of the lining, with a maximum enhancement of 53.23%. However, with increasing depths of ion erosion, the high water pressure will reduce the maximum tensile stress. This study can lay the foundation for further research on the long-term stability of the lining under complex erosion environments. Full article

Based on the structural and geological characteristics of the F1 weathering trough of a submarine tunnel and its spatial relationship with the cavern, a simplified calculation model of the weathering trough water inrush was established, and the formation, development process and influencing factors of the water inrush channel in the water-resistant rock layer were carried out by a numerical simulation of particle flow. It shows that the integrity and stability of the critical water-resistant rock mass is the key to preventing water inrush, and the identification and positioning of the water inrush channel is the basis for the grouting reinforcement design of the weathering groove of the submarine tunnel. Based on above research results, the F1 weathering trough was blocked and reinforced by the composite grouting method, and the engineering reinforcement effect was good. Full article

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. Full article

The rock strength in an active fault zone is low and the surrounding rock is fractured and has poor stability, making any subsea tunnel crossing the active fault zone extremely susceptible to disasters such as tunnel collapse, sudden water ingress, and mud inrush. This poses a potential threat to the construction project, making the dynamic stability analysis of a subsea tunnel crossing an active fault zone of great significance. This study takes the second subsea tunnel crossing the Cangkou Fault in Jiaozhou Bay as the engineering background and conducts numerical simulations by employing different lining stiffnesses for tunnel excavation, as well as applying dynamic loads. The dynamic stability of the subsea tunnel crossing the active fault zone is evaluated by comparing and analyzing the lining’s displacement, peak acceleration, and stress characteristics. This study explores the disaster-causing mechanisms of active fractures, determining that the hazard of orthogonal misalignment in an active fault zone is the least severe, while the hazard of opposite misalignment is the most severe. This research provides a basis for disaster prevention and mitigation in active fracture zones. Full article

Submerged floating tunnels (SFTs), also known as the Archimedes Bridge, are new transportation structures designed for crossing deep waters. Compared with cross-sea bridges and subsea tunnels, SFTs offer superior environmental adaptability, reduced construction costs, and an enhanced spanning capacity, highlighting their significant development potential and research value. This paper introduces a new type of SFT scale model for hydrodynamic experiments, adhering to the criteria for geometric similarity, motion similarity, and dynamic similarity principles, including the Froude and Cauchy similarity principles. This model enables the accurate simulation of the elastic deformation of the tunnel body and complex hydrodynamic phenomena, such as fluid–structure interactions and vortex–induced vibrations. Moreover, this paper details the design methodology, fabrication process, and method for similarity evaluation, covering the mass, deflection under load, natural frequency in air, and the natural frequency of the various underwater motion freedoms of the model. The results of our experiments and numerical simulations demonstrate a close alignment, proving the reliability of the new SFT scale model. The frequency distribution observed in the white noise wave tests indicates that the SFT equipped with inclined mooring cables experiences a coupled interaction between horizontal motion, vertical motion, and rotation. Furthermore, the design methodology of this model can be applied to other types of SFTs, potentially advancing technical progress in scale modeling of SFTs and enhancing the depth of SFT research through hydrodynamic experiments. Full article

With the advent of the era of big data and information technology, deep learning (DL) has become a hot trend in the research field of artificial intelligence (AI). The use of deep learning methods for parameter inversion, disease identification, detection, surrounding rock classification, disaster prediction, and other tunnel engineering problems has also become a new trend in recent years, both domestically and internationally. This paper briefly introduces the development process of deep learning. By reviewing a number of published papers on the application of deep learning in tunnel engineering over the past 20 years, this paper discusses the intelligent application of deep learning algorithms in tunnel engineering, including collapse risk assessment, water inrush prediction, crack identification, structural stability evaluation, and seepage erosion in mountain tunnels, urban subway tunnels, and subsea tunnels. Finally, it explores the future challenges and development prospects of deep learning in tunnel engineering. Full article

The issue of water seepage poses a significant challenge in tunnel infrastructure. Wet areas are commonly used to evaluate the degree of water seepage in tunnel projects. To investigate the feasibility for numerical simulation to predict a wet area, we selected concrete test blocks with two types of defects—holes and cracks—as the research specimens. Numerical models for various seepage conditions were constructed using TOUGH2, and the results were validated through laboratory experiments. Additionally, the Shenjiamen Subsea Tunnel was simplified into a numerical model, employing TOUGH2 to forecast its future wet area performance within the scope of national standards. The outcomes of our research revealed that point seepage and line seepage exhibited circular and elliptical morphologies, respectively. Moreover, external water pressure and defect size exerted a significant influence on the expansion of the wet area. Notably, the impact of crack width surpassed that of hole diameter. Encouragingly, the numerical models generated using TOUGH2 for unsaturated concrete demonstrated excellent agreement with laboratory test results concerning the geometry, size, and pattern of the wet area. These findings signified the potential of TOUGH2 numerical simulation as a valuable tool in predicting the lifespan of tunnels. Full article