Search Results (296)

Dense and complex underground structures impose stringent requirements on shield tunneling. In the close-proximity construction of super-large-diameter shield tunnels, challenges may arise, including adverse impacts on the normal operation of existing structures, as well as difficulties in ensuring the bearing capacity and deformation control of these structures during excavation. This study, based on the stratigraphic conditions of the Chengdu area, employs FLAC3D 7.0 version software to simulate the section where the Shuanghua Road Tunnel underpasses both Metro Line 10 and the Chengdu-Guiyang High-Speed Railway. The main conclusions are as follows: (1) Tunnel underpassing induces uneven settlement in the metro tunnel, with a maximum settlement reaching 47.7 mm. The settlement trough exhibits a twin-peak morphology during dual-line construction. When a single super-large-diameter tunnel line crosses the existing structural cluster, the maximum settlement is located directly above the crossing point. During dual-line crossing, the maximum settlement shifts towards the midpoint between the two new tunnel lines. (2) As the left line of the new tunnel approaches the existing structure, the cross-sectional deformation of the existing structure is “pulled” towards the direction of the excavated new tunnel. After the new left line moves away, the cross-sectional deformation gradually recovers to a bilaterally symmetrical state. (3) The tunnel cross-section undergoes dynamic “compression-tension” convergence changes during the construction process, with a maximum longitudinal tensile convergence of −1.28 mm. (4) During the underpassing of the existing structural cluster by the super-large-diameter tunnel, the maximum torsion angle is approximately −0.016°, occurring at the moment when the shield machine head first passes directly beneath, located directly above the new tunnel. The torsion angle of the existing structure is greatest during the first underpassing event, and the maximum torsion angle during the second underpassing is lower than that during the first. This study reveals the composite deformation mode of “settlement-convergence-torsion” during the underpassing of existing structural clusters by super-large-diameter shield tunnels, providing a theoretical basis for risk control in similar adjacent engineering projects. Full article

In high-speed railways, the reliability of jointless track circuits largely hinges on the operational integrity of compensation capacitors. These capacitors are periodically installed along the track to mitigate rail inductive impedance and stabilize signal transmission. The induced voltage response, referred to as the compensation-capacitor signal, serves as a critical diagnostic indicator of circuit health. Yet it is often distorted by electromagnetic interference and structural resonance, posing significant challenges for robust feature extraction. To address this challenge, we propose a Disturbance-Robust Feature Distillation (DRFD) framework that performs multi-perspective modeling and validation of robust features. The framework formulates a unified multi-objective optimization model that jointly considers statistical significance, environmental stability, and structural separability. These objectives are harmonized through an adaptive Bayesian weighting mechanism, enabling automatic identification of disturbance-resistant and discriminative features under complex operating conditions. Experimental evaluations on real-world datasets collected at a 100 kHz sampling rate from roadbed, tunnel, and bridge environments demonstrate that the DRFD framework achieves 96.2% accuracy and 95.4% F1-score, outperforming the best-performing baseline by 4.2–7.8% in accuracy and 6.5% in F1-score. Moreover, the framework achieves the lowest cross-condition relative variance (RV < 0.015), confirming its high robustness against electromagnetic and structural disturbances. The extracted core features—Root Mean Square (RMS), Peak Factor (PF), and Center Frequency (CF)—faithfully capture the intrinsic electromagnetic behaviors of compensation capacitors, thus linking statistical robustness with physical interpretability for enhanced reliability assessment of railway signal systems. Full article

With the rapid expansion of high-speed railway (HSR) networks, the vibration impact on adjacent energy infrastructure has become a critical safety concern. However, existing research lacks a comprehensive evaluation of buried sour gas pipelines specifically in tunnel-undercrossing scenarios. This research investigates the dynamic response characteristics of a sour natural gas pipeline under train-induced vibration loads using a case study in Chongqing. A three-dimensional dynamic coupling model of the track lining soil pipeline system was established based on FLAC-3D. The study innovatively quantifies the vibration superposition effect during bidirectional train encounters and assesses safety using fatigue life and velocity thresholds. Results indicate that pipeline vibration is predominantly vertical. As train speed increases from 250 km/h to 350 km/h, the response exhibits a non-linear rapid growth within the 300–350 km/h range. Under bidirectional encounters, the peak displacement reaches 2.00 times that of unilateral passage, representing the most critical load condition. The maximum peak vibration velocity is 0.1 mm/s, far below the 2 mm/s safety threshold, ensuring structural integrity under current operational standards. Full article

In submerged tunnel construction, the installation accuracy of pre-embedded components directly impacts subsequent engineering quality and operational safety. However, current on-site construction still primarily relies on manual measurement and two-dimensional drawings for guidance, resulting in significant positioning errors, delayed information transmission, and inefficient installation inspections. To enhance the digitalization and intelligence of submerged tunnel construction, this paper proposes a BIM- and AR-based human–machine collaborative management method for pre-embedded components in submerged tunnel segments. This method establishes a site-wide panoramic model as its foundation, enabling intelligent matching of component model geometry and semantic information. It facilitates human–machine interaction applications such as AR-based visualization for positioning and verification of pre-embedded components, information querying, and progress simulation. Additionally, the system supports collaborative operations across multiple terminal devices, ensuring information consistency and task synchronization among diverse roles. Its application in the Mingzhu Bay Submerged Tunnel Project in Nansha, Guangzhou, validates the feasibility and practical utility of the proposed workflow in a pilot case, and indicates potential for further validation in broader construction settings. Full article

This study investigates the interlayer properties and sustainability of 3D-printed ultra-high-performance concrete (UHPC) modified with antimony tailings (ATs). The different AT ratios considered were 2.7, 5.4, 8.1, 10.8, and 13.5 wt% additions. The mechanical experiments show the optimal concentration resulting in compressive and flexural strength of 11.2% and 17.2% enhancement at 28 days, respectively. SEM analysis revealed that AT enhances the interlayer strength of 3D-printed UHPC and influences the anisotropic behavior of the matrix around steel fibers. X-CT demonstrated that increasing the AT from the compared group to 13.5% reduced the pore volume from 2.02% to 0.30%. Furthermore, an environmental impact assessment of the 10.8 wt% AT exhibited a 32.5% reduction in key indicators including abiotic depletion (ADP), acidification potential (AP), global warming potential (GWP), and ozone depletion potential (ODP). Consequently, UHPC incorporating AT offers superior environmental sustainability in the practical construction of 3D-printed concrete. This research provides practical guidance in optimizing 3D-printed UHPC engineering, further facilitating the integrated design and manufacturing of multi-layer structures. Full article

In urban underground space construction using shield tunnelling, the geological conditions ahead of the tunnel face are often uncertain. Without timely and accurate classification of the ground type, mismatches in operational parameters, uncontrolled costs, and schedule risks are likely to occur. Using observations from an earth pressure balance (EPB) project on an urban railway, a data-driven classification framework is developed that integrates shield tunnelling operating measurements with physically derived quantities to discriminate among soft soil, hard rock, and mixed strata. Principal component analysis (PCA) is performed on the training set, followed by a systematic comparison of tree-based classifiers and hyperparameter optimization strategies to explore the attainable performance. Under unified evaluation criteria, a categorical bosting (CatBoost) model optimized by a Nevergrad combination strategy (NGOpt) attains the highest test accuracy of 0.9625, with macro-averaged precision and macro-averaged recall of 0.9715 and 0.9716, respectively. To mitigate optimism from single-point estimates, stratified bootstrap intervals are reported for the test set. A Monte Carlo experiment applies independent perturbations to the PCA-transformed features, producing low label-flip rates across the three classes, with only minor changes in probability calibration metrics, which suggests consistent decisions under sensor noise and sampling bias. Overall, within the scope of the considered EPB project, the study delivers a compact workflow that demonstrates the feasibility of uncertainty-aware ground-type classification and provides a methodological reference for developing decision-support tools in underground tunnel construction. Full article

To ensure the safe operation of railway tunnels and prevent methane disasters in auxiliary tunnels, this paper focuses on the post-construction closure of an auxiliary tunnel (cross tunnel) in a railway tunnel with methane presence. Computational Fluid Dynamics (CFD) simulations were employed to investigate methane migration and accumulation patterns under different sealing conditions in railway auxiliary tunnels. The optimal auxiliary tunnel end-face closure method was identified. Subsequently, the influences of factors such as tunnel length and methane concentration on the explosion characteristics were analyzed under the optimal closed process conditions. The results show that after methane escapes from the coal seam, it initially accumulates at the tunnel’s roof and then diffuses downward due to the concentration gradient. When the lower end face of the auxiliary tunnel is opened and the upper end face is sealed, the degree of methane enrichment in the tunnel is the lowest and the enrichment speed is the slowest. Under partial methane conditions, the explosion pressure propagated and released more easily within the tunnel, leading to higher peak pressure. As the length of the tunnel increases, the peak pressure of the explosion increases, and the explosion power becomes greater. The overpressure of the explosion shock wave follows a nonlinear relationship with distance and is inversely proportional to the square root of the distance. The findings provide theoretical guidance for the prevention and control of methane-related accidents and disasters. Full article

Due to its effective noise reduction, the semi-enclosed noise barrier is increasingly being applied in the construction of high-speed railways. However, there is still a lack of systematic research on the wind load distribution characteristics under natural crosswind, especially for the complex aerodynamic behavior of the intersection section of multi-line bridges. Therefore, the wind load distribution characteristics on the surface of the sound barrier under crosswind conditions are explored within the engineering context of a semi-enclosed acoustic barrier at the junction of a single-track bridge and a three-track bridge, using a combination of wind tunnel testing and numerical simulation. A rigid-body model with a geometric scale of 1:10 is established for the wind tunnel test. The wind load distribution characteristics of the two acoustic barriers are analyzed from the perspectives of mean wind pressure, pulsating wind pressure, and extreme wind pressure, respectively. FLUENT 2022 software is utilized to model the flow field characteristics of the sound barrier under two working conditions: windward and leeward. The results show that under the action of crosswind, the surface wind load of the sound barrier at the junction of the single/three-line bridge is very prominent, the maximum negative pressure shape coefficient is −4.516, and its distribution is dominated by negative pressure; that is, the sound barrier mainly bears suction. Compared with the semi-closed sound barrier on the single-track bridge, the extreme wind pressure at the semi-closed sound barrier on the three-track bridge and the junction of the two is more significant, which shows that this kind of area needs special attention in wind-resistant design. Full article

With the comprehensive implementation of the “Belt and Road” initiative and the Western Development Strategy, the scale of tunnel construction has been continuously expanding, with many tunnels being built in high ground stress and fractured soft rock strata. The design, construction, and operation of tunnels all rely on the surrounding rock pressure as a fundamental basis. Therefore, determining the surrounding rock pressure is essential for ensuring the safe construction of tunnels. However, due to the complexity of geological conditions, differences in construction methods, variations in support parameters, and time–space effects, it is challenging to accurately determine the surrounding rock pressure. This paper proposes a design approach using the surrounding rock pressure design value as the “support force” for the tunnel, starting with the reserved deformation of soft rock tunnels. Based on the calculation principle of the surrounding rock pressure design value, a relationship curve between the support force and the maximum deformation of surrounding rock in high ground stress soft rock tunnels is developed. By combining the surrounding rock deformation grade with the tunnel’s reserved deformation index, a calculation method for the surrounding rock pressure design value for high ground stress soft rock tunnels is proposed. The method is verified by the measured surrounding rock pressure data from the Mao County Tunnel of the Chengdu–Lanzhou Railway. Furthermore, the study integrates the creep characteristics and strain softening properties of soft rock to implement a secondary development of the viscoelastic–plastic strain softening mechanical model. Based on a custom-developed creep model and the calculation method for the surrounding rock pressure design value, the relationship among time, support force, and surrounding rock deformation is comprehensively considered. A calculation method for the surrounding rock pressure design value, accounting for time effects, is proposed. Based on this method, a time-history curve of the surrounding rock pressure design value is obtained and used as the input load. The safety factor time evolution of the rock-anchor bearing arch, spray layer, and secondary lining is derived using the load-structure method, and the overall safety factor time evolution of the tunnel support structure is evaluated. The overall stability of the support structure is assessed, and numerical simulations are compared with field measurements based on the mechanical behavior evolution law of the secondary lining of the Chengdu–Lanzhou Railway Mao County Tunnel. The results indicate that the monitoring data of the internal forces of the field support structure is in good agreement with the numerical calculation results, validating the rationality of the proposed calculation method. 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

Due to intensified climate change and increasing extreme wind events, wind–sand and wind–snow compound disasters pose growing threats to the safety, serviceability, and long-term sustainability of railway infrastructure, particularly in arid and cold regions such as Xinjiang. To support sustainable transportation and enhance infrastructure resilience, this study investigates the airflow field characteristics and composite particle transport under different fence configurations through a combination of wind tunnel testing and numerical simulations. The results show that double-row fences significantly reduce particle transport and deposition, improving the long-term stability of railway lines while minimizing maintenance frequency and energy consumption. Orthogonal analysis indicates that fence spacing exerts the strongest influence on composite particle deposition, followed by fence height and porosity. Furthermore, composite sand–snow particles exhibit a synergistically enhanced transport capacity under high wind speeds, highlighting the need for integrated mitigation measures. This study provides practical guidance for designing sustainable, low-impact, and climate-adaptive protection systems in regions facing compound wind-driven hazards, contributing to the broader goals of enhancing infrastructure durability and achieving sustainable regional development. Full article

The rapid development of transportation infrastructure in challenging geological regions necessitates innovative tunneling methods that balance efficiency, safety, and cost. This study addresses the critical construction bottleneck of large-span soft rock tunnels under high ground stress, where conventional methods often lead to unacceptable delays. Focusing on a 24.53 m span railway tunnel in southwest China, we present the significant engineering application of a “pilot-tunnel-first” method as a strategic solution to stringent schedule pressures. The core innovation lies not only in the adoption of a large 13.2 m wide pilot tunnel but also in a synergistically enhanced support system, featuring elongated bolts (6 m and 12 m) and strengthened steel arches. Numerical simulations and field validation confirmed that this optimized approach achieves a stability comparable to the traditional double-side drift method while dramatically accelerating progress. The successful implementation shortened the construction period by 1.96 months for a key 123 m section, with a manageable cost increase of approximately Chinese Yuan (CNY) 782,000, thereby ensuring the timely opening of the entire tunnel. The primary significance of this research is to provide a proven and practical technical strategy for overcoming similar soft rock tunneling challenges where project timelines are paramount, offering a substantial value for the design and construction of modern infrastructure under complex constraints. Full article

Deformation monitoring of heavy-haul railway tunnels is essential for ensuring operational safety. However, the spatial resolution of traditional point-based sensors is often insufficient for capturing the continuous deformation fields of tunnel structures. To overcome this limitation, in this study, densely distributed strain data that are acquired through distributed fiber-optic sensing technology are used, and a deep learning-based inversion framework that integrates high-resolution strain measurements with sparsely sampled convergence data is introduced. By employing a hybrid particle swarm optimization–random forest (PSO-RF) algorithm, a deep correlation model is constructed to establish the relationship between distributed strain profiles and discrete convergence measurements. This approach enables the prediction of cross-sectional convergence across multiple tunnel sections by using only a limited set of calibrated convergence sensors in combination with continuous strain field data, thereby effectively achieving global deformation inversion with minimal hardware deployment. The proposed method was validated through numerical simulations and field tests by using monitoring data from a heavy-haul railway tunnel. The algorithm exhibited a mean absolute error of less than 2 mm, thus demonstrating its ability to supply high-resolution deformation field data that are essential for structural health monitoring and diagnostics of tunnel infrastructures. Full article

Shield tunneling beneath existing railways remains a critical challenge in urban infrastructure development, as it risks destabilizing overlying soil structures and compromising railway safety. This study presents an integrated methodology combining physical model tests and three-dimensional numerical simulation, validated by their mutual agreement, to capture the settlement and deformation induced by twin shield tunneling beneath an operational railway under the complex geological conditions of the Qingdao Metro. A parametric study was subsequently conducted to systematically evaluate the influence of critical construction parameters, including grouting pressure, grout stiffness, and chamber pressure, on railhead settlement. Additionally, a comparative analysis assessed the effectiveness of settlement control measures, including D-type beam reinforcement, deep-hole grouting reinforcement, and their combined application. Results show that railhead deformation primarily manifests as settlement, with cumulative effects from sequential tunneling of the left and right lines. Proximity to fault zones intensifies crown subsidence, while tunneling induces significant soil stress relaxation, particularly in geologically weaker strata. Within optimal ranges, increased grouting pressure, chamber pressure, and grout stiffness effectively reduce railhead settlement; however, their efficacy diminishes beyond specific thresholds. The combined D-type beam and deep-hole grouting reinforcement scheme proved most effective in controlling settlement, ensuring railway operational safety and construction stability. These findings provide essential theoretical and practical guidance for optimizing shield tunneling strategies in complex urban environments, enhancing the safety and reliability of critical railway infrastructure. Full article

This study presents a comprehensive review of the CLH index, a predictive tool developed to estimate the wear of tunnel boring machine (TBM) disc cutters operating in hard rock conditions. The CLH index provides a simplified, time-efficient, and cost-effective alternative to conventional wear prediction methods by employing a statistically derived empirical formula. The methodology is based on the identification and quantitative assessment of key rock properties that influence cutter wear. A detailed statistical analysis was conducted to validate the index, quantify potential errors, and determine confidence levels. As part of this review, updated reference tables are proposed to facilitate cutter wear estimation without the need for preliminary laboratory testing. These tables are derived from empirical data obtained at the Rock Mechanics Laboratory of the Higher Technical School of Mining and Energy Engineers (ETSIME-UPM), using operational records from TBM excavation in multiple Spanish high-speed railway tunnels, with a total length exceeding 120 km. The results confirm the reliability and practical applicability of the CLH index as a decision-support tool in TBM performance forecasting and maintenance planning. Full article