Intelligent decision support for tunnel fire incidents: integrating dynamic knowledge graph with large language models

An elastoplastic analytical method for characterizing the plastic zones around twin circular tunnels excavated at shallow depth

Instability analysis of circumferential and radial yielding structures in high in-situ stress soft rock tunnels based on polyurethane foam

Reliability-informed inverse design of dual tunnels with deep evidential regression

The interaction between surrounding rock and support structure is fundamental for support structure design and tunnel stability evaluation, closely related to underground engineering safety and economy. A strain-softening model based on Unified Strength Criteria (USC) is employed to characterize deep rock masses, considering intermediate principal stress effects on rock mechanical behavior. Under the assumption of axisymmetric plane strain, a new mechanical model for rock-support interaction is established. A corresponding solution method is proposed and validated by numerical simulation results, existing analytical models and field datasets. Parameter studies were conducted to investigate the effects of intermediate principal stress and supporting time on rock-support interaction. The findings indicate that the intermediate principal stress has a significant impact on the stability of the surrounding rock and the load-sharing behavior of the support structure. The increasing intermediate principal stress significantly reduces both tunnel wall displacement and support load, with a Stress Effect Factor (SEF) demonstrating up to a 28.1% reduction in tunnel wall deformation and a 12.6% reduction in support load when transitioning from the traditional Mohr-Coulomb criterion (the intermediate principal stress effect coefficient b =0) to a double shear strength criterion ( b =1). The proposed model and solution method provide a comprehensive and accurate approach to analyzing rock-support interaction in deep tunnels, offering valuable insights for tunnel design and support structure optimization.

To reveal the regional differentiation characteristics of carbon emissions during the construction phase of expressways and to improve prediction accuracy, six typical expressway projects located in the plain, hilly, and mountainous regions of Anhui Province were selected as case studies. A carbon emission accounting model for the construction phase was established based on the life cycle assessment method, and the effects of the bridge-tunnel ratio, subproject structure, and material and energy consumption on carbon emission intensity were systematically analyzed. On this basis, a regional carbon emission prediction model was developed and optimized using data from 21 completed expressways across the province. The results indicate that carbon emission intensity exhibits a significant topographic gradient, with mountainous regions showing higher values than hilly regions, and hilly regions higher than plain regions. The maximum carbon emission intensity in mountainous projects reaches 5.27 × 10⁷ kg CO₂/km, which is 2.86 times that of plain regions. As terrain complexity increases, the carbon emission structure shifts from being dominated by subgrade engineering and interchange engineering to being dominated by structural engineering, such as bridges and tunnels. In mountainous regions, emissions from structural engineering account for more than 50% of the total emissions. At the material level, cement and steel are identified as the primary emission sources, jointly accounting for 78% of total emissions in mountainous projects, and demonstrating the highest sensitivity to variations in total emissions. The prediction results show that the baseline model using the bridge-tunnel ratio as a single variable achieves a coefficient of determination (R²) of 0.69. After incorporating material and energy consumption variables, the optimized XGBoost model improves the coefficient of determination to 0.9517, achieving high-accuracy prediction using only eight categories of material and energy consumption indicators. Based on the analytical results, differentiated emission reduction pathways are proposed. In mountainous regions, priority should be given to optimizing the design of tunnels and interchange engineering and controlling the intensity of high-carbon structural materials. In plain and hilly regions, emphasis should be placed on low-carbon design and construction optimization of bridge and culvert engineering and subgrade engineering. This study provides a data-driven basis for regional carbon emission prediction and emission reduction decision-making during the construction phase of expressways.

Currently, the classification of weathered degrees in granite surrounding rock of subsea tunnels primarily relies on preliminary methods such as field characteristic observation, rock sample compressive strength test and wave velocity test. These approaches offer limited accuracy and yield relatively coarse classification results, which can lead to misjudgments regarding rock stability during tunnel design and construction. As a result, weak surrounding rock areas that should have been treated with grouting reinforcement may be overlooked, increasing the risk of tunnel face collapse or water inrush. Based on the weathering characteristics of granite surrounding rock of subsea tunnels with different weathered degrees along the southeastern coast of China, this study aims to provide a more reliable basis for the refined classification of surrounding rock, thereby helping to avoid the occurrence of such engineering accidents. The mechanical properties of weathered granite were evaluated through uniaxial compressive and triaxial compression tests. Then, the polarizing microscopy and the X-ray Computed Tomography (X-ray CT) were employed to obtain the variations in microstructural parameters of weathered granite. Subsequently, X-ray diffraction (XRD) analysis was performed to examine the mineral composition of granite with varying degrees of weathering. The results indicate that weathering not only reduces the mechanical strength of the granite surrounding rock but also increases its porosity. Additionally, the content of clay minerals within the granite surrounding rock continuously increases with the degree of weathering, particularly in completely weathered granite, where clay minerals dominate the composition. This further causes the surrounding rock structure to loosen, increasing the number of pores and ultimately reducing the overall strength and stability of the surrounding rock. Finally, the mathematical relationships between the mechanical parameters, pore fractal dimension, and clay mineral content were established to quantitatively characterize the weathering effect of granite surrounding rock. These results could serve as reference for the construction of subsea tunnels crossing weathered granite strata.

Hydraulic regime transitions and localized backwater responses can develop in gently sloped tunnels when shafts and short expansion–contraction transitions act as localized hydraulic controls. This study investigates a tunnel–shaft system using a combined theoretical, numerical, and experimental framework. A momentum-based spreadsheet model was first used to identify the discharge range at which backwater development and unsteady behavior begin. The analysis was then extended with EPA–SWMM to represent system-scale unsteady behavior and with a finite element model to resolve local hydraulic gradients near the transition. Numerical results were compared with observations from a Froude-scaled physical model. All approaches consistently showed that backwater develops primarily upstream of the shaft and that the most critical hydraulic zone is concentrated at the geometric discontinuity. A regulated entrance geometry was then evaluated as a mitigation measure. For the case analyzed, entrance regulation reduced inlet depth from 6.12 m to 3.50 m and relative filling from y/D = 0.87 to y/D = 0.503, shifting operation toward a lower-depth operating state with greater freeboard and reduced susceptibility to pressurization. The results demonstrate that shaft transitions should be explicitly considered in tunnel design and that entrance regulation can materially improve hydraulic performance.

Objective This study aims to systematically investigate how key geometric parameters of spiral tunnels, specifically tunnel length and radius and travel direction, influence drivers saccadic eye movements and visual load. Methods A field experiment was conducted using a wearable eye tracker to record saccadic behavior from 30 licensed drivers. Participants drove through 3spiral tunnels with varying lengths and radii under both uphill and downhill traversal conditions. Four saccade metrics (amplitude, duration, frequency, and velocity) were analyzed using descriptive statistics and ANOVA to evaluate visual workload. These metrics have been selected because they collectively reflect distinct aspects of visual scanning behavior: amplitude indicates the breadth of visual search, duration reflects the time required for processing fixated information, frequency represents the rate of gaze shifting, and velocity denotes the efficiency of oculomotor movement. Results The findings indicate that tunnel geometry and travel direction significantly affect saccadic dynamics. Longer tunnels and smaller radii resulted in increased saccade amplitude, prolonged duration elevated frequency, and reduced velocity, suggesting heightened visual processing demand. Furthermore uphill traversal consistently produced larger amplitudes, longer durations higher frequencies, and slower velocities than downhill traversal across all tunnels, revealing a directional asymmetry in visual load. Conclusions This study demonstrates that spiral tunnel design, especially extended length and reduced radius, elevates drivers’ visual cognitive load with uphill travel imposing greater demands. The results provide empirical evidence to inform geometry-based design guidelines for optimizing visual ergonomics and improving operational safety in spiral tunnels.

Abstract With the rapid expansion of metro networks in China, the cumulative length of shield tunnels constructed in soft soil has exceeded 6000 km. While extensive engineering experience has been accumulated, these tunnels are still increasingly affected by service-related issues, such as long-term settlement, deformation, structural damage, and water leakage. These defects impose challenges to both operational safety and maintenance costs. This study provides a systematic overview of the major defect types and their spatial distribution patterns, highlighting their implications for the resilience and safety of shield tunnels. The coupled development and interaction of these defects are analyzed, and the limitations of existing research methodologies are critically examined. Based on these findings, this paper introduced a novel load mode to consider service tunnel’s environmental load variations, thereby proposing insights for enhancing the resilience of shield tunnel design from the tunnel–soil interaction perspective. Meantime, an elastic–plastic resistance model is also developed to address the degradation of lateral resistance at the tunnel waist caused by the fluidity of soft soils. A mathematical formulation of system stiffness is further developed by treating the tunnel and soil as an integrated system. Building upon this formulation, a resilience‑based design method is proposed to ensure the resilient performance of shield tunnels throughout the entire life cycle. The method is validated through its application to the Foshan and Shaoxing metro systems, with results demonstrating that optimizing system stiffness can significantly improve the resilience of shield tunnel structures in soft soils.

Deep-buried tunnels in urban environments require careful evaluation of their long-term interactions with the surrounding ground to ensure structural safety and sustainability. Taking the Beijing Eastern Sixth Ring Road renovation project as a case study, this research employs a fully coupled fluid–solid numerical approach to elucidate the long-term disturbance mechanisms associated with deep-buried shield tunneling. Specifically, the research quantifies spatio-temporal ground responses and characterizes the consolidation settlement mechanisms exacerbated by potential tunnel leakage. The results indicate that ground deformation is primarily governed by the intensity of tunnel leakage. When the waterproofing grade of the tunnel meets Grade I or II, leakage and surface settlement remain negligible. However, when a tunnel’s waterproofing grade deteriorates to Grade IV or lower, consolidation settlement increases significantly, becoming the dominant deformation mode. In addition, both the extent and severity of ground movement are highly sensitive to the geometrical boundaries of the strata and the relative depth of the tunnel. Larger permeable domains and deeper tunnels lead to wider pore pressure and stress disturbance zones, ultimately leading to more pronounced long-term settlement. Furthermore, soil permeability dictates the temporal evolution of the ground response, with poorly permeable layers exhibiting delayed fluid–solid re-equilibration. A critical threshold is observed when leakage rates align with or exceed the soil’s permeability, leading to a significant escalation in both the amplitude of subsidence and the time required to reach equilibrium. These findings offer valuable insights for the design, waterproofing, and long-term management of deep urban tunnels.

Tunnel reliability analysis is an important analytical method to ensure tunnel safety. In this paper, the plane elastic complex variable function theory is adopted, and the explicit displacement function of the horseshoe-shaped tunnel vault is derived through conformal mapping. This function is verified by ABAQUS numerical analysis, and the correctness of the derivation is further confirmed by degenerating it to a circular tunnel. Subsequently, based on this explicit displacement function, a comparative analysis is conducted on four methods: the advanced first-order second moment (AFORM) method, Monte Carlo sampling (MCS) method, importance sampling (IS) method, and radial-based importance sampling (RBIS) method. The results show that the RBIS method has higher calculation accuracy and better efficiency. Finally, considering the influences of the mean value of load, load variation coefficient, and surrounding rock parameters, the reliability of the horseshoe-shaped tunnel and the circular tunnel is compared and analyzed based on the derived explicit function. It is found that except for the lateral pressure coefficient, the two types of tunnels are similar in terms of the sensitivity of other parameters and the influence laws of parameters on reliability. The research results can provide a reference for the analogical design and analysis of horseshoe-shaped tunnels and circular tunnels.

Purpose The carbon emission intensity of tunnel projects is highly dependent on design schemes, making carbon management during the design phase a challenge. Although existing research on design-oriented carbon emission management has made notable progress, it remains fragmented and lacks a systematic overview. This article reviews current studies, identifies major research gaps and proposes improvement pathways to support tunnel decarbonization. Design/methodology/approach This study uses a systematic literature review following PRISMA guidelines to analyze 60 core publications on carbon emission management in tunnel design. Findings Current research on carbon emission management in tunnel engineering design focuses on assessment methods, low-carbon design elements, optimization of carbon emissions in design schemes and emission reduction strategies. However, it identifies four major limitations: a lack of uncertainty analysis in assessment methods, insufficient research on the coupling mechanism of low-carbon design elements, absence of dynamic optimization for the entire lifecycle and weak adaptability of emerging technologies. To address these challenges, a new framework for carbon emission management in tunnel engineering design is proposed, based on “intelligent perception-regulation optimization-negative carbon conversion.” Originality/value The study proposes a carbon emission management framework for tunnel engineering design based on “intelligent perception-regulation optimization-negative carbon conversion,” not only fills structural gaps in the theoretical system of low-carbon design for tunnel engineering but also provides practical decision-making tools for engineering practice, enabling a negative growth in total carbon emissions while maintaining engineering efficiency.

Reliability analysis of 1D estimation for TBM operational parameters

This study investigates the influence of tunnel span on the dynamic response of rock masses with high integrity under intense dynamic load, analyzing an unlined circular tunnel excavated in intact surrounding rock with a uniaxial compressive strength of fr=57 MPa. Using a combined approach of physical model testing and numerical simulation, the influence mechanism of span on tunnel stability under different intense dynamic loads is systematically analyzed. The research results indicate the following: (1) When the peak intense Dynamic load is below 0.51fr, the surrounding rock mass remains in an elastic state. (2) When the peak load ranges between 0.51fr and 0.54fr, plastic zones emerge at the tunnel wall. (3) Once the peak load exceeds 0.70fr, the influence of the tunnel span on stability becomes significantly more pronounced with increasing load intensity. In small-span tunnels, plastic zones primarily distribute along the wall sides, whereas in large-span tunnels, they extend further upward and downward. (4) At a peak load of 0.70fr, the ratio of the maximum extent of the plastic zone in a 20 m span tunnel to that in a 5 m span tunnel is 10.70, and the ratio of the maximum relative displacement between the vault and invert is 4.67. When the peak load increases to 1.40fr, the plastic zone extent ratio rises to 13.94, and the vault–invert displacement ratio increases to 6.17. The conclusions of this study provide theoretical foundations for the design of tunnels with varying spans under intense dynamic load.

This study systematically investigates the damage characteristics of tunnels under reverse fault dislocation through the establishment of a three-dimensional finite element model for fault-surrounding rock-tunnel interaction, employing non-uniform seismic motion input. The research focuses on analyzing the influence of dislocation displacement, fault zone width, and fault dip angle on damage evolution patterns. The results indicate that: (1) Tunnel damage is predominantly concentrated in the fault core zone, with stress concentration frequently occurring at the haunch areas. Fault displacement constitutes the primary causative factor for tunnel damage. (2) Increased dislocation displacement exacerbates structural damage, exhibiting asymmetric propagation along the axial direction from the fault core; (3) Fault zone width affects stiffness transition gradients, where greater width enhances deformation coordination capacity and mitigates overall lining failure; (4) Under high-dip-angle conditions, particular attention must be paid to axial deformation failure in tunnel structures. The study proposes a novel input methodology, with results providing theoretical references for seismic design of cross-fault tunnels.

ABSTRACT This study develops a reliability‐based framework for predicting and optimizing tunnel stability in rock masses under surcharge loading while explicitly accounting for both aleatory and epistemic uncertainties. A unified dataset for twin circular and square tunnels is generated using Adaptive Finite Element Limit Analysis under the generalized Hoek–Brown criterion. The results demonstrate that probabilistic predictions obtained using Natural Gradient Boosting provide accurate stability estimates together with well‐calibrated uncertainty bounds, consistently outperforming multiple baseline machine‐learning models. Validation against more than 300 independent Optum G2 simulations confirms strong agreement with numerical benchmarks. A dedicated uncertainty decomposition analysis further shows that neglecting either input uncertainty or model uncertainty can lead to misleading and potentially unsafe reliability estimates, underscoring the necessity of joint uncertainty propagation. Overall, the proposed framework enables robust, uncertainty‐aware tunnel design under reliability constraints and provides a practical decision‐support tool for rock engineering applications.

Tunnels of large water conveyance projects often cross active faults and are therefore exposed to permanent ground deformation induced by normal fault dislocation. In this study, a three-dimensional multi-field coupling model is developed to investigate the mechanical response and failure mechanism of a water conveyance tunnel crossing a normal fault. The model integrates surrounding rock, fault fracture zone, reinforced concrete lining, and internal pressurised water through an ABAQUS–FLUENT–MpCCI framework. The surrounding rock and fault zone are described by a Mohr–Coulomb elastoplastic model, the lining is simulated using the concrete damage plasticity model, and the internal water flow is governed by the Reynolds-averaged Navier–Stokes equations with the RNG k–ε turbulence model. The numerical model is qualitatively validated against a scaled physical model test of a tunnel crossing a normal fault, focusing on the localisation of deformation and damage in the fault zone. A systematic parametric analysis is then conducted to examine the influence of fault displacement, fault dip angle, fault zone width, fault cohesion and lining strength. The overall lining damage in tension (OLDT) index is adopted to quantify the global damage state of the lining. The results show that normal fault dislocation induces strongly localised deformation and damage within the fault fracture zone, whereas tunnel segments far away remain essentially elastic. The crown and invert near the fault are confirmed to be the most vulnerable regions due to combined bending and shear. Increasing fault displacement significantly amplifies the lining damage in the fault zone, while variations in fault dip angle and fault width mainly affect the axial extent of the highly deformed region. Higher fault cohesion and higher lining strength both reduce the OLDT value and shrink the severely damaged zone. The internal water slightly modifies the stress distribution in the lining through fluid–structure interaction but does not change the fundamental failure mode. These findings provide a basis for performance-based design and mitigation measures for water conveyance tunnels crossing normal faults.

Theoretical analysis of Seepage Field in Two Supported Circular Tunnels within Anisotropic Ground

Design and construction of an ultra-high temperature wind tunnel for transpiration cooling research