Pub Date : 2026-01-06DOI: 10.1016/j.tust.2025.107430
Simone L. Markus, Mark S. Diederichs
Estimation of groundwater inflow is essential for tunnel design and construction; however, analytical solutions used in current engineering practice have limited applicability, especially in cases where drawdown of the water table occurs due to excavation associated drainage. Existing methods for estimating steady state groundwater inflow under a drawn-down water table require improvement, as they typically assume fixed water table boundaries. This article unites and compares classical inflow formulations and reviews their applicability and limitations. Based on numerical modelling, the study proposes two novel methods for estimating inflow into tunnels based on drawdown: one for inflow into shallow tunnels where full drawdown of the water table occurs (trench-like inflow), and one for inflow into moderately deep tunnels, where partial drawdown of the water table occurs. The inflow-drawdown relationship devised accounts for the influence of tunnel size and depth on drawdown shape, and is independent of assumptions of boundary conditions, which limit applicability of other equations. Additionally, practical guidance for numerical modelling of tunnels below the water table is provided, including sensitivity analysis of boundary conditions.
{"title":"Groundwater inflow into tunnels: semi-empirical methods for estimating steady state inflow associated with excavation induced drawdown","authors":"Simone L. Markus, Mark S. Diederichs","doi":"10.1016/j.tust.2025.107430","DOIUrl":"10.1016/j.tust.2025.107430","url":null,"abstract":"<div><div>Estimation of groundwater inflow is essential for tunnel design and construction; however, analytical solutions used in current engineering practice have limited applicability, especially in cases where drawdown of the water table occurs due to excavation associated drainage. Existing methods for estimating steady state groundwater inflow under a drawn-down water table require improvement, as they typically assume fixed water table boundaries. This article unites and compares classical inflow formulations and reviews their applicability and limitations. Based on numerical modelling, the study proposes two novel methods for estimating inflow into tunnels based on drawdown: one for inflow into shallow tunnels where full drawdown of the water table occurs (trench-like inflow), and one for inflow into moderately deep tunnels, where partial drawdown of the water table occurs. The inflow-drawdown relationship devised accounts for the influence of tunnel size and depth on drawdown shape, and is independent of assumptions of boundary conditions, which limit applicability of other equations. Additionally, practical guidance for numerical modelling of tunnels below the water table is provided, including sensitivity analysis of boundary conditions.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107430"},"PeriodicalIF":7.4,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145903168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-06DOI: 10.1016/j.tust.2025.107402
Fengqiang Gong , Zhixuan Zhang , Bo Wang , Jinhao Dai , Pengyu Ma
Rockburst persistently challenge the safe construction of large-section hard rock tunnels under high geostress environments. At present, the insufficient adaptability of conventional active support strategy which is “Excavate First and Then Support” (EFTS) has limitations in the prevention of the dynamic damage of rockburst. To address the limitations of rockburst prevention, this study proposes a “Proactive-Prevention and Post-Resistant” support (PPS) method for dynamic stability control, which consists of two consecutive steps. First, an initial tunnel with reduced diameter is excavated, followed by installation of pre-stressed rockbolt beyond the designed profile to establish an advanced pressure arch. Subsequently, the tunnel is expanded to the designed cross-section with supplementary reinforcement measures. This new strategy collaboratively combines the stress redistribution effect caused by the initial tunnel geometry, thereby alleviating the degradation of surrounding rock strength caused by excavation and improving the stability of the rock mass. In addition, this strategy takes advantage of the energy absorption capacity of pre-stressed anchor rods, effectively suppressing the risks associated with instantaneous energy release. A case study was conducted on the diversion tunnel No.3 of the Jinping II hydropower station. The evolution of advanced pressure arch boundaries under varying initial tunnel diameters was systematically investigated, as well as the effectiveness of the PPS method. Validation results demonstrate that compared to EFTS support strategy, the PPS method significantly reduces rockburst intensity from widespread moderate to severe rockburst to none or minor rockburst. Mechanistic analysis confirms that this strategy effectively minimizes tangential stress concentration by optimizing pressure arch geometry while enhancing energy dissipation efficiency. The PPSmethod provides a new perspective and methodology for rockburst mitigation in deep large-section hard rock tunnels.
{"title":"A “Proactive-Prevention and Post-Resistant” support method for alleviating rockburst in deep-buried large-section tunnels","authors":"Fengqiang Gong , Zhixuan Zhang , Bo Wang , Jinhao Dai , Pengyu Ma","doi":"10.1016/j.tust.2025.107402","DOIUrl":"10.1016/j.tust.2025.107402","url":null,"abstract":"<div><div>Rockburst persistently challenge the safe construction of large-section hard rock tunnels under high geostress environments. At present, the insufficient adaptability of conventional active support strategy which is “Excavate First and Then Support” (EFTS) has limitations in the prevention of the dynamic damage of rockburst. To address the limitations of rockburst prevention, this study proposes a “Proactive-Prevention and Post-Resistant” support (PPS) method for dynamic stability control, which consists of two consecutive steps. First, an initial tunnel with reduced diameter is excavated, followed by installation of pre-stressed rockbolt beyond the designed profile to establish an advanced pressure arch. Subsequently, the tunnel is expanded to the designed cross-section with supplementary reinforcement measures. This new strategy collaboratively combines the stress redistribution effect caused by the initial tunnel geometry, thereby alleviating the degradation of surrounding rock strength caused by excavation and improving the stability of the rock mass. In addition, this strategy takes advantage of the energy absorption capacity of pre-stressed anchor rods, effectively suppressing the risks associated with instantaneous energy release. A case study was conducted on the diversion tunnel No.3 of the Jinping II hydropower station. The evolution of advanced pressure arch boundaries under varying initial tunnel diameters was systematically investigated, as well as the effectiveness of the PPS method. Validation results demonstrate that compared to EFTS support strategy, the PPS method significantly reduces rockburst intensity from widespread moderate to severe rockburst to none or minor rockburst. Mechanistic analysis confirms that this strategy effectively minimizes tangential stress concentration by optimizing pressure arch geometry while enhancing energy dissipation efficiency. The PPSmethod provides a new perspective and methodology for rockburst mitigation in deep large-section hard rock tunnels.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107402"},"PeriodicalIF":7.4,"publicationDate":"2026-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145928419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-05DOI: 10.1016/j.tust.2025.107311
Kang Fu , Yiguo Xue , Daohong Qiu , Fanmeng Kong , Jianning Wang
Accurate and dynamic identification of surrounding rock grades in TBM tunnels is crucial for ensuring excavation safety and improving construction efficiency. This study proposes a hybrid modeling method based on a physics-data dual-driven approach to achieve high-precision dynamic identification of surrounding rock grades. First, the Isolation Forest model is employed to eliminate outliers from the raw tunneling data, and the key tunneling parameters influencing rock grades are identified using mutual information. Then, the Seasonal and Trend decomposition using LOESS (STL) model is used to perform multimodal decomposition on the dominant tunneling parameters, obtaining the corresponding trend, periodic, and residual components. Subsequently, an Improved Refined Composite Multiscale Sample Entropy (IRCMSE) model is adopted to calculate the feature entropy of each component, forming a dynamic sample database for the data-driven model. Based on this, an improved Convolutional Neural Network – Long Short-Term Memory (CNN-LSTM) model is developed to realize data-driven dynamic identification of TBM tunnel strata. Furthermore, a variation identification formula for surrounding rock grades was proposed based on the principle of geological continuity, enabling physics-driven dynamic identification of surrounding rock grades in TBM tunnels. On this basis, a fusion method combining the physical-driven model and the data-driven model is proposed. The constructed physics-data dual-driven model achieves average precision, recall, F1-score, and accuracy of 98.29 %, 97.98 %, 98.13 %, and 98.30 %, respectively, representing an average improvement of 2.17 % over the data-driven model and 15.07 % over the physical-driven model. Engineering validation results indicate that the overall performance of the model decreases by only 1.74 % and 5.29 % under similar and different geological conditions, respectively, demonstrating strong generalization and robustness, and meeting the requirements of intelligent TBM tunneling under complex geological conditions.
{"title":"Dynamic prediction of surrounding rock grades in TBM tunnels based on physics–data dual-driven model","authors":"Kang Fu , Yiguo Xue , Daohong Qiu , Fanmeng Kong , Jianning Wang","doi":"10.1016/j.tust.2025.107311","DOIUrl":"10.1016/j.tust.2025.107311","url":null,"abstract":"<div><div>Accurate and dynamic identification of surrounding rock grades in TBM tunnels is crucial for ensuring excavation safety and improving construction efficiency. This study proposes a hybrid modeling method based on a physics-data dual-driven approach to achieve high-precision dynamic identification of surrounding rock grades. First, the Isolation Forest model is employed to eliminate outliers from the raw tunneling data, and the key tunneling parameters influencing rock grades are identified using mutual information. Then, the Seasonal and Trend decomposition using LOESS (STL) model is used to perform multimodal decomposition on the dominant tunneling parameters, obtaining the corresponding trend, periodic, and residual components. Subsequently, an Improved Refined Composite Multiscale Sample Entropy (IRCMSE) model is adopted to calculate the feature entropy of each component, forming a dynamic sample database for the data-driven model. Based on this, an improved Convolutional Neural Network – Long Short-Term Memory (CNN-LSTM) model is developed to realize data-driven dynamic identification of TBM tunnel strata. Furthermore, a variation identification formula for surrounding rock grades was proposed based on the principle of geological continuity, enabling physics-driven dynamic identification of surrounding rock grades in TBM tunnels. On this basis, a fusion method combining the physical-driven model and the data-driven model is proposed. The constructed physics-data dual-driven model achieves average precision, recall, F1-score, and accuracy of 98.29 %, 97.98 %, 98.13 %, and 98.30 %, respectively, representing an average improvement of 2.17 % over the data-driven model and 15.07 % over the physical-driven model. Engineering validation results indicate that the overall performance of the model decreases by only 1.74 % and 5.29 % under similar and different geological conditions, respectively, demonstrating strong generalization and robustness, and meeting the requirements of intelligent TBM tunneling under complex geological conditions.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107311"},"PeriodicalIF":7.4,"publicationDate":"2026-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145897494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-04DOI: 10.1016/j.tust.2025.107362
Rui Zhan, Bo Zhang, Lang Liu, Chao Huan, Huisheng Qu, Huicong Xu, Jin Zhang, Hongjun Xi
The utilization of goafs for building high-temperature thermal energy storage cavities is an effective approach to large-scale solar thermal energy storage. However, its long-term stability is constrained by the damage evolution and crack propagation of the backfill body under thermo-mechanical coupling effects. To address this, this study establishes a thermo-mechanical-damage coupled model based on elastic damage theory to describe the damage behavior of the backfill body under thermal expansion effects. Damage evolution is jointly governed by the maximum tensile stress criterion and the Drucker-Prager criterion. The model’s accuracy is validated through numerical simulations, high-temperature uniaxial compression tests on backfill bodies, and comparisons with analytical solutions. Based on this model, the crack propagation and damage evolution patterns during long-term operation of the thermal energy storage cavity are investigated. Results indicate that the circular thermal energy storage cavity, due to its axisymmetric structure, facilitates a uniform distribution of thermal stresses. Radial thermal expansion is converted into uniform circumferential stresses, thereby reducing local stress concentrations. Storage temperature is a key factor controlling backfill body damage. The damage growth rate reaches as much as 56.8 % in the high-temperature range of 400 °C to 450 °C, significantly higher than the 16.8 % growth rate observed between 300 °C and 350 °C. Under low vertical stress conditions, damage zones in the backfill body remain controllable without crack propagation. Conversely, high vertical stress induces coupling between stress concentration and the thermal softening effect, leading to tensile damage at the top and bottom of the thermal energy storage cavity and ultimately resulting in crack formation. Furthermore, maintaining a spacing between adjacent thermal energy storage cavities on the same level that exceeds 1.5 times the cavity diameter effectively mitigates the risk of overall instability caused by the interconnection of damage zones. This study provides theoretical foundations and technical references for the safe design of high-temperature thermal energy storage cavities in mine goaf areas.
{"title":"A numerical study of damage evolution and crack propagation in backfill bodies of high-temperature thermal energy storage cavities in mines","authors":"Rui Zhan, Bo Zhang, Lang Liu, Chao Huan, Huisheng Qu, Huicong Xu, Jin Zhang, Hongjun Xi","doi":"10.1016/j.tust.2025.107362","DOIUrl":"10.1016/j.tust.2025.107362","url":null,"abstract":"<div><div>The utilization of goafs for building high-temperature thermal energy storage cavities is an effective approach to large-scale solar thermal energy storage. However, its long-term stability is constrained by the damage evolution and crack propagation of the backfill body under thermo-mechanical coupling effects. To address this, this study establishes a thermo-mechanical-damage coupled model based on elastic damage theory to describe the damage behavior of the backfill body under thermal expansion effects. Damage evolution is jointly governed by the maximum tensile stress criterion and the Drucker-Prager criterion. The model’s accuracy is validated through numerical simulations, high-temperature uniaxial compression tests on backfill bodies, and comparisons with analytical solutions. Based on this model, the crack propagation and damage evolution patterns during long-term operation of the thermal energy storage cavity are investigated. Results indicate that the circular thermal energy storage cavity, due to its axisymmetric structure, facilitates a uniform distribution of thermal stresses. Radial thermal expansion is converted into uniform circumferential stresses, thereby reducing local stress concentrations. Storage temperature is a key factor controlling backfill body damage. The damage growth rate reaches as much as 56.8 % in the high-temperature range of 400 °C to 450 °C, significantly higher than the 16.8 % growth rate observed between 300 °C and 350 °C. Under low vertical stress conditions, damage zones in the backfill body remain controllable without crack propagation. Conversely, high vertical stress induces coupling between stress concentration and the thermal softening effect, leading to tensile damage at the top and bottom of the thermal energy storage cavity and ultimately resulting in crack formation. Furthermore, maintaining a spacing between adjacent thermal energy storage cavities on the same level that exceeds 1.5 times the cavity diameter effectively mitigates the risk of overall instability caused by the interconnection of damage zones. This study provides theoretical foundations and technical references for the safe design of high-temperature thermal energy storage cavities in mine goaf areas.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107362"},"PeriodicalIF":7.4,"publicationDate":"2026-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.tust.2025.107411
Hao Cui , Jian Li , Qingwu Hu , Long He , Yiwen Tao , Lei Xu , Qingzhou Mao
Tunnels are critical infrastructure, the surface reconstruction of their point cloud is essential for applications such as reality capture BIM and digital twin systems. While mobile mapping systems (MMS) represent an efficient approach for acquiring tunnel point clouds, existing surface reconstruction methods suffer from low efficiency and poor geometric fidelity in tunnel environments. This paper proposes TTM (topology transfer meshing), a concise yet efficient surface reconstruction method for MMS-acquired tunnel point clouds. The approach employs an occlusion-free projection to map 3D point clouds onto a 2D plane, constructs a 2D Delaunay triangulation, and subsequently transfers the mesh topology back to 3D space through a topology transfer mechanism. Qualitative and quantitative experiments conducted on point cloud datasets totaling over 6 km of subway, high-speed rail, and highway tunnels, comprising more than 1 billion points, demonstrate that our method outperforms both conventional and deep learning-based surface reconstruction approaches in both computational efficiency and geometric fidelity. Additional experiments confirm the method’s robust meshing capability with decimated point clouds while revealing heightened sensitivity to point clouds containing substantial measurement errors. Beyond tunnel engineering, this technique extends to digital modeling of linear infrastructure, including pipelines and utility tunnels, providing efficient technical support for intelligent operation and maintenance.
{"title":"TTM: A concise yet effective surface reconstruction approach for tunnel point cloud from mobile mapping system","authors":"Hao Cui , Jian Li , Qingwu Hu , Long He , Yiwen Tao , Lei Xu , Qingzhou Mao","doi":"10.1016/j.tust.2025.107411","DOIUrl":"10.1016/j.tust.2025.107411","url":null,"abstract":"<div><div>Tunnels are critical infrastructure, the surface reconstruction of their point cloud is essential for applications such as reality capture BIM and digital twin systems. While mobile mapping systems (MMS) represent an efficient approach for acquiring tunnel point clouds, existing surface reconstruction methods suffer from low efficiency and poor geometric fidelity in tunnel environments. This paper proposes TTM (topology transfer meshing), a concise yet efficient surface reconstruction method for MMS-acquired tunnel point clouds. The approach employs an occlusion-free projection to map 3D point clouds onto a 2D plane, constructs a 2D Delaunay triangulation, and subsequently transfers the mesh topology back to 3D space through a topology transfer mechanism. Qualitative and quantitative experiments conducted on point cloud datasets totaling over 6 km of subway, high-speed rail, and highway tunnels, comprising more than 1 billion points, demonstrate that our method outperforms both conventional and deep learning-based surface reconstruction approaches in both computational efficiency and geometric fidelity. Additional experiments confirm the method’s robust meshing capability with decimated point clouds while revealing heightened sensitivity to point clouds containing substantial measurement errors. Beyond tunnel engineering, this technique extends to digital modeling of linear infrastructure, including pipelines and utility tunnels, providing efficient technical support for intelligent operation and maintenance.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107411"},"PeriodicalIF":7.4,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145894673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.tust.2025.107425
Zhi Ding , Chaofeng Chen , Yang Chen , Honglei Sun , Hai Xia , Zhenhua Chen , Xiao Zhang
The single-tube double-track underwater tunnel has gained prominence in recent years due to its practicality. Given the unique structural configuration, systematic investigation into the dynamic responses of this type of tunnels under train loads holds substantial practical value. This study adopts a technical route combining physical model testing and numerical simulation, conducting systematic research on the coupled scenario of “high water pressure–high-speed train load–large-diameter tunnel–single-tube double-track”. Peak particle acceleration (PPA) and frequency response function (FRF) were employed as key indicators to evaluate dynamic behavior. The results indicated that higher train speeds elevated the intensity of dynamic response magnitude along the segments, while the overall shape of the envelope remained consistent. Additionally, key response quantities (e.g., PPA and excess PWP) in the surrounding soil increased with train speed, showing nonlinear variation characteristics, with higher values observed in the upper and lower zones. While initial saturation amplified the dynamic response compared to dry conditions, both the peak acceleration and displacement were suppressed as hydrostatic water pressure increased. The similar suppressive effect was observed in the excess PWP response (whether overall magnitude or oscillations induced by train loads) of soil, possibly due to the additional lateral constraint effects. Compared to unidirectional loading, bidirectional loading notably increased the peak acceleration response and fluctuation amplitude of internal forces in the tunnel structure as well as the excess PWP response in the surrounding soil, while the magnitudes of these increases varied across different locations. Meanwhile, stress and strain responses in the surrounding soil concentrated primarily above and below the tunnel during the meeting of train crossings. The findings of this study provide insights for the construction and design of single-tube double-track underwater tunnel.
{"title":"Dynamic response of an underwater single-tube double-track tunnel under high-speed train loads: experimental and numerical investigation","authors":"Zhi Ding , Chaofeng Chen , Yang Chen , Honglei Sun , Hai Xia , Zhenhua Chen , Xiao Zhang","doi":"10.1016/j.tust.2025.107425","DOIUrl":"10.1016/j.tust.2025.107425","url":null,"abstract":"<div><div>The single-tube double-track underwater tunnel has gained prominence in recent years due to its practicality. Given the unique structural configuration, systematic investigation into the dynamic responses of this type of tunnels under train loads holds substantial practical value. This study adopts a technical route combining physical model testing and numerical simulation, conducting systematic research on the coupled scenario of “high water pressure–high-speed train load–large-diameter tunnel–single-tube double-track”. Peak particle acceleration (PPA) and frequency response function (FRF) were employed as key indicators to evaluate dynamic behavior. The results indicated that higher train speeds elevated the intensity of dynamic response magnitude along the segments, while the overall shape of the envelope remained consistent. Additionally, key response quantities (e.g., PPA and excess PWP) in the surrounding soil increased with train speed, showing nonlinear variation characteristics, with higher values observed in the upper and lower zones. While initial saturation amplified the dynamic response compared to dry conditions, both the peak acceleration and displacement were suppressed as hydrostatic water pressure increased. The similar suppressive effect was observed in the excess PWP response (whether overall magnitude or oscillations induced by train loads) of soil, possibly due to the additional lateral constraint effects. Compared to unidirectional loading, bidirectional loading notably increased the peak acceleration response and fluctuation amplitude of internal forces in the tunnel structure as well as the excess PWP response in the surrounding soil, while the magnitudes of these increases varied across different locations. Meanwhile, stress and strain responses in the surrounding soil concentrated primarily above and below the tunnel during the meeting of train crossings. The findings of this study provide insights for the construction and design of single-tube double-track underwater tunnel.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107425"},"PeriodicalIF":7.4,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-03DOI: 10.1016/j.tust.2025.107427
Zhinan Hu , Yuejian Wang , Shaobo Qin , Shunde Yin , Haiyang Pan , Kaimeng Ma
The mechanical performance of segmental joints in semi-rigid element immersed tunnels is influenced significantly by differential settlement. The mechanical behaviors and failure mechanisms of segmental joints under longitudinal differential settlement were investigated in this study. The validity of the numerical simulation methods was verified through 1:10 scale physical model tests. Subsequently, a full-scale segmental joint model of the Hong Kong-Zhuhai-Macao Bridge (HZMB) immersed tunnel was established. Systematic analyses of the mechanical responses, damage evolution, and sensitive damage zones were conducted. Based on the observations, an optimized design scheme was proposed. It provides theoretical and technical support for structural health monitoring and optimization. The results indicate that the bending resistance of semi-rigid element segment joints is provided primarily by the prestressed cables on the open side. As the rotation angle increases, the rotation center moves upward, and the contact stress concentrates on the top plate. The shear force of the shear keys first decreases and then increases. This is related to their mechanical performance. Shear keys function mainly in shear rather than bending. Tensile and compressive damage concentration zones oriented at 45° form near the shear keys in both middle-wall and side-walls of the segments. The tensile damage at the side-wall shear keys occurs earlier. At 0.004 rad, tensile damage is observed at the middle-wall shear keys (also oriented at 45°). Based on the damage characteristics of the segmental joint, an optimized design scheme using high ductility concrete (HDC) for vertical shear keys was proposed. After optimization, the toughness of the shear keys was enhanced significantly, and the plastic damage was delayed effectively.
{"title":"Mechanical performance and damage characteristics of segmental joints in semi-rigid element immersed tunnel under bending deformation: A combined experimental and numerical study","authors":"Zhinan Hu , Yuejian Wang , Shaobo Qin , Shunde Yin , Haiyang Pan , Kaimeng Ma","doi":"10.1016/j.tust.2025.107427","DOIUrl":"10.1016/j.tust.2025.107427","url":null,"abstract":"<div><div>The mechanical performance of segmental joints in semi-rigid element immersed tunnels is influenced significantly by differential settlement. The mechanical behaviors and failure mechanisms of segmental joints under longitudinal differential settlement were investigated in this study. The validity of the numerical simulation methods was verified through 1:10 scale physical model tests. Subsequently, a full-scale segmental joint model of the Hong Kong-Zhuhai-Macao Bridge (HZMB) immersed tunnel was established. Systematic analyses of the mechanical responses, damage evolution, and sensitive damage zones were conducted. Based on the observations, an optimized design scheme was proposed. It provides theoretical and technical support for structural health monitoring and optimization. The results indicate that the bending resistance of semi-rigid element segment joints is provided primarily by the prestressed cables on the open side. As the rotation angle increases, the rotation center moves upward, and the contact stress concentrates on the top plate. The shear force of the shear keys first decreases and then increases. This is related to their mechanical performance. Shear keys function mainly in shear rather than bending. Tensile and compressive damage concentration zones oriented at 45° form near the shear keys in both middle-wall and side-walls of the segments. The tensile damage at the side-wall shear keys occurs earlier. At 0.004 rad, tensile damage is observed at the middle-wall shear keys (also oriented at 45°). Based on the damage characteristics of the segmental joint, an optimized design scheme using high ductility concrete (HDC) for vertical shear keys was proposed. After optimization, the toughness of the shear keys was enhanced significantly, and the plastic damage was delayed effectively.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107427"},"PeriodicalIF":7.4,"publicationDate":"2026-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145895543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.tust.2025.107439
Xiaojiang Liu , Zhao-Dong Xu , Jun Dai , Jiayu Che , Zhong-Wei Hu , Defu Che
A series of full-scale fire experiments were conducted in the largest utility tunnel platform in China (100 m × 3 m × 3 m), aiming to investigate the flame behavior and thermal flow evolution of utility tunnel fires. Both oil pool fires and cable fires were employed to realistically replicate fire scenes while maintaining reasonable costs. The heat release rates, ventilation conditions, multiple fire sources, and cable arrangements were analyzed comprehensively. Oil pool fires were conducted to simulate the thermal output of early-stage cable fires, results under ventilated conditions demonstrated downstream shifts in peak temperatures and asymmetric longitudinal temperature distributions due to interactions between hot smoke and opposing airflow. In cable fires, heat release accumulates through layer-by-layer ignition pattern. The flame initially propagates vertically, then transitions to longitudinal spread after sufficient thermal accumulation. Based on these findings, shutting down ventilation and sealing openings during early fire stages is recommended to limit oxygen supply, as analyzed from ventilation tests under both oil pool and cable fire cases. Optimizing cable layout can further mitigate vertical flame spread, such as placing cables in lower bracket layers and adding fire-resistant partitions, based on the results from cable fire tests. These results provide primary full-scale experimental data and new insights into the distinct fire dynamics and thermal behavior of spreading fire sources in elongated, confined utility tunnels, offering valuable references for fire safety design and risk control in similar infrastructures.
在国内最大的公用隧道平台（100 m × 3 m × 3 m）上进行了一系列全尺寸火灾实验，研究了公用隧道火灾的火焰行为和热流演变。油田火灾和电缆火灾都可以在保持合理成本的情况下真实地复制火灾场景。对放热速率、通风条件、多火源、电缆布置等进行了综合分析。采用油池火灾模拟了早期电缆火灾的热输出，通风条件下的结果表明，由于热烟和反向气流之间的相互作用，峰值温度向下移动，纵向温度分布不对称。在电缆火灾中，热量释放是通过一层一层的点火模式积累起来的。火焰最初垂直传播，然后在足够的热积累后转变为纵向传播。根据这些发现，根据油池和电缆火灾情况下的通风测试分析，建议在火灾早期关闭通风并密封开口，以限制氧气供应。根据电缆火灾测试结果，优化电缆布局可以进一步减少垂直火焰蔓延，例如将电缆放置在较低的支架层并增加防火隔板。这些结果提供了第一手的全尺寸实验数据，并对细长密闭公用设施隧道中蔓延火源的独特火灾动力学和热行为有了新的认识，为类似基础设施的消防安全设计和风险控制提供了有价值的参考。
{"title":"Full-scale experimental study of flame behavior and thermal distribution in utility tunnel fires","authors":"Xiaojiang Liu , Zhao-Dong Xu , Jun Dai , Jiayu Che , Zhong-Wei Hu , Defu Che","doi":"10.1016/j.tust.2025.107439","DOIUrl":"10.1016/j.tust.2025.107439","url":null,"abstract":"<div><div>A series of full-scale fire experiments were conducted in the largest utility tunnel platform in China (100 m × 3 m × 3 m), aiming to investigate the flame behavior and thermal flow evolution of utility tunnel fires. Both oil pool fires and cable fires were employed to realistically replicate fire scenes while maintaining reasonable costs. The heat release rates, ventilation conditions, multiple fire sources, and cable arrangements were analyzed comprehensively. Oil pool fires were conducted to simulate the thermal output of early-stage cable fires, results under ventilated conditions demonstrated downstream shifts in peak temperatures and asymmetric longitudinal temperature distributions due to interactions between hot smoke and opposing airflow. In cable fires, heat release accumulates through layer-by-layer ignition pattern. The flame initially propagates vertically, then transitions to longitudinal spread after sufficient thermal accumulation. Based on these findings, shutting down ventilation and sealing openings during early fire stages is recommended to limit oxygen supply, as analyzed from ventilation tests under both oil pool and cable fire cases. Optimizing cable layout can further mitigate vertical flame spread, such as placing cables in lower bracket layers and adding fire-resistant partitions, based on the results from cable fire tests. These results provide primary full-scale experimental data and new insights into the distinct fire dynamics and thermal behavior of spreading fire sources in elongated, confined utility tunnels, offering valuable references for fire safety design and risk control in similar infrastructures.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107439"},"PeriodicalIF":7.4,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.tust.2025.107410
Guangzhe Tao , Zongqing Zhou , Bing Shao , Ning Liu , Chenglu Gao , Daosheng Zhang
The fault is one of the key factors that restricts the stability of surrounding rock masses in underground caverns. A comprehensive method including theoretical analysis, numerical simulation, and field investigation was conducted to investigate the failure mechanisms and control strategy of fault based on the underground cavern of the Kala (KL) hydropower station in Southwest China. Firstly, a mechanical failure criterion of fault failure was derived based on Anderson’s fault stress model and the Mohr-Coulomb criterion. Then, discrete element numerical software 3DEC was used to reveal the evolution process of fault slip and the influence mechanisms of system parameters, including shear stiffness, fault dip angle, and shear strength. Finally, a support and control strategy for fault stability was proposed based on the fault instability failure mechanism, which was implemented in the field. The results indicate that fault stability increases with increasing internal friction angle, cohesion, and minimum principal stress, but decreases with increasing maximum principal stress. The fault slip process exhibits three distinct successive stages: slow growth, rapid evolution, and stable equilibrium. Numerical results show that fault slip displacement follows a nonlinear trend with increasing dip angle (increasing first and then decreasing) and decreases significantly with higher shear stiffness and internal friction angle. A synergistic support strategy including “precision blasting + timely support” and “shotcrete + prestressed rockbolt + prestressed cables” was proposed based on the fault failure mechanism, which significantly reduces the risk of fault instability activation. Field monitoring indicates that the support scheme significantly reduces the tendency for fault instability, enhancing the stability of the surrounding rock.
{"title":"Failure mechanism and stability control of fault induced by underground cavern excavation: insights from theoretical analysis and numerical modeling","authors":"Guangzhe Tao , Zongqing Zhou , Bing Shao , Ning Liu , Chenglu Gao , Daosheng Zhang","doi":"10.1016/j.tust.2025.107410","DOIUrl":"10.1016/j.tust.2025.107410","url":null,"abstract":"<div><div>The fault is one of the key factors that restricts the stability of surrounding rock masses in underground caverns. A comprehensive method including theoretical analysis, numerical simulation, and field investigation was conducted to investigate the failure mechanisms and control strategy of fault based on the underground cavern of the Kala (KL) hydropower station in Southwest China. Firstly, a mechanical failure criterion of fault failure was derived based on Anderson’s fault stress model and the Mohr-Coulomb criterion. Then, discrete element numerical software 3DEC was used to reveal the evolution process of fault slip and the influence mechanisms of system parameters, including shear stiffness, fault dip angle, and shear strength. Finally, a support and control strategy for fault stability was proposed based on the fault instability failure mechanism, which was implemented in the field. The results indicate that fault stability increases with increasing internal friction angle, cohesion, and minimum principal stress, but decreases with increasing maximum principal stress. The fault slip process exhibits three distinct successive stages: slow growth, rapid evolution, and stable equilibrium. Numerical results show that fault slip displacement follows a nonlinear trend with increasing dip angle (increasing first and then decreasing) and decreases significantly with higher shear stiffness and internal friction angle. A synergistic support strategy including “precision blasting + timely support” and “shotcrete + prestressed rockbolt + prestressed cables” was proposed based on the fault failure mechanism, which significantly reduces the risk of fault instability activation. Field monitoring indicates that the support scheme significantly reduces the tendency for fault instability, enhancing the stability of the surrounding rock.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"170 ","pages":"Article 107410"},"PeriodicalIF":7.4,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145883911","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-02DOI: 10.1016/j.tust.2025.107417
Yao Zhang , Ruanxiang Xiong , Panpan Cheng , Yibo Chen , Weigang Zhao , Kaihang Han , Xi Jiang , Hehua Zhu , Zhiguo Yan
The limitations of conventional reinforced concrete (RC) lining segments in complex geological and fire-prone environments have driven the demand for more durable and fire-resilient materials in shield tunnel construction. Ultra-high-performance concrete (UHPC) offers outstanding strength and durability but is vulnerable to explosive spalling and rapid strength degradation at elevated temperatures. This study develops a multi-scale fiber-reinforced ultra-high-performance concrete (MSFUHPC) incorporating steel, polyethylene, and carbon fibers, together with fly ash cenospheres (CE), aiming to enhance thermal stability, suppress spalling, and reduce thermal degradation through their synergistic effects. Comparative experiments investigate the spalling behavior and mechanical performance of MSFUHPC segments with and without rebars, under both ambient conditions and hydrocarbon (HC) fire conditions. Results show that MSFUHPC segments exhibit superior fire resistance, reduced spalling depth, and improved load-bearing capacity compared with conventional concrete. CE-containing segments exhibit a maximum spalling depth of only around 5 mm and retain up to 2.9 times the post-fire load-bearing capacity of RC linings. Rebars further mitigate spalling and enhance post-fire ductility by improving heat dissipation and stress redistribution, and their partial strength recovery after cooling contributes to residual capacity retention. Overall, MSFUHPC demonstrates excellent mechanical stability, spalling resistance, and post-fire recovery, offering a practical and fire-resilient material solution for next-generation shield tunnel linings.
{"title":"Experimental investigation on the fire performance of novel multi-scale fiber reinforced UHPC segments","authors":"Yao Zhang , Ruanxiang Xiong , Panpan Cheng , Yibo Chen , Weigang Zhao , Kaihang Han , Xi Jiang , Hehua Zhu , Zhiguo Yan","doi":"10.1016/j.tust.2025.107417","DOIUrl":"10.1016/j.tust.2025.107417","url":null,"abstract":"<div><div>The limitations of conventional reinforced concrete (RC) lining segments in complex geological and fire-prone environments have driven the demand for more durable and fire-resilient materials in shield tunnel construction. Ultra-high-performance concrete (UHPC) offers outstanding strength and durability but is vulnerable to explosive spalling and rapid strength degradation at elevated temperatures. This study develops a multi-scale fiber-reinforced ultra-high-performance concrete (MSFUHPC) incorporating steel, polyethylene, and carbon fibers, together with fly ash cenospheres (CE), aiming to enhance thermal stability, suppress spalling, and reduce thermal degradation through their synergistic effects. Comparative experiments investigate the spalling behavior and mechanical performance of MSFUHPC segments with and without rebars, under both ambient conditions and hydrocarbon (HC) fire conditions. Results show that MSFUHPC segments exhibit superior fire resistance, reduced spalling depth, and improved load-bearing capacity compared with conventional concrete. CE-containing segments exhibit a maximum spalling depth of only around 5 mm and retain up to 2.9 times the post-fire load-bearing capacity of RC linings. Rebars further mitigate spalling and enhance post-fire ductility by improving heat dissipation and stress redistribution, and their partial strength recovery after cooling contributes to residual capacity retention. Overall, MSFUHPC demonstrates excellent mechanical stability, spalling resistance, and post-fire recovery, offering a practical and fire-resilient material solution for next-generation shield tunnel linings.</div></div>","PeriodicalId":49414,"journal":{"name":"Tunnelling and Underground Space Technology","volume":"171 ","pages":"Article 107417"},"PeriodicalIF":7.4,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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