Pub Date : 2026-04-01Epub Date: 2026-01-05DOI: 10.1016/j.undsp.2025.10.004
Oveis Farzay, Marilena Cardu
Accurate TBM performance estimation is essential for effective tunnel design and planning. This study introduces a one-dimensional (1D) estimation model that estimates thrust, torque, power, cutterhead speed, and tool count using only excavation diameter. The model was developed across four TBM types—open, single shield (SS), double shield (DS), and earth pressure balance (EPB)—to isolate the influence of diameter from other variables. Validation against existing models and a 52-case independent dataset confirmed strong correlations: torque scales with the cube of the excavation diameter (R2 = 0.89 for EPB), power grows faster than linearly (R2 = 0.83 for EPB), thrust increases supra-linearly (R2 = 0.79 for EPB), and cutterhead speed decreases with diameter (R2 = 0.87 for open TBM). Tool count grows proportionally. A reliability matrix compares model accuracy and data support, aiding selection based on both fitness and robustness. This 1D model offers fast, consistent estimates for early-stage assessments. While it excludes detailed geological input, it is suited for feasibility studies and preliminary design. Future work will incorporate additional ground and machine parameters and extend validation across a broader range of tunneling conditions to enhance generalizability.
{"title":"Reliability analysis of 1D estimation for TBM operational parameters","authors":"Oveis Farzay, Marilena Cardu","doi":"10.1016/j.undsp.2025.10.004","DOIUrl":"10.1016/j.undsp.2025.10.004","url":null,"abstract":"<div><div>Accurate TBM performance estimation is essential for effective tunnel design and planning. This study introduces a one-dimensional (1D) estimation model that estimates thrust, torque, power, cutterhead speed, and tool count using only excavation diameter. The model was developed across four TBM types—open, single shield (SS), double shield (DS), and earth pressure balance (EPB)—to isolate the influence of diameter from other variables. Validation against existing models and a 52-case independent dataset confirmed strong correlations: torque scales with the cube of the excavation diameter (<em>R</em><sup>2</sup> = 0.89 for EPB), power grows faster than linearly (<em>R</em><sup>2</sup> = 0.83 for EPB), thrust increases supra-linearly (<em>R</em><sup>2</sup> = 0.79 for EPB), and cutterhead speed decreases with diameter (<em>R</em><sup>2</sup> = 0.87 for open TBM). Tool count grows proportionally. A reliability matrix compares model accuracy and data support, aiding selection based on both fitness and robustness. This 1D model offers fast, consistent estimates for early-stage assessments. While it excludes detailed geological input, it is suited for feasibility studies and preliminary design. Future work will incorporate additional ground and machine parameters and extend validation across a broader range of tunneling conditions to enhance generalizability.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"27 ","pages":"Pages 72-91"},"PeriodicalIF":8.3,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080871","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 : 2026-04-01Epub Date: 2026-01-05DOI: 10.1016/j.undsp.2025.10.003
Ruikun Wang , Gang Zheng , Huayang Lei , Xuesong Cheng , Eng-Choon Leong , Yetao Ji
This study investigated the long-term settlement behaviour of piled buildings induced by shield tunnelling in soft ground conditions within urban environments. By integrating a detailed case study with advanced numerical modelling techniques, this study provided a nuanced understanding of the interactions between tunnel construction and existing pile foundations. Central to the investigation is the role of soil consolidation, which significantly contributes to the settlement of piled buildings. To address this, this study emphasizes the critical need for the precise calibration of tunnelling parameters such as face pressure and grouting pressures. These parameters are meticulously controlled to mitigate the adverse effects on nearby piled buildings, ensuring their stability and integrity. It is established that an optimal face pressure, set at 90% of the lateral earth pressure, consistently minimizes the settlement of piled buildings, primarily due to the minimal reduction in the pile toe resistance observed near the tunnel. Similarly, the ideal grouting pressure was identified to be within the range of 120%–160% of the vertical earth pressure, with the smallest building settlement and decrease in pile toe resistance observed at a grouting pressure of 150% of the overburden pressure. This finding elucidates the load transfer mechanism within piled buildings. This study further demonstrated that the settlement induced by the second tunnel excavation is smaller than that caused by the first tunnel excavation owing to the sheltering effects of the adjacent first tunnel and pile foundations. During the consolidation phase following tunnel excavation, the settlement caused by the second tunnel is smaller than that caused by the first tunnel, which is attributed to the dissipation of the negative excess pore pressure around the first tunnel, leading to soil volume expansion. These insights not only validate the effectiveness of the numerical model but also contribute significantly to the field of geotechnical engineering by providing actionable guidelines for future tunnelling projects.
{"title":"Effects of shield tunnelling parameters on the long-term settlement of piled buildings in soft ground","authors":"Ruikun Wang , Gang Zheng , Huayang Lei , Xuesong Cheng , Eng-Choon Leong , Yetao Ji","doi":"10.1016/j.undsp.2025.10.003","DOIUrl":"10.1016/j.undsp.2025.10.003","url":null,"abstract":"<div><div>This study investigated the long-term settlement behaviour of piled buildings induced by shield tunnelling in soft ground conditions within urban environments. By integrating a detailed case study with advanced numerical modelling techniques, this study provided a nuanced understanding of the interactions between tunnel construction and existing pile foundations. Central to the investigation is the role of soil consolidation, which significantly contributes to the settlement of piled buildings. To address this, this study emphasizes the critical need for the precise calibration of tunnelling parameters such as face pressure and grouting pressures. These parameters are meticulously controlled to mitigate the adverse effects on nearby piled buildings, ensuring their stability and integrity. It is established that an optimal face pressure, set at 90% of the lateral earth pressure, consistently minimizes the settlement of piled buildings, primarily due to the minimal reduction in the pile toe resistance observed near the tunnel. Similarly, the ideal grouting pressure was identified to be within the range of 120%–160% of the vertical earth pressure, with the smallest building settlement and decrease in pile toe resistance observed at a grouting pressure of 150% of the overburden pressure. This finding elucidates the load transfer mechanism within piled buildings. This study further demonstrated that the settlement induced by the second tunnel excavation is smaller than that caused by the first tunnel excavation owing to the sheltering effects of the adjacent first tunnel and pile foundations. During the consolidation phase following tunnel excavation, the settlement caused by the second tunnel is smaller than that caused by the first tunnel, which is attributed to the dissipation of the negative excess pore pressure around the first tunnel, leading to soil volume expansion. These insights not only validate the effectiveness of the numerical model but also contribute significantly to the field of geotechnical engineering by providing actionable guidelines for future tunnelling projects.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"27 ","pages":"Pages 24-44"},"PeriodicalIF":8.3,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080774","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 : 2026-04-01Epub Date: 2026-01-07DOI: 10.1016/j.undsp.2025.10.006
Tianqi Zhang, Bangguo He, Zhitong Chen, Gang Zheng, Chang Liu
Leakage disasters in shield tunnels frequently occur, leading to severe consequences such as tunnel collapse, road collapse, and building destruction. Since it is difficult to record the accident evolution process onsite, it is necessary to reproduce it through credible numerical simulations. However, traditional numerical methods face technical bottlenecks when simulating water–sand inrush in shield tunnels due to challenges such as large deformation analysis and fluid–structure coupling, making it difficult to simulate the process of disaster progression. To address this issue, a Coupled Eulerian–Lagrangian (CEL) method incorporating seepage analysis, referred to as the S-CEL method, was proposed to simulate the interaction between water, soil, and a shield tunnel during a disaster. A refined three-dimensional numerical model was developed using the S-CEL method to simulate the water–sand inrush process. The generation sequence of new leakage points at the segment joints and the mechanisms driving the progression of the disaster were revealed. New leakage points were progressively generated along the longitudinal direction of the tunnel. As the number of leakage rings increased, the amount of soil loss increased rapidly. This led to severe uneven settlement and dislocation deformation of the tunnel. A channel steel was introduced to reinforce the tunnel in the numerical simulation to mitigate or decelerate the progression of the leakage disaster. The connection method between the channel steel and tunnel segments was found to be pivotal to the strengthening effect. Employing only bolt anchoring showed limited efficacy, while enhancing the segment-steel interface with epoxy resin achieved much better performance in mitigating disaster progression.
{"title":"Numerical simulation on progressive leakage in shield tunnel and corresponding mitigation","authors":"Tianqi Zhang, Bangguo He, Zhitong Chen, Gang Zheng, Chang Liu","doi":"10.1016/j.undsp.2025.10.006","DOIUrl":"10.1016/j.undsp.2025.10.006","url":null,"abstract":"<div><div>Leakage disasters in shield tunnels frequently occur, leading to severe consequences such as tunnel collapse, road collapse, and building destruction. Since it is difficult to record the accident evolution process onsite, it is necessary to reproduce it through credible numerical simulations. However, traditional numerical methods face technical bottlenecks when simulating water–sand inrush in shield tunnels due to challenges such as large deformation analysis and fluid–structure coupling, making it difficult to simulate the process of disaster progression. To address this issue, a Coupled Eulerian–Lagrangian (CEL) method incorporating seepage analysis, referred to as the S-CEL method, was proposed to simulate the interaction between water, soil, and a shield tunnel during a disaster. A refined three-dimensional numerical model was developed using the S-CEL method to simulate the water–sand inrush process. The generation sequence of new leakage points at the segment joints and the mechanisms driving the progression of the disaster were revealed. New leakage points were progressively generated along the longitudinal direction of the tunnel. As the number of leakage rings increased, the amount of soil loss increased rapidly. This led to severe uneven settlement and dislocation deformation of the tunnel. A channel steel was introduced to reinforce the tunnel in the numerical simulation to mitigate or decelerate the progression of the leakage disaster. The connection method between the channel steel and tunnel segments was found to be pivotal to the strengthening effect. Employing only bolt anchoring showed limited efficacy, while enhancing the segment-steel interface with epoxy resin achieved much better performance in mitigating disaster progression.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"27 ","pages":"Pages 45-57"},"PeriodicalIF":8.3,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080870","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 : 2026-04-01Epub Date: 2026-01-08DOI: 10.1016/j.undsp.2025.10.007
Qing Ma , Wei Zhang , Xiaoli Liu , Weiqiang Xie , Ruosong Wang , Jinpeng Zhao
The development of large cross-section tunnels is an inevitable trend driven by the intensification of coal mining activities and advancements in mining equipment technology. However, the disturbance stress exerted by adjacent caverns has a more pronounced impact on weakly cemented rock strata in the vicinity of neighboring tunnels. To mitigate deformation in weakly cemented tunnels, grouting and the installation of long anchor cables were employed to reinforce the self-supporting capacity of the surrounding rock, thereby establishing an active support layer. Additionally, U-shaped steel frames combined with the subsequent application of flexible filling materials were utilized to aid the surrounding rock in mobilizing its self-supporting capacity, which resulted in the formation of a passive support layer. A layered collaborative control methodology integrating both active and passive support mechanisms was developed and implemented in engineering practice. The findings demonstrate that the vertical stress was alleviated after cavern excavation and was predominantly transferred toward the adjacent tunnel, with the influence zone extending approximately 7 to 12 times the tunnel height. Conversely, the horizontal stress is primarily dispersed laterally, affecting a region approximately 3 to 6 times the tunnel width. Following the infilling of pebbles between the U-shaped steel frame and the adjacent rock mass, the maximum compressive stress experienced by the U-shaped steel frame decreased by 50%. Additionally, the spatial extent of the maximum axial force was reduced by 65%, whereas the stresses within the rock bolts and cable bolts increased by 30% and 40%, respectively. Grouting reinforcement contributed to bonding and compaction effects on the delamination and fracturing of the roof strata, with the grout predominantly distributed within a range of 1.5 to 5 m from the central region of the roof. The research outcomes presented in this paper can provide valuable reference for a large-section weakly cemented tunnel.
{"title":"Combined active and passive support technology and its application for deformation control in large-section weakly cemented tunnel","authors":"Qing Ma , Wei Zhang , Xiaoli Liu , Weiqiang Xie , Ruosong Wang , Jinpeng Zhao","doi":"10.1016/j.undsp.2025.10.007","DOIUrl":"10.1016/j.undsp.2025.10.007","url":null,"abstract":"<div><div>The development of large cross-section tunnels is an inevitable trend driven by the intensification of coal mining activities and advancements in mining equipment technology. However, the disturbance stress exerted by adjacent caverns has a more pronounced impact on weakly cemented rock strata in the vicinity of neighboring tunnels. To mitigate deformation in weakly cemented tunnels, grouting and the installation of long anchor cables were employed to reinforce the self-supporting capacity of the surrounding rock, thereby establishing an active support layer. Additionally, U-shaped steel frames combined with the subsequent application of flexible filling materials were utilized to aid the surrounding rock in mobilizing its self-supporting capacity, which resulted in the formation of a passive support layer. A layered collaborative control methodology integrating both active and passive support mechanisms was developed and implemented in engineering practice. The findings demonstrate that the vertical stress was alleviated after cavern excavation and was predominantly transferred toward the adjacent tunnel, with the influence zone extending approximately 7 to 12 times the tunnel height. Conversely, the horizontal stress is primarily dispersed laterally, affecting a region approximately 3 to 6 times the tunnel width. Following the infilling of pebbles between the U-shaped steel frame and the adjacent rock mass, the maximum compressive stress experienced by the U-shaped steel frame decreased by 50%. Additionally, the spatial extent of the maximum axial force was reduced by 65%, whereas the stresses within the rock bolts and cable bolts increased by 30% and 40%, respectively. Grouting reinforcement contributed to bonding and compaction effects on the delamination and fracturing of the roof strata, with the grout predominantly distributed within a range of 1.5 to 5 m from the central region of the roof. The research outcomes presented in this paper can provide valuable reference for a large-section weakly cemented tunnel.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"27 ","pages":"Pages 1-23"},"PeriodicalIF":8.3,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146015807","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}
Despite the thriving development of metro-led urban underground public space (UUPS) and its significant benefits and costs, there remains a critical research gap in understanding and evaluating its efficiency. This paper intends to improve the post-evaluation system of metro-led UUPS by proposing an efficiency evaluation framework based on data envelopment analysis. The public and the private sectors are taken as different coexisting decision-makers, and a pair of linear programming is built accordingly (with different assignments of discretionary and non-discretionary inputs) for each decision-making unit. The directional vector is calculated based on CRITIC weights to model the searching process of referential cases in terms of urban renewal. The empirical study of twenty metro-led UUPSs in central Shanghai reveals that (1) the proposed evaluation framework is feasible and discriminative, (2) the efficient form of metro-led UUPS in Shanghai is mainly limited to a compact pattern with a low proportion of pure public space, (3) the essential solution to promote efficiencies is closer cooperation between different parties, and (4) efficiency evaluation is crucial to avoiding the “the-more-the-better” type of development. The findings of this study are expected to shed light on the future planning and operation of metro-led UUPS.
{"title":"A DEA–based efficiency evaluation method for metro-led urban underground public space","authors":"Zi-Yun Zhang, Fang-Le Peng, Chen-Xiao Ma, Yong-Kang Qiao","doi":"10.1016/j.undsp.2025.02.013","DOIUrl":"10.1016/j.undsp.2025.02.013","url":null,"abstract":"<div><div>Despite the thriving development of metro-led urban underground public space (UUPS) and its significant benefits and costs, there remains a critical research gap in understanding and evaluating its efficiency. This paper intends to improve the post-evaluation system of metro-led UUPS by proposing an efficiency evaluation framework based on data envelopment analysis. The public and the private sectors are taken as different coexisting decision-makers, and a pair of linear programming is built accordingly (with different assignments of discretionary and non-discretionary inputs) for each decision-making unit. The directional vector is calculated based on CRITIC weights to model the searching process of referential cases in terms of urban renewal. The empirical study of twenty metro-led UUPSs in central Shanghai reveals that (1) the proposed evaluation framework is feasible and discriminative, (2) the efficient form of metro-led UUPS in Shanghai is mainly limited to a compact pattern with a low proportion of pure public space, (3) the essential solution to promote efficiencies is closer cooperation between different parties, and (4) efficiency evaluation is crucial to avoiding the “the-more-the-better” type of development. The findings of this study are expected to shed light on the future planning and operation of metro-led UUPS.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"27 ","pages":"Pages 58-71"},"PeriodicalIF":8.3,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146080872","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 : 2026-02-01Epub Date: 2025-12-24DOI: 10.1016/j.undsp.2025.10.001
Hao Liu , Zenghui Zhao , Qing Ma , Xiaoli Liu , Longjie Zhu
Driven by the “dual carbon” strategy, the functionality of coal mine underground reservoirs is transitioning toward multimedia collaborative storage, such as CO2 geological sequestration and strategic energy reserves. The microscopic structures of the coal pillar dams, which are subjected to mining-induced damage and long-term infiltration erosion by highly mineralized mine water, continuously deteriorate over time, posing significant risks to the long-term safety and stability of the reservoirs. This study, based on the Lingxin Coal Mine Underground Reservoir Demonstration Project, employs a multi-technique characterization approach including X-ray diffraction (XRD), scanning electron microscope, nuclear magnetic resonance, and computed tomography to systematically reveal the multiscale collaborative erosion mechanisms of highly mineralized mine water on the mineral composition, crystal structure, and pore development of coal pillar dams. The results indicate: (1) significant concentration-dependent deterioration of mineral composition and crystal structure; kaolinite hydrolysis had a weakening effect on XRD peaks while quartz remained inert; (2) initiation of progressive microstructural damage at boundaries via dissolution/loosening; this damage advanced through layered mineral delamination and pore development (evidenced by NMR T2 broadening), resulting in irreversible void formation with chloride precipitation; (3) formation of pore-throat halite crystals, primarily due to chloride ions (Cl–); these crystals propagated microfractures through salt-expansion stress, establishing a cyclic dissolution–migration–crystallization–cracking process; (4) triggering of accelerated deterioration of the coal matrix owing to prolonged retention; this induced time- and concentration-dependent expansion and interconnection of pore-fracture networks, resulting in geomechanical deterioration.
{"title":"Degradation mechanism of microstructure of residual coal pillars during highly mineralized mine-water storage in coal mine goaf","authors":"Hao Liu , Zenghui Zhao , Qing Ma , Xiaoli Liu , Longjie Zhu","doi":"10.1016/j.undsp.2025.10.001","DOIUrl":"10.1016/j.undsp.2025.10.001","url":null,"abstract":"<div><div>Driven by the “dual carbon” strategy, the functionality of coal mine underground reservoirs is transitioning toward multimedia collaborative storage, such as CO<sub>2</sub> geological sequestration and strategic energy reserves. The microscopic structures of the coal pillar dams, which are subjected to mining-induced damage and long-term infiltration erosion by highly mineralized mine water, continuously deteriorate over time, posing significant risks to the long-term safety and stability of the reservoirs. This study, based on the Lingxin Coal Mine Underground Reservoir Demonstration Project, employs a multi-technique characterization approach including X-ray diffraction (XRD), scanning electron microscope, nuclear magnetic resonance, and computed tomography to systematically reveal the multiscale collaborative erosion mechanisms of highly mineralized mine water on the mineral composition, crystal structure, and pore development of coal pillar dams. The results indicate: (1) significant concentration-dependent deterioration of mineral composition and crystal structure; kaolinite hydrolysis had a weakening effect on XRD peaks while quartz remained inert; (2) initiation of progressive microstructural damage at boundaries via dissolution/loosening; this damage advanced through layered mineral delamination and pore development (evidenced by NMR <em>T</em><sub>2</sub> broadening), resulting in irreversible void formation with chloride precipitation; (3) formation of pore-throat halite crystals, primarily due to chloride ions (Cl<sup>–</sup>); these crystals propagated microfractures through salt-expansion stress, establishing a cyclic dissolution–migration–crystallization–cracking process; (4) triggering of accelerated deterioration of the coal matrix owing to prolonged retention; this induced time- and concentration-dependent expansion and interconnection of pore-fracture networks, resulting in geomechanical deterioration.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"26 ","pages":"Pages 479-497"},"PeriodicalIF":8.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145925067","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 : 2026-02-01Epub Date: 2025-12-04DOI: 10.1016/j.undsp.2025.09.004
Yajuan Li, Xueying Bao
Tunnels are critical transportation infrastructure, with >80% of their lifecycle carbon emissions from the design phase. Therefore, low-carbon design is a pathway to achieving “zero carbon” goals. However, multi-source and heterogeneous design information creates challenges because of tunnel carbon emission data silos. This study proposes a carbon emissions-structure-design framework with a multi-layered integrated structure for tunnel carbon footprint assessment, clarifying the relationships among design parameters, structural characteristics, and carbon emissions. Additionally, a design structure matrix-carbon footprint model is established to analyze the relationships between low-carbon design elements (LDEs) and the lifecycle carbon footprint. A model is developed to examine the nonlinear mechanisms by which LDEs affect carbon emissions. Case studies indicate that carbon emissions during the construction phase primarily arise from tunnel boring machine excavation, slag transportation, shotcreting, and tunnel lining. They are significantly influenced by LDEs, such as the surrounding rock grade, tunnel radius, advance rate, and slope, which exhibit threshold effects. In the operational phase, carbon emissions are dominated by train traction energy consumption, which increases with speed and decreases with radius. This is in contrast to the construction phase, where larger radii lead to higher emissions. This study integrates tunnel design parameters with lifecycle carbon emissions to overcome the limitations of traditional segmented approaches. The findings provide a decision-support framework for source-level emission reduction during the design phase, enabling engineers to predict carbon emissions for parameter combinations and offer a new strategy for achieving carbon neutrality in transportation infrastructure.
{"title":"Carbon emission mechanism and influence of design-oriented railway tunnel engineering","authors":"Yajuan Li, Xueying Bao","doi":"10.1016/j.undsp.2025.09.004","DOIUrl":"10.1016/j.undsp.2025.09.004","url":null,"abstract":"<div><div>Tunnels are critical transportation infrastructure, with >80% of their lifecycle carbon emissions from the design phase. Therefore, low-carbon design is a pathway to achieving “zero carbon” goals. However, multi-source and heterogeneous design information creates challenges because of tunnel carbon emission data silos. This study proposes a carbon emissions-structure-design framework with a multi-layered integrated structure for tunnel carbon footprint assessment, clarifying the relationships among design parameters, structural characteristics, and carbon emissions. Additionally, a design structure matrix-carbon footprint model is established to analyze the relationships between low-carbon design elements (LDEs) and the lifecycle carbon footprint. A model is developed to examine the nonlinear mechanisms by which LDEs affect carbon emissions. Case studies indicate that carbon emissions during the construction phase primarily arise from tunnel boring machine excavation, slag transportation, shotcreting, and tunnel lining. They are significantly influenced by LDEs, such as the surrounding rock grade, tunnel radius, advance rate, and slope, which exhibit threshold effects. In the operational phase, carbon emissions are dominated by train traction energy consumption, which increases with speed and decreases with radius. This is in contrast to the construction phase, where larger radii lead to higher emissions. This study integrates tunnel design parameters with lifecycle carbon emissions to overcome the limitations of traditional segmented approaches. The findings provide a decision-support framework for source-level emission reduction during the design phase, enabling engineers to predict carbon emissions for parameter combinations and offer a new strategy for achieving carbon neutrality in transportation infrastructure.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"26 ","pages":"Pages 435-457"},"PeriodicalIF":8.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839866","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 : 2026-02-01Epub Date: 2025-11-07DOI: 10.1016/j.undsp.2025.07.003
Kai-Fang Yang , Min-Liang Chi , Chang-Jie Xu , Chao-Feng Zeng , Lu-Jv Liang , Zhi Ding , Ya-Shi Qiu
To investigate surface settlement under the combined effect of foundation pit dewatering and excavation, a series of experiments was conducted using a scaled model of a deep foundation pit at a metro station. During experimental simulations of the dry excavation and dewatering processes, data were collected on surface settlement, water heads outside the pit, and deflection of the diaphragm wall. The characteristics of surface settlement were compared and analyzed under different conditions with a focus on the development of surface settlement during dewatering and excavation at key locations outside the pit. The combined effect of dewatering and excavation was found to increase surface settlement outside the pit and expand its area of influence. The insertion ratio of the diaphragm wall (n) significantly affected surface settlement; as the insertion ratio increased, surface settlement, along with its area of influence, decreased. For n < 1.25, the area beyond twice the excavation depth was considered a minor area of settlement influence. In contrast, for n ≥ 1.25, this area wasn’t classified as a minor area of settlement influence. As excavation depth increased, the surface settlement pattern outside the pit transitioned from triangle-type to groove-type, groove-type settlement occurred when As ≥ 1.6Ac, whereas triangle-type settlement occurred under other conditions (As represents the area of the deep inward part of the convex deformation of the diaphragm wall; Ac refers to the cantilever part of the diaphragm wall). This study provides insights into the development of surface settlement during dewatering and excavation and serves as a valuable reference for innovations in sustainable and resilient underground design.
{"title":"Development of surface settlement under the combined effect of foundation pit dewatering and excavation: Insights from experimental modelling","authors":"Kai-Fang Yang , Min-Liang Chi , Chang-Jie Xu , Chao-Feng Zeng , Lu-Jv Liang , Zhi Ding , Ya-Shi Qiu","doi":"10.1016/j.undsp.2025.07.003","DOIUrl":"10.1016/j.undsp.2025.07.003","url":null,"abstract":"<div><div>To investigate surface settlement under the combined effect of foundation pit dewatering and excavation, a series of experiments was conducted using a scaled model of a deep foundation pit at a metro station. During experimental simulations of the dry excavation and dewatering processes, data were collected on surface settlement, water heads outside the pit, and deflection of the diaphragm wall. The characteristics of surface settlement were compared and analyzed under different conditions with a focus on the development of surface settlement during dewatering and excavation at key locations outside the pit. The combined effect of dewatering and excavation was found to increase surface settlement outside the pit and expand its area of influence. The insertion ratio of the diaphragm wall (<em>n</em>) significantly affected surface settlement; as the insertion ratio increased, surface settlement, along with its area of influence, decreased. For <em>n</em> < 1.25, the area beyond twice the excavation depth was considered a minor area of settlement influence. In contrast, for <em>n</em> ≥ 1.25, this area wasn’t classified as a minor area of settlement influence. As excavation depth increased, the surface settlement pattern outside the pit transitioned from triangle-type to groove-type, groove-type settlement occurred when <em>A</em><sub>s</sub> ≥ 1.6<em>A</em><sub>c</sub>, whereas triangle-type settlement occurred under other conditions (<em>A</em><sub>s</sub> represents the area of the deep inward part of the convex deformation of the diaphragm wall; <em>A</em><sub>c</sub> refers to the cantilever part of the diaphragm wall). This study provides insights into the development of surface settlement during dewatering and excavation and serves as a valuable reference for innovations in sustainable and resilient underground design.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"26 ","pages":"Pages 305-320"},"PeriodicalIF":8.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145748052","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}
Automated subsurface utility detection systems in construction rely heavily on the quality of ground-penetrating radar (GPR) profiles, which are often degraded by high-amplitude horizontal interference. Existing low-rank decomposition methods lack the intelligence and flexibility required for multi-site data processing and involve labor-intensive parameter tuning, impeding their integration into intelligent construction workflows. To address these challenges, this paper proposes a horizontal interference suppression algorithm based on a diffusion model, termed GPR-HIDiff. The proposed model replaces conventional sequential convolutional operators with ResBlocks throughout the encoder, intermediate layer, and decoder of the UNet architecture, enhancing training stability. Lightweight agent attention modules are embedded between ResBlocks at each level to improve global information modeling capability. A spatial attention mechanism is deployed between the encoder and decoder to achieve adaptive spatial feature optimization. Furthermore, the forward diffusion phase adopts a cos schedule-based strategy to ensure a smooth temporal variation of noise variance. A standardized dataset comprising real-world measured samples and finite difference time domain simulation samples of urban road models has also been constructed. The effectiveness of the hybrid dataset, the introduced modules, the robustness analysis, and the cos schedule is validated through training with single/mixed datasets, ablation studies, evaluation of metric variations before and after the introduction of different noise levels, and comparative experiments with constant, linear, and cos schedules. Experimental results demonstrate that GPR-HIDiff significantly outperforms both traditional methods and state-of-the-art deep learning models on both simulated and real-world test samples. It effectively suppresses horizontal artifacts, preserves target hyperbolic contours, and avoids excessive reduction of target scattering, showcasing its exceptional performance. This method provides a powerful algorithmic foundation for high-resolution GPR imaging and target detection.
{"title":"GPR-HIDiff: A diffusion-based model for horizontal interference suppression in urban underground detection radar profiles","authors":"Xiaosong Tang , Feng Yang , Xu Qiao , Jialin Liu , Haitao Zuo , Liang Gao , Jianshe Zhao , Suping Peng","doi":"10.1016/j.undsp.2025.08.002","DOIUrl":"10.1016/j.undsp.2025.08.002","url":null,"abstract":"<div><div>Automated subsurface utility detection systems in construction rely heavily on the quality of ground-penetrating radar (GPR) profiles, which are often degraded by high-amplitude horizontal interference. Existing low-rank decomposition methods lack the intelligence and flexibility required for multi-site data processing and involve labor-intensive parameter tuning, impeding their integration into intelligent construction workflows. To address these challenges, this paper proposes a horizontal interference suppression algorithm based on a diffusion model, termed GPR-HIDiff. The proposed model replaces conventional sequential convolutional operators with ResBlocks throughout the encoder, intermediate layer, and decoder of the UNet architecture, enhancing training stability. Lightweight agent attention modules are embedded between ResBlocks at each level to improve global information modeling capability. A spatial attention mechanism is deployed between the encoder and decoder to achieve adaptive spatial feature optimization. Furthermore, the forward diffusion phase adopts a cos<span><math><mi>θ</mi></math></span> schedule-based strategy to ensure a smooth temporal variation of noise variance. A standardized dataset comprising real-world measured samples and finite difference time domain simulation samples of urban road models has also been constructed. The effectiveness of the hybrid dataset, the introduced modules, the robustness analysis, and the cos<span><math><mi>θ</mi></math></span> schedule is validated through training with single<strong>/</strong>mixed datasets, ablation studies, evaluation of metric variations before and after the introduction of different noise levels, and comparative experiments with constant, linear, and cos<span><math><mi>θ</mi></math></span> schedules. Experimental results demonstrate that GPR-HIDiff significantly outperforms both traditional methods and state-of-the-art deep learning models on both simulated and real-world test samples. It effectively suppresses horizontal artifacts, preserves target hyperbolic contours, and avoids excessive reduction of target scattering, showcasing its exceptional performance. This method provides a powerful algorithmic foundation for high-resolution GPR imaging and target detection.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"26 ","pages":"Pages 458-478"},"PeriodicalIF":8.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145839865","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}
Optimizing shield tunnel joints is essential to meet the evolving demands of modern construction, where balancing structural performance, environmental impact, and cost efficiency is increasingly important. Traditional cast iron joint (CIJ) has been widely used, but there remains significant room for improvement in terms of both their mechanical efficiency and sustainability. This study addresses these challenges by investigating two alternative designs: the single row sleeve joint (SRSJ) and the double row sleeve joint (DRSJ). The research focuses on evaluating their mechanical performance and potential to reduce carbon emissions and costs, offering a more comprehensive and future-forward solution compared to the traditional CIJ. Through experimental testing, key performance factors such as joint deflection, rotational angle, concrete strain, and bolt strain were analyzed alongside joint toughness, ductility, cracking patterns, embodied carbon, and material cost. Key findings revealed that SRSJ achieved 97% of CIJ’s ultimate bearing capacity, while DRSJ reached only 75%. In the elastic phase, SRSJ performed significantly better, supporting twice the load of CIJ. Bolt strain analysis showed that DRSJ experienced greater stress concentration, while SRSJ maintained balanced strain distribution. SRSJ also outperformed CIJ and DRSJ in toughness and ductility, particularly in rotational flexibility, exceeding CIJ by 76%. SRSJ and DRSJ all demonstrated lower embodied carbon and costs compared to CIJ, with reductions of up to 7.21% in emissions and 6.42% in costs. Overall, SRSJ emerged as a viable alternative, balancing mechanical performance, sustainability, and cost efficiency. In contrast, DRSJ’s stress concentration issues limited its effectiveness, making it less advantageous compared to CIJ.
{"title":"Optimization of shield tunnel joints: Focusing on structural performance with considerations for low-carbon emissions and economic efficiency","authors":"Minjin Cai , Timon Rabczuk , Shuwei Zhou , Xiaoying Zhuang","doi":"10.1016/j.undsp.2025.02.012","DOIUrl":"10.1016/j.undsp.2025.02.012","url":null,"abstract":"<div><div>Optimizing shield tunnel joints is essential to meet the evolving demands of modern construction, where balancing structural performance, environmental impact, and cost efficiency is increasingly important. Traditional cast iron joint (CIJ) has been widely used, but there remains significant room for improvement in terms of both their mechanical efficiency and sustainability. This study addresses these challenges by investigating two alternative designs: the single row sleeve joint (SRSJ) and the double row sleeve joint (DRSJ). The research focuses on evaluating their mechanical performance and potential to reduce carbon emissions and costs, offering a more comprehensive and future-forward solution compared to the traditional CIJ. Through experimental testing, key performance factors such as joint deflection, rotational angle, concrete strain, and bolt strain were analyzed alongside joint toughness, ductility, cracking patterns, embodied carbon, and material cost. Key findings revealed that SRSJ achieved 97% of CIJ’s ultimate bearing capacity, while DRSJ reached only 75%. In the elastic phase, SRSJ performed significantly better, supporting twice the load of CIJ. Bolt strain analysis showed that DRSJ experienced greater stress concentration, while SRSJ maintained balanced strain distribution. SRSJ also outperformed CIJ and DRSJ in toughness and ductility, particularly in rotational flexibility, exceeding CIJ by 76%. SRSJ and DRSJ all demonstrated lower embodied carbon and costs compared to CIJ, with reductions of up to 7.21% in emissions and 6.42% in costs. Overall, SRSJ emerged as a viable alternative, balancing mechanical performance, sustainability, and cost efficiency. In contrast, DRSJ’s stress concentration issues limited its effectiveness, making it less advantageous compared to CIJ.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"26 ","pages":"Pages 412-434"},"PeriodicalIF":8.3,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145797218","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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