Underground Space最新文献

Wall movement during dewatering inside a diaphragm wall before soil excavation

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-04-03 DOI: 10.1016/j.undsp.2025.01.003

Chao-Feng Zeng , William Powrie , Chang-Jie Xu , Xiu-Li Xue

Significant movement of in-situ retaining walls is usually assumed to begin with bulk excavation. However, an increasing number of case studies show that lowering the pore water pressures inside a diaphragm wall-type basement enclosure prior to bulk excavation can cause wall movements in the order of some centimeters. This paper describes the results of a laboratory-scale experiment carried out to explore mechanisms of in situ retaining wall movement associated with dewatering inside the enclosure prior to bulk excavation. Dewatering reduces the pore water pressures inside the enclosure more than outside, resulting in the wall moving as an unpropped cantilever supported only by the soil. Lateral effective stresses in the shallow soil behind the wall are reduced, while lateral effective stresses in front of the wall increase. Although the associated lateral movement was small in the laboratory experiment, the movement could be proportionately larger in the field with a less stiff soil and a potentially greater dewatered depth. The implementation of a staged dewatering system, coupled with the potential for phased excavation and propping strategies, can effectively mitigate dewatering-induced wall and soil movements. This approach allows for enhanced stiffness of the wall support system, which can be dynamically adjusted based on real-time displacement monitoring data when necessary.

{"title":"Wall movement during dewatering inside a diaphragm wall before soil excavation","authors":"Chao-Feng Zeng , William Powrie , Chang-Jie Xu , Xiu-Li Xue","doi":"10.1016/j.undsp.2025.01.003","DOIUrl":"10.1016/j.undsp.2025.01.003","url":null,"abstract":"<div><div>Significant movement of in-situ retaining walls is usually assumed to begin with bulk excavation. However, an increasing number of case studies show that lowering the pore water pressures inside a diaphragm wall-type basement enclosure prior to bulk excavation can cause wall movements in the order of some centimeters. This paper describes the results of a laboratory-scale experiment carried out to explore mechanisms of in situ retaining wall movement associated with dewatering inside the enclosure prior to bulk excavation. Dewatering reduces the pore water pressures inside the enclosure more than outside, resulting in the wall moving as an unpropped cantilever supported only by the soil. Lateral effective stresses in the shallow soil behind the wall are reduced, while lateral effective stresses in front of the wall increase. Although the associated lateral movement was small in the laboratory experiment, the movement could be proportionately larger in the field with a less stiff soil and a potentially greater dewatered depth. The implementation of a staged dewatering system, coupled with the potential for phased excavation and propping strategies, can effectively mitigate dewatering-induced wall and soil movements. This approach allows for enhanced stiffness of the wall support system, which can be dynamically adjusted based on real-time displacement monitoring data when necessary.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 355-368"},"PeriodicalIF":8.2,"publicationDate":"2025-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143829864","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}

引用次数: 0

Corrosion characteristic of multi-ring shield tunnel containing rubber concrete invert-filling under direct stray current

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-03-28 DOI: 10.1016/j.undsp.2025.01.002

Shuo Yu , Hao Jin , Liangjie Gu , Peng Gui

Stray current can cause corrosion of underground structural rebar, adding rubber particles to the invert-filling concrete is an effective prevent method to reduce stray current corrosion. In our research, the corrosion calculation model of multi-ring shield tunnel containing rubber concrete invert-filling was established, the coupling analysis of electric field and chemical field in composite structures was realized through mesoscale simulations, and the accuracy of calculation model was verified by full-scale test. Through calculation, the corrosion characteristic of segment rebar and bolt of multi-ring shield tunnel were investigated under different rubber content. The result shows that adding rubber particles to the invert-filling can not only reduce the corrosion current density of segment rebar and tunnel bolt effectively, but also affect the distribution form of rebar corrosion current density in both circumferential and longitudinal directions. When the rubber content increases from 5% to 20%, the maximum corrosion density of segment rebar and tunnel bolt will decrease from 31% to 58% and 30% to 32%, respectively. Under different stray current leakage modes, when the rubber content and input voltage are the same, the segment and bolt corrosion current density under single rail-two points leakage mode is greater than that in the two rails-single point leakage mode.

{"title":"Corrosion characteristic of multi-ring shield tunnel containing rubber concrete invert-filling under direct stray current","authors":"Shuo Yu , Hao Jin , Liangjie Gu , Peng Gui","doi":"10.1016/j.undsp.2025.01.002","DOIUrl":"10.1016/j.undsp.2025.01.002","url":null,"abstract":"<div><div>Stray current can cause corrosion of underground structural rebar, adding rubber particles to the invert-filling concrete is an effective prevent method to reduce stray current corrosion. In our research, the corrosion calculation model of multi-ring shield tunnel containing rubber concrete invert-filling was established, the coupling analysis of electric field and chemical field in composite structures was realized through mesoscale simulations, and the accuracy of calculation model was verified by full-scale test. Through calculation, the corrosion characteristic of segment rebar and bolt of multi-ring shield tunnel were investigated under different rubber content. The result shows that adding rubber particles to the invert-filling can not only reduce the corrosion current density of segment rebar and tunnel bolt effectively, but also affect the distribution form of rebar corrosion current density in both circumferential and longitudinal directions. When the rubber content increases from 5% to 20%, the maximum corrosion density of segment rebar and tunnel bolt will decrease from 31% to 58% and 30% to 32%, respectively. Under different stray current leakage modes, when the rubber content and input voltage are the same, the segment and bolt corrosion current density under single rail-two points leakage mode is greater than that in the two rails-single point leakage mode.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 337-354"},"PeriodicalIF":8.2,"publicationDate":"2025-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808239","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}

引用次数: 0

Shield tunneling efficiency and stability enhancement based on interpretable machine learning and multi-objective optimization

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-03-27 DOI: 10.1016/j.undsp.2025.01.001

Wenli Liu , Yang Chen , Tianxiang Liu , Wen Liu , Jue Li , Yangyang Chen

Adequate control of shield machine parameters to ensure the safety and efficiency of shield construction is a difficult and complex problem. To address this problem, this paper proposes a hybrid intelligent optimization framework that combines interpretable machine learning, intelligent optimization algorithms, and multi-objective optimization and decision-making methods. The nonlinear relationship between the input parameters and ground settlement (GS) is fitted based on the light gradient boosting machine (LGBM), and the effect of the input parameters on GS is analysed based on SHapley additive exPlanation for further feature selection. Subsequently, the hyperparameters of LGBM were determined based on the sparrow search algorithm (SSA) to better fit the input–output relationship. On this basis, a multi-objective intelligent optimization model is established to solve the optimized operating parameters of shield machine by non-dominated sorting genetic algorithm II and technique for order preference by similarity to ideal solution to reduce GS and improve drilling efficiency. The results demonstrate that the SSA-LGBM model predicts GS with high accuracy, exhibiting an RMSE of 4.775, a VAF of 0.930 and an R² of 0.931. These metrics collectively reflect the model’s excellent performance in prediction accuracy, ability to explain data variability, and control of prediction bias. The multi-objective optimization model is effective in optimizing two objectives, and the improvement can reach up to 39.38%; at the same time, the model has high scalability and can also be applied to three or more objectives. The intelligent optimization framework for shield construction parameters proposed in this paper can generate the optimal parameter combinations for shield machine manipulation, and provide reference and guidance when there are conflicting optimization objectives.

{"title":"Shield tunneling efficiency and stability enhancement based on interpretable machine learning and multi-objective optimization","authors":"Wenli Liu , Yang Chen , Tianxiang Liu , Wen Liu , Jue Li , Yangyang Chen","doi":"10.1016/j.undsp.2025.01.001","DOIUrl":"10.1016/j.undsp.2025.01.001","url":null,"abstract":"<div><div>Adequate control of shield machine parameters to ensure the safety and efficiency of shield construction is a difficult and complex problem. To address this problem, this paper proposes a hybrid intelligent optimization framework that combines interpretable machine learning, intelligent optimization algorithms, and multi-objective optimization and decision-making methods. The nonlinear relationship between the input parameters and ground settlement (GS) is fitted based on the light gradient boosting machine (LGBM), and the effect of the input parameters on GS is analysed based on SHapley additive exPlanation for further feature selection. Subsequently, the hyperparameters of LGBM were determined based on the sparrow search algorithm (SSA) to better fit the input–output relationship. On this basis, a multi-objective intelligent optimization model is established to solve the optimized operating parameters of shield machine by non-dominated sorting genetic algorithm II and technique for order preference by similarity to ideal solution to reduce GS and improve drilling efficiency. The results demonstrate that the SSA-LGBM model predicts GS with high accuracy, exhibiting an RMSE of 4.775, a VAF of 0.930 and an <em>R</em><sup>2</sup> of 0.931. These metrics collectively reflect the model’s excellent performance in prediction accuracy, ability to explain data variability, and control of prediction bias. The multi-objective optimization model is effective in optimizing two objectives, and the improvement can reach up to 39.38%; at the same time, the model has high scalability and can also be applied to three or more objectives. The intelligent optimization framework for shield construction parameters proposed in this paper can generate the optimal parameter combinations for shield machine manipulation, and provide reference and guidance when there are conflicting optimization objectives.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 320-336"},"PeriodicalIF":8.2,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143808238","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}

引用次数: 0

Optimization of reinforced ring base depth for vertical shaft sinking in soft soil using VSM method

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-03-19 DOI: 10.1016/j.undsp.2024.12.005

Dhyaa A.H. Abualghethe , Baogang Mu , Guoliang Dai , Sijin Liu , Zhongwei Li , Songyu Liu , Lei Han

Constructing vertical shafts in densely populated urban areas with complex geological conditions poses significant challenges, necessitating innovative construction techniques and design optimization. This study investigates the deformation behavior of a 42.5 m deep shaft excavated using the vertical shaft sinking machine (VSM) method in Shanghai’s soft soil conditions comprising deep cohesive soil layers. Comprehensive numerical analysis simulated the VSM construction process, analysing deformations within the shaft structure, surrounding soil, and adjacent buildings while evaluating the influence of varying reinforced ring base depths. Results reveal a significant 30% reduction in the maximum lateral shaft deformation, from 28 to 20 mm, by increasing the reinforced ring base depth to an optimal 16 m, enhancing lateral stability. Vertical deformations exhibited complex settlement and uplift mechanisms in segmental rings and piles, influenced by factors like excavation stages, pile installation, water pressures, and adjacent loads. The optimal 16 m depth effectively mitigated uplift, and optimized load distribution, limiting the maximum settlement to 12 mm while minimizing dewatering-induced uplift effects. Analysis indicated reduced lateral movements and settlements in surrounding buildings with increasing distance from excavation, highlighting VSM’s potential for minimizing impacts on neighboring structures. This study emphasizes VSM’s suitability for shaft projects in geologically complex areas, providing insights for design, mitigating environmental impacts, and enhancing deep excavation safety and efficiency in soft soils. The findings contribute to optimizing vertical shaft construction, ensuring successful underground infrastructure execution in challenging conditions. Identifying the optimal reinforced ring base depth promotes sustainable urban development by minimizing disturbances. This research advances innovative methods and strategies for complex underground projects.

{"title":"Optimization of reinforced ring base depth for vertical shaft sinking in soft soil using VSM method","authors":"Dhyaa A.H. Abualghethe , Baogang Mu , Guoliang Dai , Sijin Liu , Zhongwei Li , Songyu Liu , Lei Han","doi":"10.1016/j.undsp.2024.12.005","DOIUrl":"10.1016/j.undsp.2024.12.005","url":null,"abstract":"<div><div>Constructing vertical shafts in densely populated urban areas with complex geological conditions poses significant challenges, necessitating innovative construction techniques and design optimization. This study investigates the deformation behavior of a 42.5 m deep shaft excavated using the vertical shaft sinking machine (VSM) method in Shanghai’s soft soil conditions comprising deep cohesive soil layers. Comprehensive numerical analysis simulated the VSM construction process, analysing deformations within the shaft structure, surrounding soil, and adjacent buildings while evaluating the influence of varying reinforced ring base depths. Results reveal a significant 30% reduction in the maximum lateral shaft deformation, from 28 to 20 mm, by increasing the reinforced ring base depth to an optimal 16 m, enhancing lateral stability. Vertical deformations exhibited complex settlement and uplift mechanisms in segmental rings and piles, influenced by factors like excavation stages, pile installation, water pressures, and adjacent loads. The optimal 16 m depth effectively mitigated uplift, and optimized load distribution, limiting the maximum settlement to 12 mm while minimizing dewatering-induced uplift effects. Analysis indicated reduced lateral movements and settlements in surrounding buildings with increasing distance from excavation, highlighting VSM’s potential for minimizing impacts on neighboring structures. This study emphasizes VSM’s suitability for shaft projects in geologically complex areas, providing insights for design, mitigating environmental impacts, and enhancing deep excavation safety and efficiency in soft soils. The findings contribute to optimizing vertical shaft construction, ensuring successful underground infrastructure execution in challenging conditions. Identifying the optimal reinforced ring base depth promotes sustainable urban development by minimizing disturbances. This research advances innovative methods and strategies for complex underground projects.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 280-302"},"PeriodicalIF":8.2,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143748524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Cutting-edge approaches to specific energy prediction in TBM disc cutters: Integrating COSSA-RF model with three interpretative techniques

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-03-10 DOI: 10.1016/j.undsp.2024.11.004

Jian Zhou , Zijian Liu , Chuanqi Li , Kun Du , Haiqing Yang

Specific energy (SE) is an important index to measure crushing efficiency in mechanized tunnel excavation. Accurate prediction of the SE of tunnel boring machine disc cutters is important for optimizing the crushing process, reducing energy consumption, and minimizing machine wear. Therefore, in this paper, the sparrow search algorithm (SSA), combined with six chaotic mapping strategies, is utilized to optimize the random forest (RF) model for predicting SE, referred to as the COSSA-RF prediction models. For this purpose, an SE prediction database was established for training and validating model performance, encompassing 160 sets of experimental data, each with six input parameters: uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), disc cutter diameter (D), cutter tip width (T), cutter spacing (S), and cutter penetration depth (P), along with a target parameter, SE. The evaluation results indicate that the COSSA-RF models demonstrate superior performance compared to other four machine learning models. In particular, the Chebyshev map-SSA-RF (CHSSA-RF) model achieves the most satisfactory prediction accuracy among all models, resulting in the highest coefficient of determination R² and dynamic variance-weighted global performance indicator values (0.9756 and 0.0814) and the lowest values of root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) (6.4742, 4.0003, and 20.41%). Lastly, the results of interpretability analysis of the best model through SHapley Additive exPlanations, local interpretable model-agnostic explanations, and Vivid methods show that the importance of input parameters ranked as follows: UCS, BTS, P, S, T, and D. Moreover, interactions between parameters (UCS and BTS, BTS and P, and BTS and S) significantly influence the model predictions.

{"title":"Cutting-edge approaches to specific energy prediction in TBM disc cutters: Integrating COSSA-RF model with three interpretative techniques","authors":"Jian Zhou , Zijian Liu , Chuanqi Li , Kun Du , Haiqing Yang","doi":"10.1016/j.undsp.2024.11.004","DOIUrl":"10.1016/j.undsp.2024.11.004","url":null,"abstract":"<div><div>Specific energy (SE) is an important index to measure crushing efficiency in mechanized tunnel excavation. Accurate prediction of the SE of tunnel boring machine disc cutters is important for optimizing the crushing process, reducing energy consumption, and minimizing machine wear. Therefore, in this paper, the sparrow search algorithm (SSA), combined with six chaotic mapping strategies, is utilized to optimize the random forest (RF) model for predicting SE, referred to as the COSSA-RF prediction models. For this purpose, an SE prediction database was established for training and validating model performance, encompassing 160 sets of experimental data, each with six input parameters: uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), disc cutter diameter (<em>D</em>), cutter tip width (<em>T</em>), cutter spacing (<em>S</em>), and cutter penetration depth (<em>P</em>), along with a target parameter, SE. The evaluation results indicate that the COSSA-RF models demonstrate superior performance compared to other four machine learning models. In particular, the Chebyshev map-SSA-RF (CHSSA-RF) model achieves the most satisfactory prediction accuracy among all models, resulting in the highest coefficient of determination <em>R</em><sup>2</sup> and dynamic variance-weighted global performance indicator values (0.9756 and 0.0814) and the lowest values of root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) (6.4742, 4.0003, and 20.41%). Lastly, the results of interpretability analysis of the best model through SHapley Additive exPlanations, local interpretable model-agnostic explanations, and Vivid methods show that the importance of input parameters ranked as follows: UCS, BTS, <em>P</em>, <em>S</em>, <em>T</em>, and <em>D</em>. Moreover, interactions between parameters (UCS and BTS, BTS and <em>P</em>, and BTS and <em>S</em>) significantly influence the model predictions.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 241-262"},"PeriodicalIF":8.2,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Field monitoring and instrumentation in microtunnelling/pipe jacking: A review and future directions

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-02-25 DOI: 10.1016/j.undsp.2024.12.003

Asad Wadood , Bryan A. McCabe , Brian B. Sheil

The popularity of trenchless techniques as a means of utility pipeline installation in urban environments, specifically microtunnelling/pipe-jacking, has increased in recent years due to its minimally-disruptive nature and reduced carbon footprint in comparison to conventional open-cut excavation methods. The response of pipes during the jacking process is complex and is governed by several factors, including ground conditions, the amount and distribution of lubrication, pipe and annulus size, pipeline misalignments and jacking force eccentricity, among others. Design practice remains based on empirical equations and previous drives through similar geology, resulting in uncertainty in jacking force estimates, thereby restricting adoption of the technique. In order to improve our understanding of the pipe-jacking process, pipes incorporating sensors providing real-time measurements of earth pressures, pore water pressures, axial strains and hoop strains can be used; but the number of such studies reported in the literature is small and the potential of instrumentation on routine projects is largely untapped. Moreover, jacking pipe monitoring practice lags behind the state-of-the-art instrumentation techniques used for monitoring other geotechnical infrastructure. The purpose of this paper is to provide a thorough review of learnings from instrumented pipe-jacking case studies and other supporting research, as well as to propose potential solutions to research gaps in the current state of design practice and field monitoring of pipe jacking projects.

{"title":"Field monitoring and instrumentation in microtunnelling/pipe jacking: A review and future directions","authors":"Asad Wadood , Bryan A. McCabe , Brian B. Sheil","doi":"10.1016/j.undsp.2024.12.003","DOIUrl":"10.1016/j.undsp.2024.12.003","url":null,"abstract":"<div><div>The popularity of trenchless techniques as a means of utility pipeline installation in urban environments, specifically microtunnelling/pipe-jacking, has increased in recent years due to its minimally-disruptive nature and reduced carbon footprint in comparison to conventional open-cut excavation methods. The response of pipes during the jacking process is complex and is governed by several factors, including ground conditions, the amount and distribution of lubrication, pipe and annulus size, pipeline misalignments and jacking force eccentricity, among others. Design practice remains based on empirical equations and previous drives through similar geology, resulting in uncertainty in jacking force estimates, thereby restricting adoption of the technique. In order to improve our understanding of the pipe-jacking process, pipes incorporating sensors providing real-time measurements of earth pressures, pore water pressures, axial strains and hoop strains can be used; but the number of such studies reported in the literature is small and the potential of instrumentation on routine projects is largely untapped. Moreover, jacking pipe monitoring practice lags behind the state-of-the-art instrumentation techniques used for monitoring other geotechnical infrastructure. The purpose of this paper is to provide a thorough review of learnings from instrumented pipe-jacking case studies and other supporting research, as well as to propose potential solutions to research gaps in the current state of design practice and field monitoring of pipe jacking projects.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 225-240"},"PeriodicalIF":8.2,"publicationDate":"2025-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143643908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Test and field application of fracture evolution of large-span tunnel under NPR bolt compensation support system NPR 螺栓补偿支撑系统下大跨度隧道断裂演化试验与现场应用

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-02-15 DOI: 10.1016/j.undsp.2024.12.002

Jun Yang , Kexue Wang , Wenhui Bian , Yanbo Zhang , Xiaohui He , Yi Fang , Zhicheng Sun

Shallow-buried large-span tunnels may bend or collapse owing to loads, and their surface structures present considerable safety issues. At Huashanyilu station on Qingdao Metro Line 6 in China, theoretical studies and interior model tests were conducted to effectively increase the bearing capacity of the tunnel. The anchoring bearing mechanism of the high prestress compensating support system was revealed, and the system was built using a negative Poisson’s ratio (NPR) bolt at its core. We compared and analyzed the fracture evolution characteristics of the compensating and conventional support systems under various loads. The results showed that the compensating support system effectively increased the support strength and residual safety factor of the bearing arch, whereas the use of a high-prestress NPR anchor reduced the early deformation of the surrounding rock. The coupling failure modes of the arch tension extrusion failure and arch foot shear fracture occurred when the tunnel surrounding the rock was overloaded. The compensatory support system produces a bearing arch that is extremely resistant to external loads with minimal deformation of the tunnel surface and arch frame, excellent surrounding rock integrity, and a low stress rate. The radial and tangential peak stresses exceeded those of the passive support system, and the structural block fell when it became unstable. The maximum displacement of the arch stays constant at −5.7 mm after tunnel excavation. NPR bolts have remarkable applications in this field. The conclusions of this study have a significant impact on the regulation of the stability of the surrounding rock in large-span tunnels.

{"title":"Test and field application of fracture evolution of large-span tunnel under NPR bolt compensation support system","authors":"Jun Yang , Kexue Wang , Wenhui Bian , Yanbo Zhang , Xiaohui He , Yi Fang , Zhicheng Sun","doi":"10.1016/j.undsp.2024.12.002","DOIUrl":"10.1016/j.undsp.2024.12.002","url":null,"abstract":"<div><div>Shallow-buried large-span tunnels may bend or collapse owing to loads, and their surface structures present considerable safety issues. At Huashanyilu station on Qingdao Metro Line 6 in China, theoretical studies and interior model tests were conducted to effectively increase the bearing capacity of the tunnel. The anchoring bearing mechanism of the high prestress compensating support system was revealed, and the system was built using a negative Poisson’s ratio (NPR) bolt at its core. We compared and analyzed the fracture evolution characteristics of the compensating and conventional support systems under various loads. The results showed that the compensating support system effectively increased the support strength and residual safety factor of the bearing arch, whereas the use of a high-prestress NPR anchor reduced the early deformation of the surrounding rock. The coupling failure modes of the arch tension extrusion failure and arch foot shear fracture occurred when the tunnel surrounding the rock was overloaded. The compensatory support system produces a bearing arch that is extremely resistant to external loads with minimal deformation of the tunnel surface and arch frame, excellent surrounding rock integrity, and a low stress rate. The radial and tangential peak stresses exceeded those of the passive support system, and the structural block fell when it became unstable. The maximum displacement of the arch stays constant at −5.7 mm after tunnel excavation. NPR bolts have remarkable applications in this field. The conclusions of this study have a significant impact on the regulation of the stability of the surrounding rock in large-span tunnels.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 186-207"},"PeriodicalIF":8.2,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Overall smoke control performance using naturally ventilated shafts in tunnel fires with multiple fire sources

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-02-13 DOI: 10.1016/j.undsp.2024.10.005

Kun He , Ying Zhen Li , Haukur Ingason , Xudong Cheng

This study investigates the overall smoke control performance using shafts in a naturally ventilated tunnel in the case of multiple fire sources. Detailed comparisons were also made with the corresponding single fire source scenarios. The results show that the interaction between multiple fire sources affects smoke control performance, resulting in a lower smoke layer height compared to the corresponding single fire scenario. For the multiple fire sources scenarios, the smoke layer height in the fire section first decreases and then keeps stable, as the fire center spacing increases. The smoke layer height in the fire section is 20%–25% lower than that in a single fire source scenario for a given total heat release rate. The minimum smoke layer height at the adjacent non-fire tunnel section is much lower than that in the fire section due to the disturbance of the first group of shafts. For a small tunnel fire such as a car fire, the critical safety distances for firefighters and evacuees increase as the fire source spacing decreases. For a large tunnel fire such as a bus fire, the effect of fire source spacing on the critical safety distance is limited, while the shaft interval plays an important role. The fire source spacing and the number of fire sources have limited influences on the smoke spread length due to the small differences in the induced air flow velocity and overall smoke exhaust rate through shafts. When the fire sources are located under one shaft, the number of shafts required for complete smoke exhaust is the least and the total smoke spread length is the shortest. For a given fire location, the smoke spread length increases significantly with an increasing shaft interval. This study contributes to the design of natural ventilation shafts in tunnels possibly with multiple fire sources.

{"title":"Overall smoke control performance using naturally ventilated shafts in tunnel fires with multiple fire sources","authors":"Kun He , Ying Zhen Li , Haukur Ingason , Xudong Cheng","doi":"10.1016/j.undsp.2024.10.005","DOIUrl":"10.1016/j.undsp.2024.10.005","url":null,"abstract":"<div><div>This study investigates the overall smoke control performance using shafts in a naturally ventilated tunnel in the case of multiple fire sources. Detailed comparisons were also made with the corresponding single fire source scenarios. The results show that the interaction between multiple fire sources affects smoke control performance, resulting in a lower smoke layer height compared to the corresponding single fire scenario. For the multiple fire sources scenarios, the smoke layer height in the fire section first decreases and then keeps stable, as the fire center spacing increases. The smoke layer height in the fire section is 20%–25% lower than that in a single fire source scenario for a given total heat release rate. The minimum smoke layer height at the adjacent non-fire tunnel section is much lower than that in the fire section due to the disturbance of the first group of shafts. For a small tunnel fire such as a car fire, the critical safety distances for firefighters and evacuees increase as the fire source spacing decreases. For a large tunnel fire such as a bus fire, the effect of fire source spacing on the critical safety distance is limited, while the shaft interval plays an important role. The fire source spacing and the number of fire sources have limited influences on the smoke spread length due to the small differences in the induced air flow velocity and overall smoke exhaust rate through shafts. When the fire sources are located under one shaft, the number of shafts required for complete smoke exhaust is the least and the total smoke spread length is the shortest. For a given fire location, the smoke spread length increases significantly with an increasing shaft interval. This study contributes to the design of natural ventilation shafts in tunnels possibly with multiple fire sources.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 168-185"},"PeriodicalIF":8.2,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143620458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Evaluation of greenhouse gas emissions in subway tunnel construction

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-02-11 DOI: 10.1016/j.undsp.2024.12.001

Yalin Guo , Chen Dong , Zheng Chen , Shulei Zhao , Wenhao Sun , Wei He , Lei Zhang , Yiyuan Wang , Nan Hu , Chun Guo

This study evaluates the greenhouse gas (GHG) emissions associated with the construction of subway tunnels, aiming to identify the primary sources of emissions and provide insights into emission reduction strategies. Using the civil engineering construction of specific tunnels of a subway line in Guangdong Province, China, as a case study, this research quantitatively analyzes the composition of GHG emissions across three stages: upstream building materials production, building materials transportation, and on-site construction. The results indicate that upstream building materials production and on-site construction collectively account for over 95% of the total GHG emissions during tunnel construction. The analysis further reveals that a small proportion of building materials and construction machinery accounts for the majority of total GHG emissions during tunnel construction, aligning with the Pareto principle. The findings emphasize the importance of accurate evaluation of high-impact building materials and construction machinery, particularly in contexts where basic energy consumption data are limited. Strategies such as utilizing recycled materials and enhancing machinery efficiency can lead to significant emission reductions. For instance, achieving a recycling rate of 10% to 30% for steel and concrete can reduce total GHG emissions from tunnel construction by 5.51% to 9.94%, while improving machinery efficiency by 10% to 30% can reduce emissions by up to 2.29%. These findings provide a scientific basis for low-carbon subway tunnel construction.

{"title":"Evaluation of greenhouse gas emissions in subway tunnel construction","authors":"Yalin Guo , Chen Dong , Zheng Chen , Shulei Zhao , Wenhao Sun , Wei He , Lei Zhang , Yiyuan Wang , Nan Hu , Chun Guo","doi":"10.1016/j.undsp.2024.12.001","DOIUrl":"10.1016/j.undsp.2024.12.001","url":null,"abstract":"<div><div>This study evaluates the greenhouse gas (GHG) emissions associated with the construction of subway tunnels, aiming to identify the primary sources of emissions and provide insights into emission reduction strategies. Using the civil engineering construction of specific tunnels of a subway line in Guangdong Province, China, as a case study, this research quantitatively analyzes the composition of GHG emissions across three stages: upstream building materials production, building materials transportation, and on-site construction. The results indicate that upstream building materials production and on-site construction collectively account for over 95% of the total GHG emissions during tunnel construction. The analysis further reveals that a small proportion of building materials and construction machinery accounts for the majority of total GHG emissions during tunnel construction, aligning with the Pareto principle. The findings emphasize the importance of accurate evaluation of high-impact building materials and construction machinery, particularly in contexts where basic energy consumption data are limited. Strategies such as utilizing recycled materials and enhancing machinery efficiency can lead to significant emission reductions. For instance, achieving a recycling rate of 10% to 30% for steel and concrete can reduce total GHG emissions from tunnel construction by 5.51% to 9.94%, while improving machinery efficiency by 10% to 30% can reduce emissions by up to 2.29%. These findings provide a scientific basis for low-carbon subway tunnel construction.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 263-279"},"PeriodicalIF":8.2,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143686442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experimental study on the modulus of soil reaction for plastic pipes buried in lightweight cellular concrete backfill

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2025-01-23 DOI: 10.1016/j.undsp.2024.11.003

Yu-qiu Ye , Jie Han , Brad Dolton , Md Wasif Zaman , Robert L. Parsons

The modulus of soil reaction, representing the stiffness of a soil surrounding pipes, is a critical parameter in the design of buried flexible pipes. This study conducted plate loading tests on corrugated polyvinyl chloride, smooth polyvinyl chloride, and high-density polyethylene pipes buried in lightweight cellular concrete (LCC) backfills at densities of 400, 475, 550, and 650 kg/m³ to investigate the pipe deformation behavior and moduli of soil reaction. In addition, this study examined the effects of the narrow trench condition on the pipe deformation and modulus of soil reaction. In these tests, the vertical and horizontal diameter changes of pipes under the vertical pressures applied through a hydraulic jack were measured. Test results reveal that the average moduli of soil reaction of plastic pipes within a wide trench backfilled by the LCCs at densities of 400, 475, 550, and 650 kg/m³ were back-calculated as 66, 99, 133, and 205 MPa, respectively, using the modified Iowa formula. Furthermore, the back-calculated moduli of soil reaction for LCCs exhibited linear relationships with their densities and unconfined compressive strengths and were higher than the recommended values for the commonly used soil backfills. Based on the vertical deformation criterion of 5% pipe diameter, the ultimate bearing capacities of flexible pipes buried in wide LCCs at densities of 475, 550, and 650 kg/m³ exceeded 500 kPa. The LCC with a narrow trench exhibited a lower modulus of soil reaction and ultimate bearing capacity but a larger pipe diameter change.

{"title":"Experimental study on the modulus of soil reaction for plastic pipes buried in lightweight cellular concrete backfill","authors":"Yu-qiu Ye , Jie Han , Brad Dolton , Md Wasif Zaman , Robert L. Parsons","doi":"10.1016/j.undsp.2024.11.003","DOIUrl":"10.1016/j.undsp.2024.11.003","url":null,"abstract":"<div><div>The modulus of soil reaction, representing the stiffness of a soil surrounding pipes, is a critical parameter in the design of buried flexible pipes. This study conducted plate loading tests on corrugated polyvinyl chloride, smooth polyvinyl chloride, and high-density polyethylene pipes buried in lightweight cellular concrete (LCC) backfills at densities of 400, 475, 550, and 650 kg/m<sup>3</sup> to investigate the pipe deformation behavior and moduli of soil reaction. In addition, this study examined the effects of the narrow trench condition on the pipe deformation and modulus of soil reaction. In these tests, the vertical and horizontal diameter changes of pipes under the vertical pressures applied through a hydraulic jack were measured. Test results reveal that the average moduli of soil reaction of plastic pipes within a wide trench backfilled by the LCCs at densities of 400, 475, 550, and 650 kg/m<sup>3</sup> were back-calculated as 66, 99, 133, and 205 MPa, respectively, using the modified Iowa formula. Furthermore, the back-calculated moduli of soil reaction for LCCs exhibited linear relationships with their densities and unconfined compressive strengths and were higher than the recommended values for the commonly used soil backfills. Based on the vertical deformation criterion of 5% pipe diameter, the ultimate bearing capacities of flexible pipes buried in wide LCCs at densities of 475, 550, and 650 kg/m<sup>3</sup> exceeded 500 kPa. The LCC with a narrow trench exhibited a lower modulus of soil reaction and ultimate bearing capacity but a larger pipe diameter change.</div></div>","PeriodicalId":48505,"journal":{"name":"Underground Space","volume":"22 ","pages":"Pages 153-167"},"PeriodicalIF":8.2,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143610619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0