To evaluate the effects of possible ground explosion on a shallow-buried metro tunnel, this paper attempts to analyze the dynamic responses of the operating metro tunnel in soft soil, using a widely applied explicit d...To evaluate the effects of possible ground explosion on a shallow-buried metro tunnel, this paper attempts to analyze the dynamic responses of the operating metro tunnel in soft soil, using a widely applied explicit dynamic nonlinear finite element software ANSYS/LS-DYNA. The blast induced wave propagation in the soil and the tunnel, and the von Mises effective stress and acceleration of the tunnel lining were presented, and the safety of the tunnel lining was evaluated based on the failure criterion. Besides, the parametric study of the soil was also carried out. The numerical results indicate that the upper part of the tunnel lining cross-section with directions ranging from 0° to 22.5° and horizontal distances 0 to 7 m away from the explosive center are the vulnerable areas, and the metro tunnel might be safe when tunnel depth is more than 7 m and TNT charge on the ground is no more than 500 kg, and the selection of soil parameters should be paid more attentions to conduct a more precise analysis.展开更多
Stratum deformation(settlement) is a challenging issue in tunnel engineering, especially when construction of metro tunnels has to undercut high-speed railway. For this purpose, we used the FLAC30 software to analyze ...Stratum deformation(settlement) is a challenging issue in tunnel engineering, especially when construction of metro tunnels has to undercut high-speed railway. For this purpose, we used the FLAC30 software to analyze the stratum settlement characteristics of high-speed railway at different crossing angles intersected by metro tunnel, in terms of ground settlement trough, stratum slip line and irregularity of ballastless tracks. According to the evolution of the stratum settlement at different angle regions, an optimized angle is proposed for the actual project design. In order to reduce the influence of stratum settlement on the safety of high-speed railway, an approach of safety assessment is proposed for the shield engineering undercutting high-speed railway, as per Chinese specifications using numerical results and on-site conditions. A case study is conducted for the shield tunnel section crossing the Wuhan-Guangzhou High-speed Railway between the Guangzhou North Railway Station and the Huacheng Road Station, which represents the first metro tunnel project passing below a high-speed railway in China. A series of measures is taken to ensure the safe excavation of the shield tunnel and the operation of the high-speed railway. The results can provide a technical support for performing a safety evaluation between high-speed railways and metro tunnels.展开更多
To choose the optimum construction method of metro tunneling,we conducted research with numerical simulation on strata consolidation subsidence by dewatering,dynamic dewatering,and non-dewatering construction method,t...To choose the optimum construction method of metro tunneling,we conducted research with numerical simulation on strata consolidation subsidence by dewatering,dynamic dewatering,and non-dewatering construction method,taking the integrated effects of fluid-solid coupling and tunneling mechanics into account.We obtained the curved surfaces of ground surface subsidence and strata consolidation subsidence.The results show that the quantity of ground surface subsidence is 31 mm for the non-dewatering method,39 mm for the dynamic dewatering method,and 105 mm for the dewatering method.Their ratio is 1:1.3:3.4;and the percentages of strata consolidation subsidence to whole ground surface subsidence of each construction method is 27(no-dewatering),50(dynamic dewatering),and 79(dewatering).It is obvious that the non-dewatering construction method is the most effective method to control the strata consolidation subsidence induced by metro tunneling in saturated soft clay strata,and it has been successfully applied to the construction of the Shenzhen metro line 1.展开更多
The application of jacked box tunnelling for underground passages has grown rapidly in recent years in China.In this study,the design of an extreme shallow jacked box tunnel traversing the underlying metro tunnels was...The application of jacked box tunnelling for underground passages has grown rapidly in recent years in China.In this study,the design of an extreme shallow jacked box tunnel traversing the underlying metro tunnels was introduced.An innovative additional soil filling above the ground surface was carried out to overcome the overlying-soil-carrying effect of the extreme shallow jacked box tunnelling.The structural safety of metro tunnels during the jacking process was analyzed through in-situ monitoring.It indicated that the overlying-soil-carrying effect was successfully alleviated.The metro tunnels generally showed horizontal displacement towards the receiving shaft,uplift and horizontal stretch during the jacking process.The stop of jacking machine in front of obstacles generally contributed to the decrease of horizontal displacement,uplift and horizontal stretch of metro tunnels.The largest horizontal displacement(1.3–1.6 mm),uplift(1.5 mm)and horizontal convergence(1.6–1.8 mm)generally occurred when the reception of jacking machine was completed,and they all met the requirement of 2 mm for this project.The design and construction of this shallow jacked box tunnel project could provide references for future similar projects.展开更多
The excavation of a foundation pit considerably affects the adjacent structures and underground pipelines owing to the change in the stress state of the surrounding soil,resulting in deformation.The study of an actual...The excavation of a foundation pit considerably affects the adjacent structures and underground pipelines owing to the change in the stress state of the surrounding soil,resulting in deformation.The study of an actual engineering case was conducted to examine the influence of excavation on the deformation of adjacent subway tunnels.The finite element analysis software PLAXIS 3D was used to simulate the entire excavation process.The structural design of the foundation pit was optimized based on the simulation results to ensure the stability of the foundation pit and the safety of the existing subway tunnel structure.Finally,the safety evaluation of the excavation of the foundation pit that caused the deformation of the adjacent subway tunnel was performed.The influence of the excavation and unloading of the foundation pit on the subway tunnel is closely related to the distance between the subway and the foundation pit,the amount of earthwork excavated at one time,and the engineering geological conditions.The results of this paper can provide useful reference for the design optimization and safety assessment of similar projects.展开更多
In this study,a two-dimensional(2D)soil–water coupling dynamicfinite element(FE)analysis is conducted to investigate the effect of repeated train vibrations on the long-term settlement of a metro tunnel in saturated c...In this study,a two-dimensional(2D)soil–water coupling dynamicfinite element(FE)analysis is conducted to investigate the effect of repeated train vibrations on the long-term settlement of a metro tunnel in saturated clay.Particular attention is paid to the leakage prob-lem of the metro tunnel by assuming different permeability conditions,namely fully permeable,fully impermeable,and partially perme-able,on the periphery of the tunnel for simplicity.The train vibration load isfirst evaluated using a rail–fastener–tunnel–subgrade model and averaged over a characteristic length for 2D numerical analysis.Cyclic Mobility model is used to simulate the mechanical behaviors of saturated soft clay in the FE analysis.Excess pore water pressure(EPWP)and associated tunnel settlement in trial operation and normal operation are calculated using the FE code DBLEAVES for different permeability conditions.It is found that a very low EPWP is generated in the trial operation,which then increases rapidly to peak values at the early days of normal operation.Afterward,the EPWP diminishes gradually as the train vibration continues.The permeability of the tunnel lining plays a significant role in the distri-bution of EPWP around the tunnel but produces a minor influence on the development of tunnel settlement.The train-induced tunnel settlement is mainly caused by the static settlement resulting from the EPWP dissipation during train interval,while the dynamic settle-ment arising from dynamic consolidation in each train vibration only accounts for a small portion.According to the 2D dynamic FE analysis,thefinal train-induced settlement of the metro tunnel in saturated clay is estimated to reach 160 mm while the peak EPWP value can reach 26.55 kPa.The settlement discrepancies between the numerical method and empirical method are discussed in detail.展开更多
Metro tunnels play a crucial role in urban transportation.However,with growing tunnel operation periods,defects,and large deformations appearing,these are influencing tunnel structural performance and threatening publ...Metro tunnels play a crucial role in urban transportation.However,with growing tunnel operation periods,defects,and large deformations appearing,these are influencing tunnel structural performance and threatening public safety.Three-dimensional(3D)tunnel reconstruction is an effective way to highlight tunnel conditions and provide a basis for engineering management and maintenance.However,the current methods of tunnel 3D reconstruction do not sufficiently combine the qualitative and quantitative characteristics of tunnel states.In this study,a novel method for metro tunnel 3D reconstruction based on structure from motion(SfM)and direct linear transformation(DLT)is proposed.The dimensionless 3D reconstruction point cloud acquired through the SfM method showcases the qualitative characteristics(such as leakage and pipelines)of the tunnel state.The close-range photogrammetry DLT method provides scale information missing from the SfM method and quantitative characteristics(such as profile deformation)of the tunnel state.The SfM-DLT method was tested in a Shanghai metro tunnel,and proved to be feasible and promising for future tunnel inspections.展开更多
Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in...Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.展开更多
Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combinin...Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combining the deep learning model and the 3D reconstruction method based on structure from motion(SfM),this paper proposes a novel SfM-Deep learning method for tunnel inspection.The high-quality 3D tunnel model is constructed by using images taken every 1 m along the longitudinal direction.The instance segmentation of leakage in longitudinal images is realized using the mask region-based convolutional neural network deep learning model.The SfM-Deep learning method projects the texture of the images after defect recognition to the 3D model and realizes the visualization of leakage defects.By projecting the model to the design cylindrical surface and expanding it,the tunnel leakage area is quantified.Through its practical application in a Shanghai metro shield tunnel,the reliability of the proposed method was verified.The novel SfM-Deep learning method can help engineers efficiently carry out intelligent tunnel detection.展开更多
Constructing a metro station by enlarging shield tunnels combined with a mining/cut-and-cover method provides a new method to solve the contradictions of construction time limits of shield tunnels and stations. As a n...Constructing a metro station by enlarging shield tunnels combined with a mining/cut-and-cover method provides a new method to solve the contradictions of construction time limits of shield tunnels and stations. As a new-style construction method, there are several specific risks involved in the construction process. Based on the test section of Sanyuanqiao station on Beijing metro line 10, and combined with the existing methods of risk identification at present, including a review of world-wide operational experience of similar projects, the study of generic guidance on hazards associated with the type of work being undertaken, and discussions with qualified and experienced staff from the project team, etc., the specific risks during the construction process of the metro station constructed by enlarging shield tunnels combined with the cut-and-cover method are identified. The results show that the specific risks mainly come from three construction processes which include constructing upper enclosure structures, excavating the soil between shield tunnels and demolishing shield segments. Then relevant risk mitigation measures are put forward. The results can provide references for scheme improvement and a comprehensive risk assessment of the new-style construction method.展开更多
基金Supported by the National Natural Science Foundation of China (40874074, 50950110347)the National High Technology Research and Development Program (863 Program) of China (2006AA11ZAA8)Shanghai Science and Technology Development Funds (07ZR14117)
文摘To evaluate the effects of possible ground explosion on a shallow-buried metro tunnel, this paper attempts to analyze the dynamic responses of the operating metro tunnel in soft soil, using a widely applied explicit dynamic nonlinear finite element software ANSYS/LS-DYNA. The blast induced wave propagation in the soil and the tunnel, and the von Mises effective stress and acceleration of the tunnel lining were presented, and the safety of the tunnel lining was evaluated based on the failure criterion. Besides, the parametric study of the soil was also carried out. The numerical results indicate that the upper part of the tunnel lining cross-section with directions ranging from 0° to 22.5° and horizontal distances 0 to 7 m away from the explosive center are the vulnerable areas, and the metro tunnel might be safe when tunnel depth is more than 7 m and TNT charge on the ground is no more than 500 kg, and the selection of soil parameters should be paid more attentions to conduct a more precise analysis.
基金the National Natural Science Foundation of China(Grant Nos. 51278423 and 51478395)for its financial support
文摘Stratum deformation(settlement) is a challenging issue in tunnel engineering, especially when construction of metro tunnels has to undercut high-speed railway. For this purpose, we used the FLAC30 software to analyze the stratum settlement characteristics of high-speed railway at different crossing angles intersected by metro tunnel, in terms of ground settlement trough, stratum slip line and irregularity of ballastless tracks. According to the evolution of the stratum settlement at different angle regions, an optimized angle is proposed for the actual project design. In order to reduce the influence of stratum settlement on the safety of high-speed railway, an approach of safety assessment is proposed for the shield engineering undercutting high-speed railway, as per Chinese specifications using numerical results and on-site conditions. A case study is conducted for the shield tunnel section crossing the Wuhan-Guangzhou High-speed Railway between the Guangzhou North Railway Station and the Huacheng Road Station, which represents the first metro tunnel project passing below a high-speed railway in China. A series of measures is taken to ensure the safe excavation of the shield tunnel and the operation of the high-speed railway. The results can provide a technical support for performing a safety evaluation between high-speed railways and metro tunnels.
文摘To choose the optimum construction method of metro tunneling,we conducted research with numerical simulation on strata consolidation subsidence by dewatering,dynamic dewatering,and non-dewatering construction method,taking the integrated effects of fluid-solid coupling and tunneling mechanics into account.We obtained the curved surfaces of ground surface subsidence and strata consolidation subsidence.The results show that the quantity of ground surface subsidence is 31 mm for the non-dewatering method,39 mm for the dynamic dewatering method,and 105 mm for the dewatering method.Their ratio is 1:1.3:3.4;and the percentages of strata consolidation subsidence to whole ground surface subsidence of each construction method is 27(no-dewatering),50(dynamic dewatering),and 79(dewatering).It is obvious that the non-dewatering construction method is the most effective method to control the strata consolidation subsidence induced by metro tunneling in saturated soft clay strata,and it has been successfully applied to the construction of the Shenzhen metro line 1.
基金supported by the Construction Research Project of Zhejiang Province,China(Grant Nos.2021K167 and 2021K103)Science and Technology Innovation Project of Zhejiang Province,China(Grant No.2019R52035)Research Funding of Dongtong Geotechnical Technology Co.,Ltd.,China.
文摘The application of jacked box tunnelling for underground passages has grown rapidly in recent years in China.In this study,the design of an extreme shallow jacked box tunnel traversing the underlying metro tunnels was introduced.An innovative additional soil filling above the ground surface was carried out to overcome the overlying-soil-carrying effect of the extreme shallow jacked box tunnelling.The structural safety of metro tunnels during the jacking process was analyzed through in-situ monitoring.It indicated that the overlying-soil-carrying effect was successfully alleviated.The metro tunnels generally showed horizontal displacement towards the receiving shaft,uplift and horizontal stretch during the jacking process.The stop of jacking machine in front of obstacles generally contributed to the decrease of horizontal displacement,uplift and horizontal stretch of metro tunnels.The largest horizontal displacement(1.3–1.6 mm),uplift(1.5 mm)and horizontal convergence(1.6–1.8 mm)generally occurred when the reception of jacking machine was completed,and they all met the requirement of 2 mm for this project.The design and construction of this shallow jacked box tunnel project could provide references for future similar projects.
基金the National Natural Science Foundation Project of China(grant number:51768040 and 51508256).
文摘The excavation of a foundation pit considerably affects the adjacent structures and underground pipelines owing to the change in the stress state of the surrounding soil,resulting in deformation.The study of an actual engineering case was conducted to examine the influence of excavation on the deformation of adjacent subway tunnels.The finite element analysis software PLAXIS 3D was used to simulate the entire excavation process.The structural design of the foundation pit was optimized based on the simulation results to ensure the stability of the foundation pit and the safety of the existing subway tunnel structure.Finally,the safety evaluation of the excavation of the foundation pit that caused the deformation of the adjacent subway tunnel was performed.The influence of the excavation and unloading of the foundation pit on the subway tunnel is closely related to the distance between the subway and the foundation pit,the amount of earthwork excavated at one time,and the engineering geological conditions.The results of this paper can provide useful reference for the design optimization and safety assessment of similar projects.
基金supported by the Natural Science Foundation of China(NSFC Grant No.51538009)。
文摘In this study,a two-dimensional(2D)soil–water coupling dynamicfinite element(FE)analysis is conducted to investigate the effect of repeated train vibrations on the long-term settlement of a metro tunnel in saturated clay.Particular attention is paid to the leakage prob-lem of the metro tunnel by assuming different permeability conditions,namely fully permeable,fully impermeable,and partially perme-able,on the periphery of the tunnel for simplicity.The train vibration load isfirst evaluated using a rail–fastener–tunnel–subgrade model and averaged over a characteristic length for 2D numerical analysis.Cyclic Mobility model is used to simulate the mechanical behaviors of saturated soft clay in the FE analysis.Excess pore water pressure(EPWP)and associated tunnel settlement in trial operation and normal operation are calculated using the FE code DBLEAVES for different permeability conditions.It is found that a very low EPWP is generated in the trial operation,which then increases rapidly to peak values at the early days of normal operation.Afterward,the EPWP diminishes gradually as the train vibration continues.The permeability of the tunnel lining plays a significant role in the distri-bution of EPWP around the tunnel but produces a minor influence on the development of tunnel settlement.The train-induced tunnel settlement is mainly caused by the static settlement resulting from the EPWP dissipation during train interval,while the dynamic settle-ment arising from dynamic consolidation in each train vibration only accounts for a small portion.According to the 2D dynamic FE analysis,thefinal train-induced settlement of the metro tunnel in saturated clay is estimated to reach 160 mm while the peak EPWP value can reach 26.55 kPa.The settlement discrepancies between the numerical method and empirical method are discussed in detail.
基金supported by the Science and Technology Commission of Shanghai Municipality(Grant No.18DZ1205902)the Key innovation team program of innovation talents promotion plan by MOST of China(No.2016RA4059)the National Key R&D Program of China(Grant No.2018YFB2101000).
文摘Metro tunnels play a crucial role in urban transportation.However,with growing tunnel operation periods,defects,and large deformations appearing,these are influencing tunnel structural performance and threatening public safety.Three-dimensional(3D)tunnel reconstruction is an effective way to highlight tunnel conditions and provide a basis for engineering management and maintenance.However,the current methods of tunnel 3D reconstruction do not sufficiently combine the qualitative and quantitative characteristics of tunnel states.In this study,a novel method for metro tunnel 3D reconstruction based on structure from motion(SfM)and direct linear transformation(DLT)is proposed.The dimensionless 3D reconstruction point cloud acquired through the SfM method showcases the qualitative characteristics(such as leakage and pipelines)of the tunnel state.The close-range photogrammetry DLT method provides scale information missing from the SfM method and quantitative characteristics(such as profile deformation)of the tunnel state.The SfM-DLT method was tested in a Shanghai metro tunnel,and proved to be feasible and promising for future tunnel inspections.
基金National Natural Science Foundation of China (Grant No.52178393)the Science and Technology Innovation Team of Shaanxi Innovation Capability Support Plan (Grant No.2020TD005)Science and Technology Innovation Project of China Railway Construction Bridge Engineering Bureau Group Co.,Ltd.(Grant No.DQJ-2020-B07)。
文摘Evaluating the adaptability of cantilever boring machine(CBM) through in-depth excavation and analysis of tunnel excavation data and rock mass parameters is the premise of mechanical design and efficient excavation in the field of underground space engineering.This paper presented a case study of tunnelling performance prediction method of CBM in sedimentary hard-rock tunnel of Karst landform type by using tunneling data and surrounding rock parameters.The uniaxial compressive strength(UCS),rock integrity factor(Kv),basic quality index([BQ]),rock quality index RQD,brazilian tensile strength(BTS) and brittleness index(BI) were introduced to construct a performance prediction database based on the hard-rock tunnel of Guiyang Metro Line 1 and Line 3,and then established the performance prediction model of cantilever boring machine.Then the deep belief network(DBN) was introduced into the performance prediction model,and the reliability of performance prediction model was verified by combining with engineering data.The study showed that the influence degree of surrounding rock parameters on the tunneling performance of the cantilever boring machine is UCS > [BQ] > BTS >RQD > Kv > BI.The performance prediction model shows that the instantaneous cutting rate(ICR) has a good correlation with the surrounding rock parameters,and the predicting model accuracy is related to the reliability of construction data.The prediction of limestone and dolomite sections of Line 3 based on the DBN performance prediction model shows that the measured ICR and predicted ICR is consistent and the built performance prediction model is reliable.The research results have theoretical reference significance for the applicability analysis and mechanical selection of cantilever boring machine for hard rock tunnel.
基金supported by the Key Field Science and Technology Project of Yunnan Province(Grant No.202002AC080002)the National Natural-Science Foundation of China(Grant No.52078377).
文摘Various structural defects deteriorate tunnel operation status and threaten public safety.Current tunnel inspection methods face problems of low efficiency,high equipment expense,and difficult data management.Combining the deep learning model and the 3D reconstruction method based on structure from motion(SfM),this paper proposes a novel SfM-Deep learning method for tunnel inspection.The high-quality 3D tunnel model is constructed by using images taken every 1 m along the longitudinal direction.The instance segmentation of leakage in longitudinal images is realized using the mask region-based convolutional neural network deep learning model.The SfM-Deep learning method projects the texture of the images after defect recognition to the 3D model and realizes the visualization of leakage defects.By projecting the model to the design cylindrical surface and expanding it,the tunnel leakage area is quantified.Through its practical application in a Shanghai metro shield tunnel,the reliability of the proposed method was verified.The novel SfM-Deep learning method can help engineers efficiently carry out intelligent tunnel detection.
基金Beijing Science and Technology Planning Project(No.D0604003040921)
文摘Constructing a metro station by enlarging shield tunnels combined with a mining/cut-and-cover method provides a new method to solve the contradictions of construction time limits of shield tunnels and stations. As a new-style construction method, there are several specific risks involved in the construction process. Based on the test section of Sanyuanqiao station on Beijing metro line 10, and combined with the existing methods of risk identification at present, including a review of world-wide operational experience of similar projects, the study of generic guidance on hazards associated with the type of work being undertaken, and discussions with qualified and experienced staff from the project team, etc., the specific risks during the construction process of the metro station constructed by enlarging shield tunnels combined with the cut-and-cover method are identified. The results show that the specific risks mainly come from three construction processes which include constructing upper enclosure structures, excavating the soil between shield tunnels and demolishing shield segments. Then relevant risk mitigation measures are put forward. The results can provide references for scheme improvement and a comprehensive risk assessment of the new-style construction method.
