Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugatio...Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.展开更多
Metro systems are important transport infrastructures in megacities,and their long-term operational safety is challenged by frequent external disturbances,such as environmental extremes and human construction activ-it...Metro systems are important transport infrastructures in megacities,and their long-term operational safety is challenged by frequent external disturbances,such as environmental extremes and human construction activ-ities.A metro system must be resilient to resist,adapt to,and recover its performance when such disruptions occur.Current studies on metro system resilience often lack a comprehensive view from a complex system perspective,leading to a plethora of choices for methods of analysis and indicators applied to different metro systems and external disturbances.Therefore,the present paper aims to provide a comprehensive review of the topics and works revolving around the resilience of metro systems.It first clarifies the concept of metro system resilience based on classical definitions from a technical perspective.Metro resilience encompasses both the structural and operational aspects of metro systems,including their damage mechanisms,analysis methods and indicators of resilience.Methods for enhancing metro system resilience across structural,operational and monitoring dimensions are explored.Finally,future research directions are discussed,emphasizing the impor-tance of considering the"system of systems"formed by interdependent infrastructure,refining uncertainty analysis,and investigating the opportunities arising from the application of artificial intelligence for improving metro system resilience against external disturbances.展开更多
This study offers valuable insights into the relationship between metro ridership patterns and the spatial transformations around Delhi Metro stations,underscoring the role of mass transit infrastructure in shaping ur...This study offers valuable insights into the relationship between metro ridership patterns and the spatial transformations around Delhi Metro stations,underscoring the role of mass transit infrastructure in shaping urban land use and ecosystem landscapes.The primary objective is to assess how high-ridership metro stations can positively influence urban development,particularly regarding socio-economic and ecological dimensions.Integrating primary survey data with ridership statistics from the Delhi Metro Rail Corporation(DMRC),the research identifies key interchange stations,such as Kashmere Gate and Rajiv Chowk,which exhibit substantial passenger volumes.Utilising GIS-based spatial analysis and remote sensing techniques,land use changes within a 500-meter buffer zone around these stations are considered,focusing on built-up areas,green cover,and open space availability.Time-series satellite imagery generates comparative maps illustrating land use changes pre-and post-introduction of metro services.The analysis reveals that high-ridership stations are linked to significant commercial densification,particularly near Rajiv Chowk,with a p-value of 0.172.Conversely,peripheral stations like Dwarka Sector 21 indicate residential growth trends,with a p-value of 0.087 for residential areas.Importantly,two land use categories—Green Space(t=-2.33,p=0.045)and Open Space(t=3.57,p=0.006)—show statistically significant reductions,highlighting the ecological impacts of metro infrastructure.The findings suggest that metro systems can promote commercial clustering in urban centres while fostering residential growth in surrounding areas.Overall,the study highlights the potential of metro systems to enhance accessibility,reshape urban ecosystems,and encourage the development of compact urban forms.The implications for urban planning advocate for transit-oriented development(TOD)as a strategic approach to manage growth,minimise sprawl,and ensure sustainable and inclusive development.展开更多
As a key mode of transportation, urban metro networks have significantly enhanced urban traffic environments and travel efficiency, making the identification of critical stations within these networks increasingly ess...As a key mode of transportation, urban metro networks have significantly enhanced urban traffic environments and travel efficiency, making the identification of critical stations within these networks increasingly essential. This study presents a novel integrated topological-functional(ITF) algorithm for identifying critical nodes, combining topological metrics such as K-shell decomposition, node information entropy, and neighbor overlapping interaction with the functional attributes of passenger flow operations, while also considering the coupling effects between metro and bus networks. Using the Chengdu metro network as a case study, the effectiveness of the algorithm under different conditions is validated.The results indicate significant differences in passenger flow patterns between working and non-working days, leading to varying sets of critical nodes across these scenarios. Moreover, the ITF algorithm demonstrates a marked improvement in the accuracy of critical node identification compared to existing methods. This conclusion is supported by the analysis of changes in the overall network structure and relative global operational efficiency following targeted attacks on the identified critical nodes. The findings provide valuable insight into urban transportation planning, offering theoretical and practical guidance for improving metro network safety and resilience.展开更多
With the increasing adoption of intelligent operation and maintenance technologies in urban rail transit,most maintenance systems have been equipped with fault diagnosis modules targeting key components of metro vehic...With the increasing adoption of intelligent operation and maintenance technologies in urban rail transit,most maintenance systems have been equipped with fault diagnosis modules targeting key components of metro vehicles.However,the integration between engineering-level diagnostic algorithms and advanced academic research remains limited.Two major challenges hinder vibration-based fault diagnosis under real-world operating conditions:the complex noise and interference caused by wheel-rail coupling and the typically weak expression of fault features.Considering the widespread application of wavelet transform in noise reduction and the maturity of ensemble empirical mode decomposition(EEMD)in handling nonlinear and non-stationary signals without parameter tuning,this study proposes a diagnostic method that combines wavelet threshold denoising with EEMD.The method was applied to bearing vibration signals collected from an operational subway line.The diagnostic results were consistent with actual disassembly findings,demonstrating the effectiveness and practical value of the proposed approach.展开更多
Metro is an important form of public transport in Shanghai.Based on the metro card data,we conduct the cluster analysis of Shanghai metro stations according to the pattern of passenger flow changing with time.Then the...Metro is an important form of public transport in Shanghai.Based on the metro card data,we conduct the cluster analysis of Shanghai metro stations according to the pattern of passenger flow changing with time.Then the characteristics of travel time and surrounding land use are investigated for different types of stations to explore the relationship between urban land-use characteristics and travel activities reflected by passenger flow at metro stations.It is found that the passenger flow pattern of metro stations is closely related to the location conditions of stations and its surrounding land-use patterns.Based on various characteristics,285 metro stations are classified into four types,including residential-oriented stations,employmentoriented stations,employment-residence-oriented stations,and integrated functionaloriented stations,reflecting the interaction between spontaneous travel behavior and urban land-use characteristics and providing a reference for optimizing the urban functional structure and the spatial allocation of facilities.展开更多
The metro is the most efficient and convenient public transport system in modern cities. For urban core areas in China, in which the metro was built later, there was more consideration for meeting the traffic needs of...The metro is the most efficient and convenient public transport system in modern cities. For urban core areas in China, in which the metro was built later, there was more consideration for meeting the traffic needs of cities. However, there are few studies of collaborative planning for metro stations and their surrounding space. Thus, there is an urgent need to conduct research on collaborative planning for metro stations and their surrounding commercial space in urban core areas. Unlike conventional methods of integrated design of stations and cities, this paper, based on the theory of place spirit, took Chunxi Road Metro Station in Chengdu and its surrounding commercial space for example. It explored the pattern and characteristics of the place in the commercial space around the metro station, analyzed the strategies of cultural and commercial integration, as well as architecture, street, landscape and other aspects of the design method in the space, and explored the strategies of place-making and infiltration, providing a reference point for the development and place-making of the commercial space around metro stations in urban core areas.展开更多
This study explores the factors influencing metro passengers’ arrival volume in Wuhan, China, and Lagos, Nigeria, by examining weather, time of day, waiting time, travel behavior, arrival patterns, and metro satisfac...This study explores the factors influencing metro passengers’ arrival volume in Wuhan, China, and Lagos, Nigeria, by examining weather, time of day, waiting time, travel behavior, arrival patterns, and metro satisfaction. It addresses a significant research gap in understanding metro passengers’ dynamics across cultural and geographical contexts. It employs questionnaires, field observations, and advanced data analysis techniques like association rule mining and neural network modeling. Key findings include a correlation between rainy weather, shorter waiting times, and higher arrival volumes. Neural network models showed high predictive accuracy, with waiting time, metro satisfaction, and weather being significant factors in Lagos Light Rail Blue Line Metro. In contrast, arrival patterns, weather, and time of day were more influential in Wuhan Metro Line 5. Results suggest that improving metro satisfaction and reducing waiting times could increase arrival volumes in Lagos Metro while adjusting schedules for weather and peak times could optimize flow in Wuhan Metro. These insights are valuable for transportation planning, passenger arrival volume management, and enhancing user experiences, potentially benefiting urban transportation sustainability and development goals.展开更多
The land subsidence characteristics in Shanghai were constantly developing with the change of groundwater level in the process of urban development,and had different effects on the deformation of metro tunnels buried ...The land subsidence characteristics in Shanghai were constantly developing with the change of groundwater level in the process of urban development,and had different effects on the deformation of metro tunnels buried in deep soft soil layers.In this study,the long time series field monitoring data obtained by levelling and stratification extensometer methods was analyzed,and the coupling deformation mechanism of geological stratification and metro tunnel in deep quaternary coastal areas for different periods and scenarios was revealed.The results showed that with the rapid rise of the groundwater level in Shanghai since 2005,the deep sedimentary strata gradually rebound,resulting in the universal rebound of underground metro tunnel.The deformation trends of soil layers and metro tunnel structure were inconsistent with the regional land subsidence due to different control factors.For metro lines built in different periods,the tunnel displacement was basically controlled by the deformation of sedimentary strata below the tunnel structure.The coupling deformation of geological stratification and metro tunnel structure in the deep Quaternary sedimentary area can be described in three conceptual calculation models:inverse settlement model,extrusion model and counteract model.The hysteresis effects when the increase of water volume transformed to the rise of groundwater level and the soil layer deformation driven by rising water level were discussed.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
The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehi...The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.展开更多
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
基金support extended by the Joint Funds of Beijing Municipal Natural Science Foundation and Fengtai Rail Transit Frontier Research(Grant No.L211006)the Fundamental Research Funds for the Central Universities(Science and technology leading talent team project,Grant No.2022JBXT010)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.2023YJS052)the National Natural Science Foundation of China(Grant No.52308426)。
文摘Investigations into rail corrugation within metro systems have traditionally focused on specific mechanisms,thereby limiting the generalizability of proposed theories.Understanding the commonalities in rail corrugation across diverse metro lines remains pivotal for elucidating its underlying mechanisms.The present study conducted extensive field surveys and tracking tests across 14 Chinese metro lines.By employing t-distributed stochastic neighbor embedding(t-SNE)for dimensional reduction and employing the unsupervised clustering algorithm DBSCAN,the research redefines the classification of metro rail corrugation based on characteristic information.The analysis encompassed spatial distribution and temporal evolution of this phenomenon.Findings revealed that floating slab tracks exhibited the highest proportion of rail corrugation at 47%.Notably,ordinary monolithic bed tracks employing damping fasteners were more prone to inducing rail corrugation.Corrugation primarily manifested in curve sections with radii between 300 and 500 m,featuring ordinary monolithic bed track and steel-spring floating slab track structures,with wavelengths typically between 30 and 120 mm.Stick–slip vibrations of the wheel–rail system maybe led to short-wavelength corrugations(40–60 mm),while longer wavelengths(200–300 mm)exhibited distinct fatigue damage characteristics,mainly observed in steel-spring floating slab tracks and small-radius curve sections of ordinary monolithic bed tracks and ladder sleeper tracks.A classification system comprising 57 correlated features categorized metro rail corrugation into four distinct types.These research outcomes serve as critical benchmarks for validating various theories pertaining to rail corrugation formation.
基金supported by National Key R&D Program of China 2024YFC3808804National Natural Science Foundation of China NO.52478411+1 种基金China Scholarship Council No.202506260003Jinan Rail Transit Group Co.,Ltd(ggjn-sd-gd2022008fw).
文摘Metro systems are important transport infrastructures in megacities,and their long-term operational safety is challenged by frequent external disturbances,such as environmental extremes and human construction activ-ities.A metro system must be resilient to resist,adapt to,and recover its performance when such disruptions occur.Current studies on metro system resilience often lack a comprehensive view from a complex system perspective,leading to a plethora of choices for methods of analysis and indicators applied to different metro systems and external disturbances.Therefore,the present paper aims to provide a comprehensive review of the topics and works revolving around the resilience of metro systems.It first clarifies the concept of metro system resilience based on classical definitions from a technical perspective.Metro resilience encompasses both the structural and operational aspects of metro systems,including their damage mechanisms,analysis methods and indicators of resilience.Methods for enhancing metro system resilience across structural,operational and monitoring dimensions are explored.Finally,future research directions are discussed,emphasizing the impor-tance of considering the"system of systems"formed by interdependent infrastructure,refining uncertainty analysis,and investigating the opportunities arising from the application of artificial intelligence for improving metro system resilience against external disturbances.
基金funded by the Institution of Eminence,with the University of Delhi cited as IoE/2024-25/12/FRP.
文摘This study offers valuable insights into the relationship between metro ridership patterns and the spatial transformations around Delhi Metro stations,underscoring the role of mass transit infrastructure in shaping urban land use and ecosystem landscapes.The primary objective is to assess how high-ridership metro stations can positively influence urban development,particularly regarding socio-economic and ecological dimensions.Integrating primary survey data with ridership statistics from the Delhi Metro Rail Corporation(DMRC),the research identifies key interchange stations,such as Kashmere Gate and Rajiv Chowk,which exhibit substantial passenger volumes.Utilising GIS-based spatial analysis and remote sensing techniques,land use changes within a 500-meter buffer zone around these stations are considered,focusing on built-up areas,green cover,and open space availability.Time-series satellite imagery generates comparative maps illustrating land use changes pre-and post-introduction of metro services.The analysis reveals that high-ridership stations are linked to significant commercial densification,particularly near Rajiv Chowk,with a p-value of 0.172.Conversely,peripheral stations like Dwarka Sector 21 indicate residential growth trends,with a p-value of 0.087 for residential areas.Importantly,two land use categories—Green Space(t=-2.33,p=0.045)and Open Space(t=3.57,p=0.006)—show statistically significant reductions,highlighting the ecological impacts of metro infrastructure.The findings suggest that metro systems can promote commercial clustering in urban centres while fostering residential growth in surrounding areas.Overall,the study highlights the potential of metro systems to enhance accessibility,reshape urban ecosystems,and encourage the development of compact urban forms.The implications for urban planning advocate for transit-oriented development(TOD)as a strategic approach to manage growth,minimise sprawl,and ensure sustainable and inclusive development.
基金Project supported by the National Natural Science Foundation of China (Grant No. 71971150)the Project of Research Center for System Sciences and Enterprise Development (Grant No. Xq16B05)the Fundamental Research Funds for the Central Universities of China (Grant No. SXYPY202313)。
文摘As a key mode of transportation, urban metro networks have significantly enhanced urban traffic environments and travel efficiency, making the identification of critical stations within these networks increasingly essential. This study presents a novel integrated topological-functional(ITF) algorithm for identifying critical nodes, combining topological metrics such as K-shell decomposition, node information entropy, and neighbor overlapping interaction with the functional attributes of passenger flow operations, while also considering the coupling effects between metro and bus networks. Using the Chengdu metro network as a case study, the effectiveness of the algorithm under different conditions is validated.The results indicate significant differences in passenger flow patterns between working and non-working days, leading to varying sets of critical nodes across these scenarios. Moreover, the ITF algorithm demonstrates a marked improvement in the accuracy of critical node identification compared to existing methods. This conclusion is supported by the analysis of changes in the overall network structure and relative global operational efficiency following targeted attacks on the identified critical nodes. The findings provide valuable insight into urban transportation planning, offering theoretical and practical guidance for improving metro network safety and resilience.
文摘With the increasing adoption of intelligent operation and maintenance technologies in urban rail transit,most maintenance systems have been equipped with fault diagnosis modules targeting key components of metro vehicles.However,the integration between engineering-level diagnostic algorithms and advanced academic research remains limited.Two major challenges hinder vibration-based fault diagnosis under real-world operating conditions:the complex noise and interference caused by wheel-rail coupling and the typically weak expression of fault features.Considering the widespread application of wavelet transform in noise reduction and the maturity of ensemble empirical mode decomposition(EEMD)in handling nonlinear and non-stationary signals without parameter tuning,this study proposes a diagnostic method that combines wavelet threshold denoising with EEMD.The method was applied to bearing vibration signals collected from an operational subway line.The diagnostic results were consistent with actual disassembly findings,demonstrating the effectiveness and practical value of the proposed approach.
文摘Metro is an important form of public transport in Shanghai.Based on the metro card data,we conduct the cluster analysis of Shanghai metro stations according to the pattern of passenger flow changing with time.Then the characteristics of travel time and surrounding land use are investigated for different types of stations to explore the relationship between urban land-use characteristics and travel activities reflected by passenger flow at metro stations.It is found that the passenger flow pattern of metro stations is closely related to the location conditions of stations and its surrounding land-use patterns.Based on various characteristics,285 metro stations are classified into four types,including residential-oriented stations,employmentoriented stations,employment-residence-oriented stations,and integrated functionaloriented stations,reflecting the interaction between spontaneous travel behavior and urban land-use characteristics and providing a reference for optimizing the urban functional structure and the spatial allocation of facilities.
基金Sponsored by Technology Research Program of Sichuan Province of China(2016JY0111)
文摘The metro is the most efficient and convenient public transport system in modern cities. For urban core areas in China, in which the metro was built later, there was more consideration for meeting the traffic needs of cities. However, there are few studies of collaborative planning for metro stations and their surrounding space. Thus, there is an urgent need to conduct research on collaborative planning for metro stations and their surrounding commercial space in urban core areas. Unlike conventional methods of integrated design of stations and cities, this paper, based on the theory of place spirit, took Chunxi Road Metro Station in Chengdu and its surrounding commercial space for example. It explored the pattern and characteristics of the place in the commercial space around the metro station, analyzed the strategies of cultural and commercial integration, as well as architecture, street, landscape and other aspects of the design method in the space, and explored the strategies of place-making and infiltration, providing a reference point for the development and place-making of the commercial space around metro stations in urban core areas.
文摘This study explores the factors influencing metro passengers’ arrival volume in Wuhan, China, and Lagos, Nigeria, by examining weather, time of day, waiting time, travel behavior, arrival patterns, and metro satisfaction. It addresses a significant research gap in understanding metro passengers’ dynamics across cultural and geographical contexts. It employs questionnaires, field observations, and advanced data analysis techniques like association rule mining and neural network modeling. Key findings include a correlation between rainy weather, shorter waiting times, and higher arrival volumes. Neural network models showed high predictive accuracy, with waiting time, metro satisfaction, and weather being significant factors in Lagos Light Rail Blue Line Metro. In contrast, arrival patterns, weather, and time of day were more influential in Wuhan Metro Line 5. Results suggest that improving metro satisfaction and reducing waiting times could increase arrival volumes in Lagos Metro while adjusting schedules for weather and peak times could optimize flow in Wuhan Metro. These insights are valuable for transportation planning, passenger arrival volume management, and enhancing user experiences, potentially benefiting urban transportation sustainability and development goals.
基金financial support provided by the Science and Technology Commission of Shanghai Municipality(grant no.22ZR1447100,21DZ1204200 and 23XD1402400).
文摘The land subsidence characteristics in Shanghai were constantly developing with the change of groundwater level in the process of urban development,and had different effects on the deformation of metro tunnels buried in deep soft soil layers.In this study,the long time series field monitoring data obtained by levelling and stratification extensometer methods was analyzed,and the coupling deformation mechanism of geological stratification and metro tunnel in deep quaternary coastal areas for different periods and scenarios was revealed.The results showed that with the rapid rise of the groundwater level in Shanghai since 2005,the deep sedimentary strata gradually rebound,resulting in the universal rebound of underground metro tunnel.The deformation trends of soil layers and metro tunnel structure were inconsistent with the regional land subsidence due to different control factors.For metro lines built in different periods,the tunnel displacement was basically controlled by the deformation of sedimentary strata below the tunnel structure.The coupling deformation of geological stratification and metro tunnel structure in the deep Quaternary sedimentary area can be described in three conceptual calculation models:inverse settlement model,extrusion model and counteract model.The hysteresis effects when the increase of water volume transformed to the rise of groundwater level and the soil layer deformation driven by rising water level were discussed.
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.
基金Supported by National Natural Science Foundation of China(Grant Nos.U1361117,51305360)PhD Programs Foundation of Ministry of Education of China(Grant No.20130184110005)+1 种基金Cultivation Program for the Excellent Doctoral Dissertation of Southwest Jiaotong UniversityGuangzhou Metro Corporation Program of China
文摘The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.
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.
