In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When...In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.展开更多
Background:Recent literature indicates that the pollutant,particulate matter PM2.5,may have an impact on COVID-19 related infection and mortality.Genes coding for SARS-CoV-2 has been found adherent to PM2.5 and possib...Background:Recent literature indicates that the pollutant,particulate matter PM2.5,may have an impact on COVID-19 related infection and mortality.Genes coding for SARS-CoV-2 has been found adherent to PM2.5 and possibly the COVID-19/PM2.5 complex may be involved in the transmission and the exacerbation of COVID-19 infection.PM2.5 levels in deep underground subways have been found up to 90 times higher than roads closer to the surface.Method:The levels of PM2.5 were retrieved from literature assessing particulate matter PM2.5 measured on subway platforms in two groups of cities.These cities were differentiated by the COVID-19 population percentage mortality rate(0.007%vs 0.19%)(P<0.0004).Data regarding the number of stations,length of the networks(km)and the annual ridership were also obtained from literature related to underground commuting.Results:The population percentage mortality related to SARS-CoV-2 infection correlated significantly for both minimum(P<0.01)and maximum(P<0.00001)levels of PM2.5.The cities’subways with low COVID-19 mortality had minimum platform PM2.5 levels of 27.4(SD+/-17.2μg/m3)compared to 63.4μg/m3(SD+/-10.8μg/m3)in cities with high SARS-CoV-2 associated mortality(P<0.01).Subway maximum levels of PM2.5 in cities with low COVID-19 mortality was 53.4μg/m3(SD+/-21.8μg/m3)while that of underground networks with high COVID-19 mortality had maximum platform PM2.5 levels of 172.1μg/m3(SD+/-98μg/m3)(P<0.001).Conclusion:Underground networks may have inherent characteristics accelerating spread of SARSCoV-2 infection and consequent mortality.The highly elevated levels of PM2.5 in overcrowded subways with extensive reach,may have acted as a co-factor to disseminate the pandemic in a number of metropolises.展开更多
This paper aims to examine the role of the subway network,a typical form of transportation within urban areas,on innovation and knowledge diffusion.Applying the differece-in-diferences strategy and spatial analysis,we...This paper aims to examine the role of the subway network,a typical form of transportation within urban areas,on innovation and knowledge diffusion.Applying the differece-in-diferences strategy and spatial analysis,we used 1,332 newly opened stations in China from 2000 to 2013 as a quasi-experiment to identify the local effects of subway expansions.Results suggested that by reducing communication costs and increasing opportunities for interaction,subway construction would bring growth at the district level.Knowledge dissemination would become more active after new stations open.Micro-level results showed that these positive impacts were highly localized;that is,only those firms located within lkm around stations benefited from the new subway.Moreover,new subways facilitated the flow of knowledge from station to station and assisted.firms in acquiring knowledge from more distant technology clusters conveniently.展开更多
The tall trees in Nanjing,capital city of east China’s Jiangsu Province,are an amenity local people boast about.In1928,in order to commemorate Sun Yat-sen,founder o the Kuomintang,hundreds
Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynami...Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynamics of pedestrian counterflow at bottlenecks, utilizing subway passenger alighting and boarding as a case study. Specifically, the efficiency and safety of three distinct movement modes: the cooperative mode(Coop), the combination of cooperative and competitive mode(C & C), and the competitive mode(Comp), were examined and compared. The experimental findings revealed that the C & C mode exhibited a clear lane formation phenomenon and demonstrated a higher flow rate than the Comp and Coop modes. This observation suggests that a combination of cooperative and competitive behaviors among pedestrians can positively enhance traffic efficiency and safety during the alighting and boarding process. In contrast, pedestrians exhibited increased detouring in their paths and more fluctuating trajectories in the Comp mode. Additionally, a questionnaire survey assessing the level of competition and cooperation among pedestrians provided a comprehensive analysis of the psychological dynamics of passengers during the alighting and boarding activities. Lastly, the proposed force-based model was calibrated and validated, demonstrating a good performance in accurately replicating the overall characteristics of the experimental process. Overall, this study offers valuable insights into enhancing the pedestrian traffic efficiency and safety within subway systems.展开更多
The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with...The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with a hard combination,a numerical model is developed in this study.The indoor model test verified the accuracy of the numerical model.The influence laws of different hard combinations,train operating speeds and modes were studied and evaluated accordingly.The results show that the frequency corresponding to the peak vibration acceleration level of each floor of the superstructure property is concentrated at 10–20 Hz.The vibration response decreases in the high-frequency parts and increases in the lowfrequency parts with increasing distance from the source.Furthermore,the factors,such as train operating speed,operating mode,and hard combination type,will affect the vibration of the superstructure.The vibration response under the reversible operation of the train is greater than that of the unidirectional operation.The operating speed of the train is proportional to its vibration response.The vibration amplification area appears between the middle and the top of the superstructure at a higher train speed.Its vibration acceleration level will exceed the limit value of relevant regulations,and vibration-damping measures are required.Within the scope of application,this study provides some suggestions for constructing subway stations and superstructures.展开更多
The Hongyancun subway station in Chongqing,China,is 116 meters deep and the difference in air pressure often leaves users with clogged(堵塞的)ears when accessed via its elevator.When the air pressure outside the eardr...The Hongyancun subway station in Chongqing,China,is 116 meters deep and the difference in air pressure often leaves users with clogged(堵塞的)ears when accessed via its elevator.When the air pressure outside the eardrum(耳膜)becomes different than the pressure inside,you experience ear barotrauma(气压伤).It occurs most often during steep ascents and descents and is usually associated with plane take⁃offs and landings,or driving up or down mountains.Most subway stations dont usually cause ear barotrauma,because they arent deep or steep enough for your ears to register a significant enough difference in air pressure.But taking the elevator to reach Chinas deepest subway station might actually clog up your ears.Thats because it is located 116 meters below the surface,which is the equivalent of about 40 floors underground.展开更多
Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissur...Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissure area was developed and validated by using experimental results.Numerical analyses were conducted to investigate the seismic response and failure mode of subway stations in a ground fissure area with different locations.Effects of ground fissure on deformations and internal forces of a station,soil pressures and soil plastic strains were discussed.The results showed that the seismic response of the station was significantly amplified by the ground fissure,and stations in the ground fissure area displayed obvious rocking deformation during earthquakes as compared to those in the area without fissures.It also was found that the soil yielding around the station,the dislocation occurring in the ground fissure area,and the dynamic amplification effect were more significant under vertical ground motion,which weakened the station’s ductility and accelerated its destruction process.展开更多
This study examines the variations in noise levels across various subway lines in Singapore and three other cities,and provides a detailed overview of the trends and factors influencing subway noise.Most of the equiva...This study examines the variations in noise levels across various subway lines in Singapore and three other cities,and provides a detailed overview of the trends and factors influencing subway noise.Most of the equivalent sound pressure level(Leq)in typical subway cabins across the Singapore subway lines are below 85 dBA,with some notable exceptions.These variations in noise levels are influenced by several factors,including rolling stock structure,track conditions and environmental and aerodynamic factors.The spectrogram analysis indicates that the cabin noise is mostly concentrated below the frequency of 1,000 Hz.This study also analyzes cabin noise in subway systems in Suzhou,Seoul,and Tokyo to allow for broader comparisons.It studies the impact of factors such as stock materials,track conditions including the quality of the rails,the presence of curves or irregularities,and maintenance frequency on cabin noise.展开更多
Based on the distribution of cooling load at a subway station and the peak-valley electricity price in Guangzhou,a chilled water storage system is reserved in the ample space above the station's distribution area....Based on the distribution of cooling load at a subway station and the peak-valley electricity price in Guangzhou,a chilled water storage system is reserved in the ample space above the station's distribution area.This study proposes a design scheme and operational strategy for a chilled water storage system suitable for subway engineering,based on calculating the cooling load and designing a chilled water storage system in a subway station.Additionally,it proposes calculation coefficients of hourly cooling load suitable for subway engineering and convenient for estimation of hourly cooling load.Furthermore,an economic analysis is conducted by combining hourly cooling load with time-of-use electricity prices.This study provides a reference for the design and application of chilled water storage systems in subsequent subway projects.展开更多
To explore the influence of emergency evacuation signs on passenger behavior during subway fires and improve evacuation efficiency in emergencies,this paper proposes a dynamic emergency evacuation sign system.A simula...To explore the influence of emergency evacuation signs on passenger behavior during subway fires and improve evacuation efficiency in emergencies,this paper proposes a dynamic emergency evacuation sign system.A simulation platform integrating building information modeling(BIM)and virtual reality(VR)technologies was em-ployed to create subway fire evacuation scenarios using both the current and proposed dynamic emergency evacuation signage systems.Through simulation experiments,fine-grained microscopic data on passenger behavior was collected.Seven indicators were selected to assess evacuation efficiency and wayfinding difficulty.The analysis explored the influence of evacuation signs on passenger behavior in both overall and decision-making areas,thereby validating the effectiveness of the new emergency evacuation signage system.The results show that the dynamic evacuation signage system significantly improves overall passenger evacuation efficiency and reduces decision-making errors.It also improves wayfinding efficiency in critical decision areas by reducing the need for direction identification,minimizing stopping times,and lowering the frequency of decision errors.The method for evaluating the effects of emergency evacuation signs on passenger evacuation behavior proposed in this study provides a robust theoretical basis for the design and optimization of emergency-oriented signs.展开更多
In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental ...In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental magnetic field noise in the vicinity of Beijing Subway Line 4 using a three-component height Tc radio frequency （rf） superconducting quantum interference device （SQUID）. By analysing the spatial form and other characteristics of the time and the fre- quency domains and by calculating the circumferential magnetic field distribution based on a duel-end feeding system model, we reach the following conclusions： （i） the main source of magnetic field noise is the magnetic field generated by thel subway trains, and （ii） the magnetic field interference results mainly from the imbalance between traction current and return rail current that is caused by the leakage current.展开更多
In rebuilding Tianjin Metro, numerical simulations are performed to evaluate the original design of the ventilation system of Southwest Station and a new system is given to optimize the velocity and temperature fields...In rebuilding Tianjin Metro, numerical simulations are performed to evaluate the original design of the ventilation system of Southwest Station and a new system is given to optimize the velocity and temperature fields at the station. Field measurements are conducted to validate the turbulence model and acquire boundary conditions. The simulation result tallies with testing data on the sport that is found that two-equation turbulence model is acceptable in simulating complex flow at the station. A method of simplifying the simulation of the transient flow at the station into steady flow is used and the validation criterion for this simulation is also given.展开更多
The internal flow field study of car compartments is an important step in railroad vehicle design and optimization. The flow field profile has a significant impact on the temperature distribution and passenger comfort...The internal flow field study of car compartments is an important step in railroad vehicle design and optimization. The flow field profile has a significant impact on the temperature distribution and passenger comfort level. Experimental studies on flow field can yield accurate results but carry a high time and computational cost. In contrast, the numerical simulation method can yield an internal flow field profile in less time than an experimental study. This study aims to improve the computational efficiency of numerical simulation by adapting two simplified models—the porous media model and the porous jump face model—to study the internal flow field of a railroad car compartment. The results provided by both simplified models are compared with the original numerical simulation model and with experimental data. Based on the results, the porous media model has a better agreement with the original model and with the experimental results. The flow field parameters (temperature and velocity) of the porous media model have relatively small numerical errors, with a maximum numerical error of 4.7%. The difference between the numerical results of the original model and those of the porous media model is less than 1%. By replacing the original numerical simulation model with the porous media model, the flow field of subway car compartments can be calculated with a reduction of about 25% in computing resources, while maintaining good accuracy.展开更多
Construction of metro tunnels in dense and crowded urban areas is faced with many risks, such as sub- sidence. The purpose of this paper was the prediction of subsidence risk by failure mode and effect anal- ysis （F...Construction of metro tunnels in dense and crowded urban areas is faced with many risks, such as sub- sidence. The purpose of this paper was the prediction of subsidence risk by failure mode and effect anal- ysis （FMEA） and fuzzy inference system （FIS）. Fuzzy theory will be able to model uncertainties. Fuzzy FMEA provides a tool that can work in a better way with vague concepts and without sufficient informa- tion than conventional FMEA. In this paper, S and D are obtained from fuzzy rules and 0 is obtained from artificial neural network （ANN）. FMEA is performed by developing a fuzzy risk priority number （FRPN）. The FRPN for two stations in Tehran No.4 subway line is 3.1 and 5.5, respectively. To investigate the suit- ability of this approach, the predictions by FMEA have been compared with actual data. The results show that this method can be useful in the prediction of subsidence risk in urban tunnels.展开更多
Background:Since the 1970 s,terrorist bombings in subways have been frequently occurring worldwide.To cope with this threat and to provide medical response countermeasures,we analyzed the characteristics of subway bom...Background:Since the 1970 s,terrorist bombings in subways have been frequently occurring worldwide.To cope with this threat and to provide medical response countermeasures,we analyzed the characteristics of subway bombing terrorist attacks and used the Haddon matrix to explore medical response strategies.Methods:First,we analyzed 111 subway bombings from 1970 to 2017 recorded in the Global Terrorism Database to provide a reference for the strategy exploration.Then,we convened an expert panel to use the Haddon matrix to explore the medical response strategies to subway bombings.Results:In recent decades,at least one bombing attack occurs every 3 years.Summarized by the Haddon matrix,the influencing factors of medical responses to conventional subway bombings include the adequacy of first-aid kits and the medical evacuation equipment,the traffic conditions affecting the evacuation,the continuity and stability of communication,as well as the factors exclusively attributed to dirty bomb attacks in subways,such as ionizing radiation protection capabilities,the structure of the radiation sickness treatment network based on the subway lines,and the disposal of radioactive sewage.These factors form the basis of the strategy discussion.Conclusions:Since subway bombings are long-term threats,it is necessary to have proper medical response preparation.Based on the Haddon matrix,we explored the medical response strategies for terrorist subway bombings,especially dirty bomb attacks.Haddon matrix can help policymakers systematically find the most important factors,which makes the preparations of the response more efficient.展开更多
In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,...In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,wave propagation in the infinitely extended ground is dealt with using a simple,yet efficient gradually damped artificial boundary.Based on the assumption of invariant geometry and material distribution in the tunnel's direction,the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number.Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number.The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform.The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum.A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.展开更多
There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment ...There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment services(e.g.,Internet,etc.) to passengers as well.The wireless channel in tunnels is quite unique due to the confined space and the waveguide effects.Therefore,modeling the radio channel characteristics in tunnels is critically important for communication systems design or optimization.This paper investigates the key radio channel characteristics of a subway tunnel at 2.4 GHz and 5 GHz,such as the path loss,root mean square(RMS) delay spread,channel stationarity,Doppler shift,and channel capacity.The field measurements show that channel characteristics in tunnels are highly location-dependent and there exist abundant components in Doppler shift domain.In the straight section of the subway tunnel,the measured path loss exponents are close to1.6,lower than that in free space.展开更多
Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical sol...Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical solution was discussed.The ground settlement width parameter which could reflect the ground condition was introduced to modify the analytical solutions proposed above,and new analytical solutions were presented.To evaluate the validity of the present solutions using the nonuniform convergence model,the results were compared with the observed values for four engineering projects,including 38 measured data of ground settlement.The agreement shows that the present solutions using the nonuniform convergence model are effective for evaluating the tunneling-induced ground displacements.展开更多
基金Projects BK2007145 supported by the Jiangsu Natural Science Foundation of China NCET-04-0454 by the Program for New Century Excellent Talentsin Universities
文摘In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.
文摘Background:Recent literature indicates that the pollutant,particulate matter PM2.5,may have an impact on COVID-19 related infection and mortality.Genes coding for SARS-CoV-2 has been found adherent to PM2.5 and possibly the COVID-19/PM2.5 complex may be involved in the transmission and the exacerbation of COVID-19 infection.PM2.5 levels in deep underground subways have been found up to 90 times higher than roads closer to the surface.Method:The levels of PM2.5 were retrieved from literature assessing particulate matter PM2.5 measured on subway platforms in two groups of cities.These cities were differentiated by the COVID-19 population percentage mortality rate(0.007%vs 0.19%)(P<0.0004).Data regarding the number of stations,length of the networks(km)and the annual ridership were also obtained from literature related to underground commuting.Results:The population percentage mortality related to SARS-CoV-2 infection correlated significantly for both minimum(P<0.01)and maximum(P<0.00001)levels of PM2.5.The cities’subways with low COVID-19 mortality had minimum platform PM2.5 levels of 27.4(SD+/-17.2μg/m3)compared to 63.4μg/m3(SD+/-10.8μg/m3)in cities with high SARS-CoV-2 associated mortality(P<0.01).Subway maximum levels of PM2.5 in cities with low COVID-19 mortality was 53.4μg/m3(SD+/-21.8μg/m3)while that of underground networks with high COVID-19 mortality had maximum platform PM2.5 levels of 172.1μg/m3(SD+/-98μg/m3)(P<0.001).Conclusion:Underground networks may have inherent characteristics accelerating spread of SARSCoV-2 infection and consequent mortality.The highly elevated levels of PM2.5 in overcrowded subways with extensive reach,may have acted as a co-factor to disseminate the pandemic in a number of metropolises.
文摘This paper aims to examine the role of the subway network,a typical form of transportation within urban areas,on innovation and knowledge diffusion.Applying the differece-in-diferences strategy and spatial analysis,we used 1,332 newly opened stations in China from 2000 to 2013 as a quasi-experiment to identify the local effects of subway expansions.Results suggested that by reducing communication costs and increasing opportunities for interaction,subway construction would bring growth at the district level.Knowledge dissemination would become more active after new stations open.Micro-level results showed that these positive impacts were highly localized;that is,only those firms located within lkm around stations benefited from the new subway.Moreover,new subways facilitated the flow of knowledge from station to station and assisted.firms in acquiring knowledge from more distant technology clusters conveniently.
文摘The tall trees in Nanjing,capital city of east China’s Jiangsu Province,are an amenity local people boast about.In1928,in order to commemorate Sun Yat-sen,founder o the Kuomintang,hundreds
基金Project supported by the National Natural Science Foundation of China (Grant No. 72301184)the Natural Science Foundation of Sichuan Province of China (Grant No. 2024NSFSC1073)the Fundamental Research Funds for the Central Universities (Grant No. YJ202329)。
文摘Efficiency and safety are paramount concerns for commuters, operators, and designers in subway stations. This study conducted controlled experiments and developed a modified force-based model to investigate the dynamics of pedestrian counterflow at bottlenecks, utilizing subway passenger alighting and boarding as a case study. Specifically, the efficiency and safety of three distinct movement modes: the cooperative mode(Coop), the combination of cooperative and competitive mode(C & C), and the competitive mode(Comp), were examined and compared. The experimental findings revealed that the C & C mode exhibited a clear lane formation phenomenon and demonstrated a higher flow rate than the Comp and Coop modes. This observation suggests that a combination of cooperative and competitive behaviors among pedestrians can positively enhance traffic efficiency and safety during the alighting and boarding process. In contrast, pedestrians exhibited increased detouring in their paths and more fluctuating trajectories in the Comp mode. Additionally, a questionnaire survey assessing the level of competition and cooperation among pedestrians provided a comprehensive analysis of the psychological dynamics of passengers during the alighting and boarding activities. Lastly, the proposed force-based model was calibrated and validated, demonstrating a good performance in accurately replicating the overall characteristics of the experimental process. Overall, this study offers valuable insights into enhancing the pedestrian traffic efficiency and safety within subway systems.
基金National Natural Science Foundation of China under Grant No.51578463。
文摘The vibration response and noise caused by subway trains can affect the safety and comfort of superstructures.To study the dynamic response characteristics of subway stations and superstructures under train loads with a hard combination,a numerical model is developed in this study.The indoor model test verified the accuracy of the numerical model.The influence laws of different hard combinations,train operating speeds and modes were studied and evaluated accordingly.The results show that the frequency corresponding to the peak vibration acceleration level of each floor of the superstructure property is concentrated at 10–20 Hz.The vibration response decreases in the high-frequency parts and increases in the lowfrequency parts with increasing distance from the source.Furthermore,the factors,such as train operating speed,operating mode,and hard combination type,will affect the vibration of the superstructure.The vibration response under the reversible operation of the train is greater than that of the unidirectional operation.The operating speed of the train is proportional to its vibration response.The vibration amplification area appears between the middle and the top of the superstructure at a higher train speed.Its vibration acceleration level will exceed the limit value of relevant regulations,and vibration-damping measures are required.Within the scope of application,this study provides some suggestions for constructing subway stations and superstructures.
文摘The Hongyancun subway station in Chongqing,China,is 116 meters deep and the difference in air pressure often leaves users with clogged(堵塞的)ears when accessed via its elevator.When the air pressure outside the eardrum(耳膜)becomes different than the pressure inside,you experience ear barotrauma(气压伤).It occurs most often during steep ascents and descents and is usually associated with plane take⁃offs and landings,or driving up or down mountains.Most subway stations dont usually cause ear barotrauma,because they arent deep or steep enough for your ears to register a significant enough difference in air pressure.But taking the elevator to reach Chinas deepest subway station might actually clog up your ears.Thats because it is located 116 meters below the surface,which is the equivalent of about 40 floors underground.
基金National Natural Science Foundation of China under Grant No.52108473Project of Shaanxi Engineering Technology Research Center for Urban Geology and Underground Space under Grant No.2025KT-03Key Project of Education Department of Shaanxi Province under Grant No.23JY042。
文摘Ground fissure,as a common geo-hazard,impairs the integrity of the site soil and affects the seismic performance of engineering structures.In this paper,a finite element(FE)model for subway stations in a ground fissure area was developed and validated by using experimental results.Numerical analyses were conducted to investigate the seismic response and failure mode of subway stations in a ground fissure area with different locations.Effects of ground fissure on deformations and internal forces of a station,soil pressures and soil plastic strains were discussed.The results showed that the seismic response of the station was significantly amplified by the ground fissure,and stations in the ground fissure area displayed obvious rocking deformation during earthquakes as compared to those in the area without fissures.It also was found that the soil yielding around the station,the dislocation occurring in the ground fissure area,and the dynamic amplification effect were more significant under vertical ground motion,which weakened the station’s ductility and accelerated its destruction process.
文摘This study examines the variations in noise levels across various subway lines in Singapore and three other cities,and provides a detailed overview of the trends and factors influencing subway noise.Most of the equivalent sound pressure level(Leq)in typical subway cabins across the Singapore subway lines are below 85 dBA,with some notable exceptions.These variations in noise levels are influenced by several factors,including rolling stock structure,track conditions and environmental and aerodynamic factors.The spectrogram analysis indicates that the cabin noise is mostly concentrated below the frequency of 1,000 Hz.This study also analyzes cabin noise in subway systems in Suzhou,Seoul,and Tokyo to allow for broader comparisons.It studies the impact of factors such as stock materials,track conditions including the quality of the rails,the presence of curves or irregularities,and maintenance frequency on cabin noise.
基金supported by the Science and Technology Development Project of China Railway Design Corporation(Project No.2024CJ0401).
文摘Based on the distribution of cooling load at a subway station and the peak-valley electricity price in Guangzhou,a chilled water storage system is reserved in the ample space above the station's distribution area.This study proposes a design scheme and operational strategy for a chilled water storage system suitable for subway engineering,based on calculating the cooling load and designing a chilled water storage system in a subway station.Additionally,it proposes calculation coefficients of hourly cooling load suitable for subway engineering and convenient for estimation of hourly cooling load.Furthermore,an economic analysis is conducted by combining hourly cooling load with time-of-use electricity prices.This study provides a reference for the design and application of chilled water storage systems in subsequent subway projects.
基金Beijing Natural Science Foundation-Fengtai Rail Transit Frontier Research Joint Foundation(No.L211024),the National Natural Science Foundation of China(No.52072012).
文摘To explore the influence of emergency evacuation signs on passenger behavior during subway fires and improve evacuation efficiency in emergencies,this paper proposes a dynamic emergency evacuation sign system.A simulation platform integrating building information modeling(BIM)and virtual reality(VR)technologies was em-ployed to create subway fire evacuation scenarios using both the current and proposed dynamic emergency evacuation signage systems.Through simulation experiments,fine-grained microscopic data on passenger behavior was collected.Seven indicators were selected to assess evacuation efficiency and wayfinding difficulty.The analysis explored the influence of evacuation signs on passenger behavior in both overall and decision-making areas,thereby validating the effectiveness of the new emergency evacuation signage system.The results show that the dynamic evacuation signage system significantly improves overall passenger evacuation efficiency and reduces decision-making errors.It also improves wayfinding efficiency in critical decision areas by reducing the need for direction identification,minimizing stopping times,and lowering the frequency of decision errors.The method for evaluating the effects of emergency evacuation signs on passenger evacuation behavior proposed in this study provides a robust theoretical basis for the design and optimization of emergency-oriented signs.
基金supported by the State Key Development Program for Basic Research of China (Grant Nos. 2006CB601007 and 2011CBA00106)the National Natural Science Foundation of China (Grant No. 10674006)the National High Technology Research and Development Program of China (Grant Nos. 2007AA03Z238 and 2007AA03Z213)
文摘In order to eliminate the influence of the large-amplitude magnetic field noise that has complicated magnetocardio- graphic studies since October 2009, we have performed high-accuracy measurement of the environmental magnetic field noise in the vicinity of Beijing Subway Line 4 using a three-component height Tc radio frequency （rf） superconducting quantum interference device （SQUID）. By analysing the spatial form and other characteristics of the time and the fre- quency domains and by calculating the circumferential magnetic field distribution based on a duel-end feeding system model, we reach the following conclusions： （i） the main source of magnetic field noise is the magnetic field generated by thel subway trains, and （ii） the magnetic field interference results mainly from the imbalance between traction current and return rail current that is caused by the leakage current.
文摘In rebuilding Tianjin Metro, numerical simulations are performed to evaluate the original design of the ventilation system of Southwest Station and a new system is given to optimize the velocity and temperature fields at the station. Field measurements are conducted to validate the turbulence model and acquire boundary conditions. The simulation result tallies with testing data on the sport that is found that two-equation turbulence model is acceptable in simulating complex flow at the station. A method of simplifying the simulation of the transient flow at the station into steady flow is used and the validation criterion for this simulation is also given.
文摘The internal flow field study of car compartments is an important step in railroad vehicle design and optimization. The flow field profile has a significant impact on the temperature distribution and passenger comfort level. Experimental studies on flow field can yield accurate results but carry a high time and computational cost. In contrast, the numerical simulation method can yield an internal flow field profile in less time than an experimental study. This study aims to improve the computational efficiency of numerical simulation by adapting two simplified models—the porous media model and the porous jump face model—to study the internal flow field of a railroad car compartment. The results provided by both simplified models are compared with the original numerical simulation model and with experimental data. Based on the results, the porous media model has a better agreement with the original model and with the experimental results. The flow field parameters (temperature and velocity) of the porous media model have relatively small numerical errors, with a maximum numerical error of 4.7%. The difference between the numerical results of the original model and those of the porous media model is less than 1%. By replacing the original numerical simulation model with the porous media model, the flow field of subway car compartments can be calculated with a reduction of about 25% in computing resources, while maintaining good accuracy.
文摘Construction of metro tunnels in dense and crowded urban areas is faced with many risks, such as sub- sidence. The purpose of this paper was the prediction of subsidence risk by failure mode and effect anal- ysis （FMEA） and fuzzy inference system （FIS）. Fuzzy theory will be able to model uncertainties. Fuzzy FMEA provides a tool that can work in a better way with vague concepts and without sufficient informa- tion than conventional FMEA. In this paper, S and D are obtained from fuzzy rules and 0 is obtained from artificial neural network （ANN）. FMEA is performed by developing a fuzzy risk priority number （FRPN）. The FRPN for two stations in Tehran No.4 subway line is 3.1 and 5.5, respectively. To investigate the suit- ability of this approach, the predictions by FMEA have been compared with actual data. The results show that this method can be useful in the prediction of subsidence risk in urban tunnels.
文摘Background:Since the 1970 s,terrorist bombings in subways have been frequently occurring worldwide.To cope with this threat and to provide medical response countermeasures,we analyzed the characteristics of subway bombing terrorist attacks and used the Haddon matrix to explore medical response strategies.Methods:First,we analyzed 111 subway bombings from 1970 to 2017 recorded in the Global Terrorism Database to provide a reference for the strategy exploration.Then,we convened an expert panel to use the Haddon matrix to explore the medical response strategies to subway bombings.Results:In recent decades,at least one bombing attack occurs every 3 years.Summarized by the Haddon matrix,the influencing factors of medical responses to conventional subway bombings include the adequacy of first-aid kits and the medical evacuation equipment,the traffic conditions affecting the evacuation,the continuity and stability of communication,as well as the factors exclusively attributed to dirty bomb attacks in subways,such as ionizing radiation protection capabilities,the structure of the radiation sickness treatment network based on the subway lines,and the disposal of radioactive sewage.These factors form the basis of the strategy discussion.Conclusions:Since subway bombings are long-term threats,it is necessary to have proper medical response preparation.Based on the Haddon matrix,we explored the medical response strategies for terrorist subway bombings,especially dirty bomb attacks.Haddon matrix can help policymakers systematically find the most important factors,which makes the preparations of the response more efficient.
基金Project supported by the National Natural Science Foundation of China (Nos. 51178418 and 51222803)the National Key Technology R&D (863) Program of China (No. 2009BAG12A01-B12-3)
文摘In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,wave propagation in the infinitely extended ground is dealt with using a simple,yet efficient gradually damped artificial boundary.Based on the assumption of invariant geometry and material distribution in the tunnel's direction,the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number.Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number.The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform.The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum.A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed.
基金supported in part by the NSFC project under grant No.61132003the Fundamental Research Funds for the Central Universities(2013JBZ002)the Ph.D.Program Foundation of Ministry of Education of China under grant No.20120009130002
文摘There is an increasing demand on wireless communications in subway tunnels to provide video surveillance and sensory data for security,maintenance and train control,and to offer various communication or entertainment services(e.g.,Internet,etc.) to passengers as well.The wireless channel in tunnels is quite unique due to the confined space and the waveguide effects.Therefore,modeling the radio channel characteristics in tunnels is critically important for communication systems design or optimization.This paper investigates the key radio channel characteristics of a subway tunnel at 2.4 GHz and 5 GHz,such as the path loss,root mean square(RMS) delay spread,channel stationarity,Doppler shift,and channel capacity.The field measurements show that channel characteristics in tunnels are highly location-dependent and there exist abundant components in Doppler shift domain.In the straight section of the subway tunnel,the measured path loss exponents are close to1.6,lower than that in free space.
基金Project(09JJ1008) supported by Hunan Provincial Science Foundation of China
文摘Based on the image theory,the analytical solutions of tunneling-induced ground displacement were derived in conjunction with the nonuniform convergence model.The reasonable value of Poisson ratio in the analytical solution was discussed.The ground settlement width parameter which could reflect the ground condition was introduced to modify the analytical solutions proposed above,and new analytical solutions were presented.To evaluate the validity of the present solutions using the nonuniform convergence model,the results were compared with the observed values for four engineering projects,including 38 measured data of ground settlement.The agreement shows that the present solutions using the nonuniform convergence model are effective for evaluating the tunneling-induced ground displacements.
