Based on the natural and social conditions as well as hydrogeological characteristics of the Ryukyu limestone, a major aquifer in the Ryukyu Islands, a conception of underground dam, was proposed in the early 1970s in...Based on the natural and social conditions as well as hydrogeological characteristics of the Ryukyu limestone, a major aquifer in the Ryukyu Islands, a conception of underground dam, was proposed in the early 1970s in order to develop ground water resources in the Quaternary Ryukyu limestone regions of Japan. The practice of nearly thirty years has shown that the underground dam is an environment-friendly and effective way for developing ground water in these regions.展开更多
Over the last decades,geo-structures are experiencing a rapid development in China.The potential risks inherent in the huge amount of construction and asset operation projects in China were well managed in the major p...Over the last decades,geo-structures are experiencing a rapid development in China.The potential risks inherent in the huge amount of construction and asset operation projects in China were well managed in the major project,i.e.the project of Shanghai Yangtze tunnel in 2002.Since then,risk assessment of geostructures has been gradually developed from a qualitative manner to a quantitative manner.However,the current practices of risk management have been paid considerable attention to the assessment,but little on risk control.As a result,the responses to risks occurrences after a comprehensive assessment are basically too late.In this paper,a smart system for risk sensing incorporating the wireless sensor network(WSN) on-site visualization techniques and the resilience-based repair strategy was proposed.The merit of this system is the real-time monitoring for geo-structural performance and dynamic pre-warning for safety of on-site workers.The sectional convergence,joint opening,and seepage of segmental lining of shield tunnel were monitored by the micro-electro-mechanical systems(MEMS) based sensors.The light emitting diode(LED) coupling with the above WSN system was used to indicate different risk levels on site.By sensing the risks and telling the risks in real time,the geo-risks could be controlled and the safety of geo-structures could be assured to a certain degree.Finally,a resilience-based analysis model was proposed for designing the repair strategy by using the measured data from the WSN system.The application and efficiency of this system have been validated by two cases including Shanghai metro tunnel and underwater road tunnel.展开更多
This paper investigates the response of a maglev structure to three under-crossing tunnels of the Shanghai Metro Line 13.The minimal distance between the tunnels and pile groups of the maglev structure is only 1.5 m,t...This paper investigates the response of a maglev structure to three under-crossing tunnels of the Shanghai Metro Line 13.The minimal distance between the tunnels and pile groups of the maglev structure is only 1.5 m,thus the deformations of the maglev structure are strictly controlled for the serviceability of the operating maglev trains.The displacements of maglev piers and ground settlements during different tunnelling stages are monitored with an automatic measuring system.Based on the observed data,the ground settlement trough and displacements of maglev piers caused by the three shield tunnelling procedures are analyzed and discussed.The maximal ground settlement after the completion of the three tunnelling procedures is -43 mm.To operate the existing maglev safely,practical construction control methods are applied,including synchronous grouting,adjustment of the shield status,shield-advancing speed control,and stabilisation of the soil chamber pressure.With these countermeasures,the tunnel-induced deformations of maglev piers are well below the predefined thresholds.All piers heave under the strict deformation criterion of 2.0 mm.The crossing project is finally completed without interruptions of the maglev operations by monitoring the progress.The presented project is a valuable example for the evaluation of shield tunnelling effects on the adjacent maglev structures and establishes criteria for similar projects in the future.展开更多
The Random Decrement Technique （RDT）, based on decentralized computing approaches implemented in wireless sensor networks （WSNs）, has shown advantages for modal parameter and data aggregation identification. Howev...The Random Decrement Technique （RDT）, based on decentralized computing approaches implemented in wireless sensor networks （WSNs）, has shown advantages for modal parameter and data aggregation identification. However, previous studies of RDT-based approaches from ambient vibration data are based on the assumption of a broad-band stochastic process input excitation. The process normally is modeled by filtered white or white noise. In addition, the choice of the triggering condition in RDT is closely related to data communication. In this project, research has been conducted to study the nonstationary white noise excitations as the input to verify the random decrement technique. A local extremum triggering condition is chosen and implemented for the purpose of minimum data communication in a RDT-based distributed computing strategy. Numerical simulation results show that the proposed technique is capable of minimizing the amount of data transmitted over the network with accuracy in modal parameters identification.展开更多
This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dy...This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.展开更多
文摘Based on the natural and social conditions as well as hydrogeological characteristics of the Ryukyu limestone, a major aquifer in the Ryukyu Islands, a conception of underground dam, was proposed in the early 1970s in order to develop ground water resources in the Quaternary Ryukyu limestone regions of Japan. The practice of nearly thirty years has shown that the underground dam is an environment-friendly and effective way for developing ground water in these regions.
基金supported by the National Natural Science Foundation of China(Grant Nos.51278381,51538009 and 51608380)the International Research Cooperation Project of Shanghai Science and Technology Committee(Grant No.15220721600)the Peak Discipline Construction on Civil Engineering of Shanghai Project
文摘Over the last decades,geo-structures are experiencing a rapid development in China.The potential risks inherent in the huge amount of construction and asset operation projects in China were well managed in the major project,i.e.the project of Shanghai Yangtze tunnel in 2002.Since then,risk assessment of geostructures has been gradually developed from a qualitative manner to a quantitative manner.However,the current practices of risk management have been paid considerable attention to the assessment,but little on risk control.As a result,the responses to risks occurrences after a comprehensive assessment are basically too late.In this paper,a smart system for risk sensing incorporating the wireless sensor network(WSN) on-site visualization techniques and the resilience-based repair strategy was proposed.The merit of this system is the real-time monitoring for geo-structural performance and dynamic pre-warning for safety of on-site workers.The sectional convergence,joint opening,and seepage of segmental lining of shield tunnel were monitored by the micro-electro-mechanical systems(MEMS) based sensors.The light emitting diode(LED) coupling with the above WSN system was used to indicate different risk levels on site.By sensing the risks and telling the risks in real time,the geo-risks could be controlled and the safety of geo-structures could be assured to a certain degree.Finally,a resilience-based analysis model was proposed for designing the repair strategy by using the measured data from the WSN system.The application and efficiency of this system have been validated by two cases including Shanghai metro tunnel and underwater road tunnel.
基金financially supported by National Natural Science Foundation of China,China(Grants Nos.51978517,41772295,52090082,and 52108381)Innovation Program of Shanghai Municipal Education Commission(Grant No.2019-01-07-00-07-456 E00051)+2 种基金Shanghai Science and Technology Committee,China Program(Grants Nos.21DZ1200601,20DZ1201404)National Key Research and Development Program of China(Grant No.2021YFF0502200)China Postdoctoral Science Foundation,China(Grant No.2021M702491).
文摘This paper investigates the response of a maglev structure to three under-crossing tunnels of the Shanghai Metro Line 13.The minimal distance between the tunnels and pile groups of the maglev structure is only 1.5 m,thus the deformations of the maglev structure are strictly controlled for the serviceability of the operating maglev trains.The displacements of maglev piers and ground settlements during different tunnelling stages are monitored with an automatic measuring system.Based on the observed data,the ground settlement trough and displacements of maglev piers caused by the three shield tunnelling procedures are analyzed and discussed.The maximal ground settlement after the completion of the three tunnelling procedures is -43 mm.To operate the existing maglev safely,practical construction control methods are applied,including synchronous grouting,adjustment of the shield status,shield-advancing speed control,and stabilisation of the soil chamber pressure.With these countermeasures,the tunnel-induced deformations of maglev piers are well below the predefined thresholds.All piers heave under the strict deformation criterion of 2.0 mm.The crossing project is finally completed without interruptions of the maglev operations by monitoring the progress.The presented project is a valuable example for the evaluation of shield tunnelling effects on the adjacent maglev structures and establishes criteria for similar projects in the future.
基金Projects(42077254, 51874144) supported by the National Natural Science Foundation of ChinaProjects(cstc2019jcyjmsxm X0488, cstc2021jcyj-msxm X0354) supported by the Natural Science Foundation of Chongqing,China+2 种基金Projects(KJZD-K202201304, KJQN202201314) supported by Science and Technology of Chongqing Municipal Education Commission,ChinaProject (2021M693751) supported by China Postdoctoral Science FoundationProject (P2017JG18) supported by Major Cultivation of Chongqing University of Arts and Sciences,China。
基金National Key Technology R&D Program of China under Grant No.2014BAL05B06Guangdong Science&Technology Program under Grant No.2014A050503016the Shenzhen Science&Technology Program under Grant No.GJHZ20150312114346635
文摘The Random Decrement Technique （RDT）, based on decentralized computing approaches implemented in wireless sensor networks （WSNs）, has shown advantages for modal parameter and data aggregation identification. However, previous studies of RDT-based approaches from ambient vibration data are based on the assumption of a broad-band stochastic process input excitation. The process normally is modeled by filtered white or white noise. In addition, the choice of the triggering condition in RDT is closely related to data communication. In this project, research has been conducted to study the nonstationary white noise excitations as the input to verify the random decrement technique. A local extremum triggering condition is chosen and implemented for the purpose of minimum data communication in a RDT-based distributed computing strategy. Numerical simulation results show that the proposed technique is capable of minimizing the amount of data transmitted over the network with accuracy in modal parameters identification.
文摘This paper gives an insight on the effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system＇s steady state and dynamic performance. The impact of dynamic load models on system stability is also studied. The steady-state and dynamic stability simulation results of a 39 bus system for constant line impedance （the traditional simulation practice） are compared to the results with estimated, but realistic, temperature varied line impedances using PSLF （positive sequence load flow） software. The modulated line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electro-mechanical oscillations at generator buses.
