Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature ...Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.展开更多
In this paper, we present a simple and fast spectra inversion method to reconstruct the temperature distribution along single fiber Bragg grating （FBC） temperature sensor. This is a fully distributed sensing method ...In this paper, we present a simple and fast spectra inversion method to reconstruct the temperature distribution along single fiber Bragg grating （FBC） temperature sensor. This is a fully distributed sensing method based on the simulated annealing evolutionary （SAE） algorithm. Several modifications are made to improve the algorithm efficiency, including choosing the most superior chromosome, setting up the boundary of every gene according to the density of resonance peaks of the reflection spectrum, and dynamically modifying the boundary with the algorithm running. Numerical simulation results show that both the convergence rate and the fluctuation are significantly improved. A high spat-ial temperature resolution of 0.25 mm has been achieved at the time cost of 86 s.展开更多
Based on advantages of technology of distributive fiber-optic temperature sensing and specific to its applications in monitoring mine conflagration, the corresponding Processes such as connection arrangement, signal t...Based on advantages of technology of distributive fiber-optic temperature sensing and specific to its applications in monitoring mine conflagration, the corresponding Processes such as connection arrangement, signal transmission and monitoring were illustrated. As applied in Sitai Coal Mine of Datong Coal Mine Group Co., this method is effective and accurate and could provide reliable gist for monitoring spontaneous combustion in gob area of mines.展开更多
A novel nonlinear mirror structure which can increase the optical signal-to-noise ratio of a distributed fiber Raman temperature sensor is proposed, and 6 dB improvement of the optical signal-to-noise ratio is obtaine...A novel nonlinear mirror structure which can increase the optical signal-to-noise ratio of a distributed fiber Raman temperature sensor is proposed, and 6 dB improvement of the optical signal-to-noise ratio is obtained. With the assistance of the nonlinear mirror, we demonstrate that the spatial resolution of the sensor is improved from 3 m to 1 m, and the temperature accuracy is improved from ±0.6℃ to ±0.2℃. The theoretical analysis and the experimental data are in good agreement.展开更多
Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a ...Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.展开更多
Backscattered lightwaves from an optical fibre are used to realise distributed fibre optic sensing(DFOS)systems for measuring various parameters.Rayleigh,Brillouin,and Raman backscattering provide different sensitivit...Backscattered lightwaves from an optical fibre are used to realise distributed fibre optic sensing(DFOS)systems for measuring various parameters.Rayleigh,Brillouin,and Raman backscattering provide different sensitivities to different measurands and have garnered the attention of researchers.A system combining the three principles above can effectively separate the measured strain and temperature completely as well as provide measurements of both dynamic and static parameters.However,the combined system is extremely complicated if the three systems are independent of each other.Hence,we propose a single-end hybrid DFOS system that uses two successive pulses to realise the Brillouin amplification of Rayleigh backscattering lightwaves for combining Rayleigh and Brillouin systems.A 3-bit pulse-coding method is employed to demodulate the Raman scattering of the two pulses to integrate Raman optical time-domain reflectometry into the hybrid system.Using this hybrid scheme,a simultaneous measurement of multiple parameters is realised,and a favourable measurement accuracy is achieved.展开更多
针对注水井分层注水量诊断技术难题,提出基于分布式光纤温度传感(Distributed Temperature Sensing,DTS)的注水井吸水剖面解释方法。建立考虑微量热效应的注水井温度剖面预测模型,模拟分析注水量、注水时间、储层导热系数等7个因素对温...针对注水井分层注水量诊断技术难题,提出基于分布式光纤温度传感(Distributed Temperature Sensing,DTS)的注水井吸水剖面解释方法。建立考虑微量热效应的注水井温度剖面预测模型,模拟分析注水量、注水时间、储层导热系数等7个因素对温度剖面的影响规律。通过正交试验模拟分析,确定不同因素对注水井温度剖面的影响程度从强到弱分别为注入水温度、注水时间、注水量、井筒半径、储层导热系数、井筒倾斜角度、注水层渗透率,明确影响注水井温度剖面的主控因素为注入水温度、注水时间和注入量。采用模拟退火(Simulated Annealing,SA)算法建立注水井DTS数据反演模型,对一口注水井现场实测DTS数据进行反演,获得较为准确的吸水剖面,单层最大吸水量误差百分比14.25%,平均误差11.09%,验证该反演方法的可靠性。通过DTS数据反演可以实现注水井吸水剖面定量解释,为注水效果评价提供直接依据。展开更多
基金The authors grate fully acknowledge the financial support provided by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Open Research Project Program of the State Key Laboratory of Internet of Things for Smart City(University of Macao),China(Grant No.SKUoTSC(UM)-2021-2023/0RP/GA10/2022).
文摘Defects in cast-in-situ piles have an adverse impact on load transfer at the pile‒soil interface and pile bearing capacity. In recent years, thermal integrity profiling (TIP) has been developed to measure temperature profiles of cast-in-situ piles, enabling the detection of structural defects or anomalies at the early stage of construction. However, using this integrity testing method to evaluate potential defects in cast-in-situ piles requires a comprehensive understanding of the mechanism of hydration heat transfer from piles to surrounding soils. In this study, small-scale model tests were conducted in laboratory to investigate the performance of TIP in detecting pile integrity. Fiber-optic distributed temperature sensing (DTS) technology was used to monitor detailed temperature variations along model piles in sand. Additionally, sensors were installed in sand to measure water content and matric suction. An interpretation method against available DTS-based thermal profiles was proposed to reveal the potential defective regions. It shows that the temperature difference between normal and defective piles is more obvious in wet sand. In addition, there is a critical zone of water migration in sand due to the water absorption behavior of cement and temperature transfer-induced water migration in the early-age concrete setting. These findings could provide important insight into the improvement of the TIP testing method for field applications.
基金Project supported by the Development Foundation of the Education Commission of Shanghai Municipality (Grant No.2008CG47)the Cultivation Foundation of the Key Scientific and Technical Innovation Project (Grant No.708041)+2 种基金the Research Foundation for the Doctoral Program of Higher Education Ministry of Education of China (Grant No.20093108120017)the Shanghai Leading Academic Discipline Project (Grant No.S30108)the Natural Science Foundation of Shanghai Municipality (Grant No.09ZR1412200)
文摘In this paper, we present a simple and fast spectra inversion method to reconstruct the temperature distribution along single fiber Bragg grating （FBC） temperature sensor. This is a fully distributed sensing method based on the simulated annealing evolutionary （SAE） algorithm. Several modifications are made to improve the algorithm efficiency, including choosing the most superior chromosome, setting up the boundary of every gene according to the density of resonance peaks of the reflection spectrum, and dynamically modifying the boundary with the algorithm running. Numerical simulation results show that both the convergence rate and the fluctuation are significantly improved. A high spat-ial temperature resolution of 0.25 mm has been achieved at the time cost of 86 s.
基金Supported by the National Natural Science Foundation of China （50375026,50375028）
文摘Based on advantages of technology of distributive fiber-optic temperature sensing and specific to its applications in monitoring mine conflagration, the corresponding Processes such as connection arrangement, signal transmission and monitoring were illustrated. As applied in Sitai Coal Mine of Datong Coal Mine Group Co., this method is effective and accurate and could provide reliable gist for monitoring spontaneous combustion in gob area of mines.
基金supported by the National Natural Science Foundation of China under Grant No.60377021partially supported by Program for New Century Excellent Talents in University under Grant No. NCET-07-0152Sichuan Scientific Funds for Young Researchers under Grant No. 08ZQ026-012.
文摘A novel nonlinear mirror structure which can increase the optical signal-to-noise ratio of a distributed fiber Raman temperature sensor is proposed, and 6 dB improvement of the optical signal-to-noise ratio is obtained. With the assistance of the nonlinear mirror, we demonstrate that the spatial resolution of the sensor is improved from 3 m to 1 m, and the temperature accuracy is improved from ±0.6℃ to ±0.2℃. The theoretical analysis and the experimental data are in good agreement.
基金The financial supports provided by the National Natural Science Foundation of China(Grant Nos.41230636,41372265,41427801)National Basic Research Program of China(973 Project)(Grant No.2011CB710605)
文摘Moisture content is a fundamental physical index that quantifies soil property and is closely associatedwith the hydrological, ecological and engineering behaviors of soil. To measure in-situ soil moisturecontents, a distributed measurement system for in-situ soil moisture content （SM-DTS） is introduced.The system is based on carbon-fiber heated cable （CFHC） technology that has been developed to enhancethe measuring accuracy of in-situ soil moisture content. Using CFHC technique, a temperature characteristicvalue （Tt） can be defined from temperatureetime curves. A relationship among Tt, soil thermalimpedance coefficient and soil moisture content is then established in laboratory. The feasibility of theSM-DTS technology to provide distributed measurements of in-situ soil moisture content is verifiedthrough field tests. The research reported herein indicates that the proposed SM-DTS is capable ofmeasuring in-situ soil moisture content over long distances and large areas.
基金funding from the National Natural Science Foundation of China(NSFC)under grant numbers 61735015,62275151,and the Major Key Project of PCL.
文摘Backscattered lightwaves from an optical fibre are used to realise distributed fibre optic sensing(DFOS)systems for measuring various parameters.Rayleigh,Brillouin,and Raman backscattering provide different sensitivities to different measurands and have garnered the attention of researchers.A system combining the three principles above can effectively separate the measured strain and temperature completely as well as provide measurements of both dynamic and static parameters.However,the combined system is extremely complicated if the three systems are independent of each other.Hence,we propose a single-end hybrid DFOS system that uses two successive pulses to realise the Brillouin amplification of Rayleigh backscattering lightwaves for combining Rayleigh and Brillouin systems.A 3-bit pulse-coding method is employed to demodulate the Raman scattering of the two pulses to integrate Raman optical time-domain reflectometry into the hybrid system.Using this hybrid scheme,a simultaneous measurement of multiple parameters is realised,and a favourable measurement accuracy is achieved.
文摘针对注水井分层注水量诊断技术难题,提出基于分布式光纤温度传感(Distributed Temperature Sensing,DTS)的注水井吸水剖面解释方法。建立考虑微量热效应的注水井温度剖面预测模型,模拟分析注水量、注水时间、储层导热系数等7个因素对温度剖面的影响规律。通过正交试验模拟分析,确定不同因素对注水井温度剖面的影响程度从强到弱分别为注入水温度、注水时间、注水量、井筒半径、储层导热系数、井筒倾斜角度、注水层渗透率,明确影响注水井温度剖面的主控因素为注入水温度、注水时间和注入量。采用模拟退火(Simulated Annealing,SA)算法建立注水井DTS数据反演模型,对一口注水井现场实测DTS数据进行反演,获得较为准确的吸水剖面,单层最大吸水量误差百分比14.25%,平均误差11.09%,验证该反演方法的可靠性。通过DTS数据反演可以实现注水井吸水剖面定量解释,为注水效果评价提供直接依据。
