In this paper, we show some recent experimental applications of Brillouin optical time-domain analysis(BOTDA) based sensors for geotechnical monitoring. In particular, how these sensors can be applied to detecting ear...In this paper, we show some recent experimental applications of Brillouin optical time-domain analysis(BOTDA) based sensors for geotechnical monitoring. In particular, how these sensors can be applied to detecting early movements of soil slopes by the direct embedding of suitable fiber cables in the ground is presented. Furthermore, the same technology can be used to realize innovative inclinometers, as well as smart foundation anchors.展开更多
In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic senso...In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic sensors have a variety of exclusive advantages, such as smaller size,higher precision, and better corrosion resistance.These innovative monitoring technologies have been successfully applied for performance monitoring of geo-structures and early warning of potential geohazards around the world. In order to investigate their ability to monitor slope stability problems, a medium-sized model of soil nailed slope has been constructed in laboratory. The fully distributed Brillouin optical time-domain analysis(BOTDA)sensing technology was employed to measure the horizontal strain distributions inside the model slope.During model construction, a specially designed strain sensing fiber was buried in the soil mass.Afterward, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and a reaction frame. During testing, an NBX-6050 BOTDA sensing interrogator was used to collect the fiber optic sensing data. The test results have been analyzed in detail, which shows that the fiber optic sensors can capture the progressive deformation and failure pattern of the model slope. The limit equilibrium analyses were also conducted to obtain the factors of safety of the slope under different surface loadings. It is found that the characteristic maximum strains can reflect the stability of the model slope and an empirical relationship was obtained. This study verified the effectiveness of the distributed BOTDA sensing technology in performance monitoring of slope.展开更多
Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The prin...Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The principle of the proposed technique to reduce the fading noise is introduced based on the analysis of Rayleigh Brillouin optical time domain analysis system. The experimental results show that the signal-to-noise ratio(SNR) at the end of optical fiber with length of 50 m after 17 times wavelength scanning is 5.21 d B higher than that with single wavelength, the Brillouin frequency shift(BFS) on the heated fiber with length of 70 m inserted at the center of sensing fiber can be accurately measured as 0.19 MHz, which is equivalent to a measurement accuracy of 0.19 °C. It indicates that the proposed technique can realize high-accuracy temperature measurement and has huge potential in the field of long-distance and high-accuracy sensing.展开更多
针对广东珠三角地区部分变电站存在地质基础沉降需要监测的问题,提出了一种基于分布式光传感技术、使用应力光缆的变电站地质基础沉降监测方法。该方法的技术原理是布里渊光时域分析(Brillouin optical time domain analysis,BOTDA)技术...针对广东珠三角地区部分变电站存在地质基础沉降需要监测的问题,提出了一种基于分布式光传感技术、使用应力光缆的变电站地质基础沉降监测方法。该方法的技术原理是布里渊光时域分析(Brillouin optical time domain analysis,BOTDA)技术,监测硬件系统的构成包括光路系统和电路系统,应力光缆选择定点式应变感测光缆,布线方案包括变电站地表敷设和桩孔光缆入地。模拟试验表明,BOTDA技术能够适应变电站地质基础沉降监测的需要,布设应力光缆的同时要布设温度参考光纤或光缆,做好温度补偿。研究结果证明了该方案的可行性,为变电站防治地质基础沉降灾害提供了一种辅助决策和效果评估手段。展开更多
文摘In this paper, we show some recent experimental applications of Brillouin optical time-domain analysis(BOTDA) based sensors for geotechnical monitoring. In particular, how these sensors can be applied to detecting early movements of soil slopes by the direct embedding of suitable fiber cables in the ground is presented. Furthermore, the same technology can be used to realize innovative inclinometers, as well as smart foundation anchors.
基金the financial support provided by the National Basic Research Program of China (973 Program) (Grant No. 2011CB710605)the National Natural Science Foundation of China (Grant Nos. 41102174, 41302217)supported by the National Key Technology R&D Program of China (Grant No. 2012BAK10B05)
文摘In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic sensors have a variety of exclusive advantages, such as smaller size,higher precision, and better corrosion resistance.These innovative monitoring technologies have been successfully applied for performance monitoring of geo-structures and early warning of potential geohazards around the world. In order to investigate their ability to monitor slope stability problems, a medium-sized model of soil nailed slope has been constructed in laboratory. The fully distributed Brillouin optical time-domain analysis(BOTDA)sensing technology was employed to measure the horizontal strain distributions inside the model slope.During model construction, a specially designed strain sensing fiber was buried in the soil mass.Afterward, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and a reaction frame. During testing, an NBX-6050 BOTDA sensing interrogator was used to collect the fiber optic sensing data. The test results have been analyzed in detail, which shows that the fiber optic sensors can capture the progressive deformation and failure pattern of the model slope. The limit equilibrium analyses were also conducted to obtain the factors of safety of the slope under different surface loadings. It is found that the characteristic maximum strains can reflect the stability of the model slope and an empirical relationship was obtained. This study verified the effectiveness of the distributed BOTDA sensing technology in performance monitoring of slope.
基金supported by the National Natural Science Foundation of China(No.61377088)the Natural Science Foundation of Hebei Province of China(Nos.E2015502053 and F2015502059)the Fundamental Research Funds for the Central Universities(No.2016XS104)
文摘Aiming at the problem of large fading noise in Rayleigh Brillouin optical time domain analysis system, a wavelength scanning technique is proposed to enhance the performance of the temperature sensing system. The principle of the proposed technique to reduce the fading noise is introduced based on the analysis of Rayleigh Brillouin optical time domain analysis system. The experimental results show that the signal-to-noise ratio(SNR) at the end of optical fiber with length of 50 m after 17 times wavelength scanning is 5.21 d B higher than that with single wavelength, the Brillouin frequency shift(BFS) on the heated fiber with length of 70 m inserted at the center of sensing fiber can be accurately measured as 0.19 MHz, which is equivalent to a measurement accuracy of 0.19 °C. It indicates that the proposed technique can realize high-accuracy temperature measurement and has huge potential in the field of long-distance and high-accuracy sensing.
文摘针对广东珠三角地区部分变电站存在地质基础沉降需要监测的问题,提出了一种基于分布式光传感技术、使用应力光缆的变电站地质基础沉降监测方法。该方法的技术原理是布里渊光时域分析(Brillouin optical time domain analysis,BOTDA)技术,监测硬件系统的构成包括光路系统和电路系统,应力光缆选择定点式应变感测光缆,布线方案包括变电站地表敷设和桩孔光缆入地。模拟试验表明,BOTDA技术能够适应变电站地质基础沉降监测的需要,布设应力光缆的同时要布设温度参考光纤或光缆,做好温度补偿。研究结果证明了该方案的可行性,为变电站防治地质基础沉降灾害提供了一种辅助决策和效果评估手段。
