Monitoring pressure and thermal strain in the second lining of a tunnel with a Brillouin OTDR

Li, Chuan; Sun, Yu; Zhao, Youxuan; Liu, Hao; Gao, Liming; Zhang, Zhiling; Qiu, Haitao

doi:10.1088/0964-1726/15/5/n01

Cited by 10 publications

(5 citation statements)

References 3 publications

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“…These technologies have shown unique advantages over conventional monitoring methods, including tiny size, high sensitivity, immunity to EMI, good durability, and the ability of multiplexing. The early-stage study on the feasibility of fiber optic sensing in tunnel monitoring was introduced by Mohamad et al [8], Wang et al [9], and Li et al [10]. It is shown that there is certain discrepancy between field measurement data of strain distribution and theoretical results.…”

Section: Introductionmentioning

confidence: 99%

The Mechanical Performance of Shear Key of Immersed Tube Tunnel with Differential Foundation Settlement

2016

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A fiber Bragg grating (FBG) based sensor network was developed to monitor the strain distributions within immersed tube tunnel shear key, which was subjected to differential settlements. An improved packaging and installation method of the quasi-distributed sensor system was utilized, which not only ensured a high sensor survival rate but also achieved accurate measurement of axial strains. Based on the monitoring results, the stress variations of shear keys of the immersed tunnel joint, which originate from the buckling caused by the longitudinal differential siltation at seabed and the surface defects, were analyzed in detail.

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Section: Introductionmentioning

confidence: 99%

The Mechanical Performance of Shear Key of Immersed Tube Tunnel with Differential Foundation Settlement

2016

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“…These technologies enable simultaneous measurement of strain and temperature distributions along an optical fiber up to several kilometers, which is very attractive for geotechnical monitoring [9][10][11]. Recently they have been successfully applied to performance monitoring of a variety of geotechnical-related structures, including natural and man-made slopes [2,3,[12][13][14][15][16], deep and shallow foundations [17][18][19], embankments and dams [20][21][22], and tunnels and excavations [23][24][25][26][27]. These applications have demonstrated the exceptional features of distributed fiber-optic sensing technologies, such as long-distance measurement, high repeatability, and superior corrosion resistance.…”

Section: Introductionmentioning

confidence: 99%

Interfacial characterization of soil-embedded optical fiber for ground deformation measurement

Zhang

Zhu

Shi

et al. 2014

Smart Mater. Struct.

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Recently fiber-optic sensing technologies have been applied for performance monitoring of geotechnical structures such as slopes, foundations, and retaining walls. However, the validity of measured data from soil-embedded optical fibers is strongly influenced by the properties of the interface between the sensing fiber and the soil mass. This paper presents a study of the interfacial properties of an optical fiber embedded in soil with an emphasis on the effect of overburden pressure. Laboratory pullout tests were conducted to investigate the load-deformation characteristics of a 0.9 mm tight-buffered optical fiber embedded in soil. Based on a tri-linear interfacial shear stress-displacement relationship, an analytical model was derived to describe the progressive pullout behavior of an optical fiber from soil matrix. A comparison between the experimental and predicted results verified the effectiveness of the proposed pullout model. The test results are further interpreted and discussed. It is found that the interfacial bond between an optical fiber and soil is prominently enhanced under high overburden pressures. The apparent coefficients of friction of the optical fiber/soil interface decrease as the overburden pressure increases, due to the restrained soil dilation around the optical fiber. Furthermore, to facilitate the analysis of strain measurement, three working states of a soil-embedded sensing fiber were defined in terms of two characteristic displacements.

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“…Compared with electrical sensors, FOS have many advantages, such as high accuracy and a high resolution, a tiny size, and resistance to EMI; even more importantly, the sensors can be connected into series in a single fiber [ 4 , 5 ]. Some researchers have used FOS to measure temperature [ 6 ], strain [ 7 , 8 ], deformation [ 9 , 10 ], water pressure [ 11 ], liquid level [ 12 , 13 , 14 , 15 ], humidity [ 16 ], and soil pressure [ 17 ]. Fiber Bragg grating (FBG) is one of the most widely used FOS technologies, due to its high accuracy and inexpensive data interrogation.…”

Section: Introductionmentioning

confidence: 99%

A Newly Designed Fiber-Optic Based Earth Pressure Transducer with Adjustable Measurement Range

Wei

Meng

2018

Sensors

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A novel fiber-optic based earth pressure sensor (FPS) with an adjustable measurement range and high sensitivity is developed to measure earth pressures for civil infrastructures. The new FPS combines a cantilever beam with fiber Bragg grating (FBG) sensors and a flexible membrane. Compared with a traditional pressure transducer with a dual diaphragm design, the proposed FPS has a larger measurement range and shows high accuracy. The working principles, parameter design, fabrication methods, and laboratory calibration tests are explained in this paper. A theoretical solution is derived to obtain the relationship between the applied pressure and strain of the FBG sensors. In addition, a finite element model is established to analyze the mechanical behavior of the membrane and the cantilever beam and thereby obtain optimal parameters. The cantilever beam is 40 mm long, 15 mm wide, and 1 mm thick. The whole FPS has a diameter of 100 mm and a thickness of 30 mm. The sensitivity of the FPS is 0.104 kPa/με. In addition, automatic temperature compensation can be achieved. The FPS’s sensitivity, physical properties, and response to applied pressure are extensively examined through modeling and experiments. The results show that the proposed FPS has numerous potential applications in soil pressure measurement.

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Monitoring pressure and thermal strain in the second lining of a tunnel with a Brillouin OTDR

Cited by 10 publications

References 3 publications

The Mechanical Performance of Shear Key of Immersed Tube Tunnel with Differential Foundation Settlement

The Mechanical Performance of Shear Key of Immersed Tube Tunnel with Differential Foundation Settlement

Interfacial characterization of soil-embedded optical fiber for ground deformation measurement

A Newly Designed Fiber-Optic Based Earth Pressure Transducer with Adjustable Measurement Range

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