Distributed Strain Monitoring in Tunnel Shotcrete (with and without yieldable concrete wedges) by fiber-based TW-COTDR technique

Planes, I.; Girard, Sylvain; Boukenter, Aziz; Marin, Emmanuel; Delépine-Lesoille, Sylvie; Farhoud, Radwan; Zghondi, Jad; Fischli, Frank; Ouerdane, Y.

doi:10.1364/apos.2016.f1a.4

Cited by 1 publication

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“…More recently, the strain sensitivity of the sensing cables were characterized. As detailed in [ 23 ], they may differ from the optical fibre’ sensitivity. For instance, following the methodology described in Section 3.2.5, Rayleigh strain coefficients of 0.79 µε −1 for the optical fibre versus 0.77 µε −1 for the fibre cable were obtained.…”

Section: Results On Distributed Strain Measurementsmentioning

confidence: 99%

“…Feasibility of implementation in the shotcrete layer has been demonstrated in the GER gallery. FOS distributed strain measurements showed a good correlation with VWE’s [ 23 ]. However, as expected due to high strain in the shotcrete, the optical loop became too noisy after the first days, forbidding the use of stimulated Brillouin measurements.…”

Section: Results On Distributed Strain Measurementsmentioning

confidence: 99%

“…Finally, more robust bench designs must be used when sensing cables (opposite to optical fibres in primary coating), have to be characterized. Previous studies [ 23 ] demonstrated that the fibre strain coefficients of the Rayleigh and Brillouin responses are affected by the fibre packaging. Andra has used the testing bench of the Marmota company (Zurich, Switzerland), illustrated in Figure 8 to characterize the coefficients of the fibre cable.…”

Section: Methodsmentioning

confidence: 99%

“… Schematic representation ( left ) of the bench used to determine fibre optic cables’ sensitivities to strain and pictures ( right ) from Marmota Company. Adapted with permission from [ 23 ]. Copyright 2016 Optical Society of America Publishing.…”

Section: Figurementioning

confidence: 99%

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France’s State of the Art Distributed Optical Fibre Sensors Qualified for the Monitoring of the French Underground Repository for High Level and Intermediate Level Long Lived Radioactive Wastes

Delépine-Lesoille

Girard

Landolt

et al. 2017

Sensors

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This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.

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Section: Results On Distributed Strain Measurementsmentioning

confidence: 99%

Section: Results On Distributed Strain Measurementsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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