Distributed Fiber Optic Sensing along Grouted Anchors to Assess Curvature and Bending Characteristics

Monsberger, Christoph; Lienhart, Werner; Caporossi, Paolo

doi:10.1364/ofs.2018.tue98

Cited by 2 publications

(2 citation statements)

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“…The special grout used to cement the strands is effective also for the fibres' coupling, avoiding the use of additional treatment. With respect to other recent installation procedures [35], long bars can be easily produced and instrumented. Finally, the spatial resolution that can be obtained employing OFDR is at least one order of magnitude better than that of Brillouin-based techniques [32,34].…”

Section: Coupling the Fibre To The Composite Barsmentioning

confidence: 99%

“…They exploited a Brillouin optical time domain analysis (BOTDA) technique with positive results, but limited spatial resolution (0.4 m), concluding that other fully distributed sensing technologies should be used to verify the present sensor performance. More recently, Monsberger et al [35] used the OFDR technique to measure the strain and curvature of 5 m-long steel grouted anchors with a very high spatial resolution. The steel bars, 26 mm in diameter, were equipped with optical fibres cemented in two longitudinal grooves in opposed positions.…”

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confidence: 99%

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Composite Anchors for Slope Stabilisation: Monitoring of their In-Situ Behaviour with Optical Fibre

et al. 2019

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Composite anchors are special passive sub-horizontal reinforcements recently developed for remediation of unstable slopes. They are composed of a hollow steel bar, installed by a self-drilling technique in the soil, coupled with tendons cemented in the inner hole to increase the global anchor tensile strength. The anchors are primarily intended to stabilise medium to deep landslides, both in soils or weathered rock masses. Among the valuable advantages of composite anchors are their low cost, ease of installation, and flexibility in execution, as testified by a rapid increase in their use in recent years. The bond strength at the soil-anchor interface is the main parameter for both the design of these reinforcements and the evaluation of their long-term effects for landslide stabilisation. After a brief description of the composite anchor technology, this paper presents a novel methodology for monitoring the strain and stress accumulated in the anchors over time when installed in an unstable slope. The new monitoring system is composed of a distributed fibre optic sensing system, exploiting the optical frequency domain reflectometry (OFDR) technique, to measure the strain exerted on the optical fibre cable embedded with the tendons inside the bar. The system permits an evaluation of the axial force distribution in the anchor and the soil-anchor interface actions with a spatial resolution of up to some millimetres. Therefore, it allows determination of the stabilising capability associated with the specific hydrogeological conditions of the site. Furthermore, upon an extensive validation, the system may become part of a standard practice to be applied in this type of intervention, aimed at evaluating the effectiveness of the anchor installation and its evolution over time.

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Section: Coupling the Fibre To The Composite Barsmentioning

confidence: 99%

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confidence: 99%