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

1
Department of Civil, Environmental and Architectural Engineering (ICEA), University of Padova, 35129 Padua, Italy
2
Research institute for geo-hydrological protection (IRPI), National Research Council, 35127 Padova, Italy
3
Department of Information Engineering (DEI), University of Padova, 35131 Padova, Italy
4
Autoperforanti Sirive®, 36073 Cornedo Vicentino (VI), Italy
*
Author to whom correspondence should be addressed.
Geosciences 2019, 9(5), 240; https://doi.org/10.3390/geosciences9050240
Received: 1 March 2019 / Revised: 28 March 2019 / Accepted: 4 April 2019 / Published: 25 May 2019
(This article belongs to the Special Issue Mountain Landslides: Monitoring, Modeling, and Mitigation)
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Abstract

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. View Full-Text
Keywords: slope stabilisation; passive anchors; distributed optical fibre sensor; soil-anchor interface slope stabilisation; passive anchors; distributed optical fibre sensor; soil-anchor interface
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Cola, S.; Schenato, L.; Brezzi, L.; Tchamaleu Pangop, F.C.; Palmieri, L.; Bisson, A. Composite Anchors for Slope Stabilisation: Monitoring of their In-Situ Behaviour with Optical Fibre. Geosciences 2019, 9, 240.

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