Distributed Fiber Optic Sensing in Tunneling

In modern tunneling, geotechnical deformation monitoring is an important component to ensure a safe construction and a long lifetime of the tunnel. It is state of the art to measure displacements at the inner lining surface using total stations or terrestrial laser scanners and internal deformations with vibrating wire sensors. However, these measurements do not deliver a complete picture of the capacity within the tunnel lining and new methods must be evolved.

IGMS developed sensing systems based on distributed fiber optic measurements that allow in-situ deformation monitoring in tunneling applications. Depending on the application we use sensing systems based on Rayleigh or Brillouin backscattering. Especially due to the high spatial resolution of about 10 mm of Rayleigh systems, completely new information can be gathered. We embed sensing cables with lengths up to 60 m into precast tunnel lining segments and can therefore observe the utilization grade of the segment at about 6000 positions. Moreover, the high measurement resolution of about 1 µm/m enables the detection of cracks. The suitability of the system is proven with reference measurements, including camera-based systems for crack monitoring and internal pointwise strain measurements with vibrating wire sensors.

In addition to investigations of precast tunnel segments, a modified system for conventional tunneling can be installed in the shotcrete lining directly in the area of the working face in a geological interference zone. After installation, autonomous monitoring can be performed during the curing of the shotcrete and the further excavation of the tunnel over several weeks and in the long term. We have proven the robustness of the system in several field installations at the Semmering Base Tunnel.

Our patented approach for concrete lining segments has been nominated for the Federal Patent Award 2018 of the Austrian Patent Office.

Related publications
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Lienhart W, Buchmayer F, Klug F, Monsberger C (2019) Distributed Fiber Optic Sensing on a Large Tunnel Construction Site: Increased Safety, More Efficient Construction and Basis for Condition-Based Maintenance, Proc. International Conference on Smart Infrastructure and Construction 2019: 595–604. This paper received the Best Paper Award (ICSIC). PDF

Monsberger C, Lienhart W, Moritz B (2018) In-situ assessment of strain behaviour inside tunnel linings using distributed fibre optic sensors, Geomechanics and Tunnelling 11 (2018), No. 6: 701–709. DOI

Henzinger R, Schachinger T, Lienhart W, Buchmayer F, Weilinger W, Stefaner R, Haberler-Weber M, Haller E-M, Steiner M, Schubert W (2018) Fibre-optic supported measurement methods for monitoring rock pressure, Geomechanics and Tunnelling 11 (2018), No. 3: 251–263. DOI

Monsberger C, Lienhart W, Kluckner A, Wagner L, Schubert W (2018) Continuous strain measurements in a shotcrete tunnel lining using distributed fiber optic sensing, Proc. 9th European Workshop on Structural Health Monitoring (EWSHM), Manchester, United Kingdom: 13 p. PDF

Monsberger, C. und Lienhart, W. (2017): In-situ Deformation Monitoring of Tunnel Segments using High-resolution Distributed Fibre Optic Sensing. 8th International Conference on Structural Health Monitoring (SHMII-8), Brisbane, Australien, 12 p. PDF

Gehwolf, P. & Monsberger, C. & Barwart, S. & Wenighofer, R. & Galler, R. & Lienhart, W. & Harberler-Weber, M. & Moritz, B. & Barwart, C. & Lange, A. 2016, ‘Deformation measurements of tunnel segments at a newly developed test rig’, Geomechanics and Tunnelling, vol. 9, no. 3, pp. 180-187. Reprint

Lienhart, W. und Galler, R. (2014): Tübbingelement mit Dehnungsmessung. Patent AT516158 (B1), filed 10.10.2014, granted 15.03.2016. PDF

Partners
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Acknowledgements
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The projects are funded by the Austrian Federal Railways and the Austrian Research Promotion Agency (FFG)