Recent Experiences with Optical Fibre Monitoring of Geotechnical Structures-Paper

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The paper reviews optical fibre (OF) monitoring of geotechnical structures, drawing on projects conducted by the Belgian Building Research Institute since 2007. Monitoring supports design optimisation, construction quality control, long-term performance assessment, maintenance planning, and early warning.<br /><br />OF sensors measure strain and temperature using compact fibres that can provide dense readings over long distances. They are resistant to electromagnetic interference and harsh conditions, and require relatively little wiring. The main approaches are multipoint Fibre Bragg Gratings (FBG), which use sensors at selected locations, and distributed methods such as BOFDA, which use the entire fibre as a sensor. Each involves trade-offs in accuracy, spatial resolution, measurement speed, and equipment and cable cost. Strain readings often require temperature compensation, and careful installation is essential because fibres and splices can be fragile.<br /><br />Case studies demonstrate OF monitoring in diaphragm walls, grouted anchors, foundation piles, micropiles, geothermal boreholes, and energy piles. Measurements captured load distribution, shaft friction, base resistance, concrete temperature during placement and curing, soil thermal properties, and structural responses to combined mechanical and thermal loading. In pile testing, combining FBG and BOFDA provided complementary data and redundancy, though some fibres were damaged during installation or testing.<br /><br />Overall, OF sensing can achieve performance comparable to conventional instruments while offering high sensor density, compact installation, and long-term stability. Successful application depends on selecting the appropriate technology for the project’s measurement requirements and protecting the instrumentation during construction.

Keywords

optical fibre monitoring

geotechnical structures

Fibre Bragg Gratings

BOFDA

strain measurement

temperature compensation

foundation piles

micropiles

energy piles

distributed sensing