On the use of high-resolution distributed Fibre optic sensing for small-scale geotechnical tests at 1g
The use of distributed fibre optic sensing (DFOS) is becoming increasingly popular for strain measuring and monitoring. While the technology is efficient in the field, its use for strain measurement in geotechnical model-scale experiments is currently limited, mostly because of a lack of spatial resolution in the DFOS technologies. However, recent developments now enable high spatial resolution measurements, for example, with the use of Rayleigh Scattering technology for the fibre and the Luna ODiSI 6100 DFOS analyser. This technology is becoming increasingly popular for use in small-scale experiments, mainly for structural monitoring. For geotechnical applications, there are a few technological barriers that presently limit their use in the laboratory. However, there are great advantages in using this technology, mainly to measure strain deformation continuously along the fibre at the core of a soil sample. This paper explores the possibility of using high-resolution distributed fibre optic sensing for small-scale geotechnical experiments at 1g, using a trapdoor rig that mimics the formation of a sinkhole. The fibre optic is embedded in the soil above the trapdoor to measure subsidence, and different laying techniques are explored, aiming at enhancing the coupling between the fibre optic cable and the surrounding soil at low confining pressures. This work aims at widening the range of instrumentation available to measure strain in small-scale geotechnical experiments, offering a complementary technique to conventional instrumentations.