Abstract

Sinkholes are a geo-hazard, which can form suddenly without obvious pre-indication from soil surface settlement, and can induce severe damages to infrastructures or loss of human lives. Monitoring the soil deformations would enable to minimize or avoid possible damage. This work explores the possibility of using Distributed Fibre Optic Sensors (DFOS) as a solution for early warning detection of sinkhole formation, with the main objective directed towards proving the effectiveness of this technology in reading soil induced strains. Sinkholes were simulated using trapdoor tests at 1g in controlled condition, and soil movements were recorded using PIV analysis. Three layers of Fibre Optic cables were laid within the specimen at different depths, and analysed with the LUNA O DiSI 6100 analyser. The tests show the ability of the DFOS in detecting soil movements and underline the typical signature strain profile expected during sinkhole formation. The magnitude of strains observed along the cables are lower compared with the results of PIV . In order to understand this discrepancy, 3D FE analyses were carried out to study the behaviour of the cable within the soil mass. Numerical results are in agreement with the experimental data and show that horizontal movements govern the strain profile within the cable, proving that the soil-cable interface plays a crucial role.