Geotechnical monitoring at the speed of light: New insights from distributed acoustic sensing

Abstract

Recent advances in distributed fibre optic sensing enable new opportunities in geotechnical monitoring and characterization. Distributed acoustic sensing (DAS) is a distributed fibre optic sensing technology relying on Rayleigh backscattering of light to detect and locate disturbances in near real-time along tens of kilometres of fibre optic cable. The dynamic strain sensing capabilities of DAS have prompted numerous research initiatives from the seismology community over the past decade. Although research on DAS for seismic applications is well established, studies on DAS for geotechnical monitoring applications are less common. Here, we present a summary of two recent case studies involving DAS for geotechnical monitoring. The first study considers a slow-moving landslide where DAS data were acquired over a three-day period of rainfall. The DAS aseismic strain and strain-rate data support the interpretation of the triggering and retrogression failure mechanism of the landslide. The second study considers an active mine site in northern Canada. Data were acquired from a cable installed ~1m below a tailings dam crest. Passive seismic interferometry was applied to DAS data to infer changes in seismic velocities in the uppermost several meters of the subsurface. These findings represent a first step towards advancing continuous monitoring techniques with fiber optic sensing technologies. However, further research is needed to improve our understanding of DAS performance for geotechnical monitoring applications over longer-term periods.

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