oa Crack Detection using DAS for Concrete Structures

We propose a crack detection method to simplify the visual crack inspections on large concrete structures such as dams, tunnels, and bridges, which consume enormous amount of time and labor. The method uses Rayleigh waves attenuated by cracks, and it has been implemented in geophones but not in DAS. In this study, to demonstrate the applicability of DAS for crack detections, we measured and analyzed Rayleigh waves using DAS on a concrete slab with cracks. In the measured data, attenuation of Rayleigh waves was observed near cracks, suggesting that the cracks can be detectable. The measured results also show that the frequency of the attenuated Rayleigh waves depends on the depth of the crack. However, the attenuation and recovery of the waves unrelated to the cracks were observed, seemingly because reflected waves generated at the slab edges are mixed with surface waves, thus reducing the data quality. To apply this crack detection method to actual structures, further investigations is required into reflected waves generated at the edges of the structure, as well as the relationship between spatial resolution of interrogators and detectable crack depth.