Fundamental experiments on the establishment of a method for monitoring failure of river levees using DAS technology

Abstract

The applicability of DAS (Distributed Acoustic Sensing), a vibration-type optical fiber measurement method for detecting the soil particle movement accompanied with seepage flow in a river embankment and deformations caused by erosion of the embankment due to overflow, was verified in laboratory experiments. First, the characteristics of vibration waveforms during soil particle movement were investigated from elemental experiments using a small soil tank, and then the elongation of optical fiber caused by soil particle movement was calculated from the vibration waveforms after waterlogging using a large embankment model with a full cross section of the embankment in an overflow break test. As a result, it was found that the vibration waveform measured by the DAS could be regarded as a single-amplitude spike waveform, i.e., the amount of displacement of the optical fiber cable elongation, and that this displacement occurred within a short period of 5 to 10 ms.