Local scour is the removal of soil around bridge foundations under the erosive action\nof flowing water. This hydraulic risk has raised awareness of the need for developing continuous\nmonitoring techniques to estimate scour depth around bridge piers and abutments. One of the\nemerging techniques is based on monitoring the vibration frequency of either bridge piers or a\ndriven sensor in the riverbed. The sensor proposed in this study falls into the second category. Some\nunresolved issues are investigated: the effect of the geometry and material of the sensor, the effect of\nthe embedded length and the effect of soil type. To this end, extensive laboratory tests are performed\nusing rods of different materials, with various geometries and lengths. These tests are conducted\nin both dry sand and a soft clayey soil. Since the sensor will be placed in the riverbed, it is crucial\nto evaluate the effect of immersed conditions on its response. A numerical 3D finite-element model\nwas developed and compared against experimental data. This model was then used to compute\nthe â??wetâ?? frequencies of the sensor. Finally, based on both the experimental and numerical results,\nan equivalent cantilever model is proposed to correlate the variation of the frequency of the sensor to\nthe scour depth.
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