Scour was responsible for most of the U.S. bridges that collapsed during the past 40 years. The maximum scour depth is the most critical parameter in bridge design and maintenance. Due to scouring and refilling of riverbed deposits, existing technologies face a challenge in measuring the maximum scour depth during a strong flood. In this study, a new methodology is proposed for real-time scour monitoring of bridges. Smart rocks with embedded objects and/or electronics are deployed around the foundation of a bridge as field agents. With wireless communications, these sensors can send their position information to the mobile station near the bridge. This paper focuses on the design and characterization of passive and active sensors. The passive sensors use permanent magnets and their strengths are measured with a G858 magnetometer. The active sensors use either reconfigurable magnets with external power or accelerometers/magnetometers with a magneto-inductive communication system. Specifically, the signal strength of various permanent magnets will be quantified to understand their maximum measurement distance; the final design and test of a small-scale magneto-inductive communication system with small smart rocks are presented; and the acoustic communication protocol and implementation are evaluated.
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