Author(s): Pietro Giaretta; Paolo Salandin
Linked Author(s): Pietro Giaretta
Keywords: Existing bridges; Local scour; Sonar sensor monitoring; Laboratory experiments
Abstract: The functionality of a river crossing must be ensured not only under normal conditions but especially during hazardous events, e. g. floods, when the efficiency of the infrastructure becomes fundamental to ensure the mobility of the rescue teams and the evacuation of the inhabitants. However, this is not currently accomplished, so that hydraulic phenomena account for over 50% of bridge failures. Among the hydraulic causes, the localized erosion at bridge piers that mainly develops during flood events plays a relevant role, also because it cannot be recognized or detected through a simple visual inspection. This study explores the ability of sonar sensors to continuously monitor the scour evolution investigating sensor measurements in several locations around different piers and comparing the monitoring results with maximum scour depths obtained by photogrammetric surveys. Laboratory experiments have been developed in a 1 m-wide flume using nearly uniform sand to simulate riverbed conditions. The scour around an elongated pier on rectangular foundation for the cases aligned and tilted respect the flow direction was simulated. In the first case the top of the foundation protrudes above the riverbed, while it is aligned with the riverbed in the second case. The results, obtained in clear water conditions, show that sonar sensors can effectively monitor along their vertical the scour evolution over time. The pier-foundation system parallel to the flow direction results in reduced scour depths compared to the tilted one even if in the former the top of the foundation is exposed respect to the riverbed. Anyway, in all the examined cases, the continuous monitoring data are consistent with the photogrammetric survey of the scour developed at fixed time. Moreover, the concurrent use of more sensors shows that is possible to acknowledge a critical condition even if their placement does not correspond to the one where the maximum scour depth develops. From the developed experiments, the effectiveness of the sonar sensor to acknowledge maximum scour depths can be deduced.
DOI: https://doi.org/10.64697/978-90-835589-7-4_41WC-P1841-cd
Year: 2025