A Study on Interaction between Overfall Types and Scour at Bridge Piers with a Moving-Bed Experiment

Abstract

River slopes can be changed due to an extreme event, e.g., a large-scale earthquake. This can uplift a riverbed greatly and thereby change the behavior of the river flow into a free or submerged overfall. Corresponding damage, including extreme erosion, on bridge piers located in the river can take place due to the aforementioned flow conditions. A reconstructed bridge pier in the same location would also experience a similar impact if the flow condition is not changed. It is important to identify these phenomena and research the mechanism in the interaction between overfall types and scour at bridge piers. Therefore, this paper is aimed at studying a mechanism of free and submerged overfall flow impacts on bridge piers with different distances by a series of moving-bed experiments. The experiment results showed clearly that bridge pier protection requires attention particularly when the pier is located in the maximum scour hole induced by the submerged overfall due to the z directional flow eddies. In many other cases, such as when the location of the bridge pier was at the upstream slope of a scour hole induced by a flow drop, a deposition mound could be observed at the back of the pier. This indicates that, while a pier is at this location, an additional protection takes place on the bridge pier.

Near-Nature Ecological Technique for Pier Scour Countermeasure in a Submerged Overfall

“…The above pioneering work generated much scientific and engineering interest in the following years. Varied empirical formulas have been proposed for the estimation of local scour due to drop structures and bridge piers under different conditions of structure types, approach flow, and bed material [6][7][8][9][10][11][12][13][14][15]. Such contributions are important to effectively control overfall-induced scour and diminish the scour around piers, an area that is influenced by scour hole.…”

Soil–Water Conservation, Erosion and Landslide

“…Such a tool is crucial in watershed conservation, especially in a world generating enormous data that requires super-fast models. In another instance, Lee et al [21] evaluates seven machine learning models for time-saving to estimate the rainfall-erosivity factor (R-factor) used in the Universal Soil Loss Equation (USLE). Their findings show that deep neural networks are very efficient estimating the R-factor given monthly precipitation, maximum daily precipitation, and maximum hourly precipitation.…”

“…Finally, the article by Lee, Lu, and Huang [21] investigate the interaction between overfall types and scour at bridges. When a bridge pier is in the maximum scour location, it induces more scour due to disturbances caused by the water jet and the pier; hence, more attention is required to protect the pier.…”