Abstract
Scour induced by currents is one of the main causes of the bridge failure in rivers. Fundamental knowledge and mechanisms on scour processes due to currents are often taken as a basis for scour studies, which are the focus of this review. Scour development induced by waves and in combined wave–current conditions are also briefly discussed. For the design of structure foundations, the maximum scour depths need to be estimated. The mechanisms of local scour and predictions of maximum local scour depths have been studied extensively for many years. Despite the complexity of the scour process, a lot of satisfying results and progresses have been achieved by many investigators. In order to get a comprehensive review of local scour for vertical piles, major progresses made by researchers are summarized in this review. In particular, maximum scour depth influencing factors including flow intensity, sediments, pile parameters and time are analyzed with experimental data. A few empirical equations referring to temporary scour depth and maximum scour depth were classified with their expressing forms. Finally, conclusions and future research directions are addressed.
Highlights
In river hydraulics, bridge failures due to local scour occurred frequently
This paper reviewed and studied conditions of steady currents, circular and square cross vertical piles, non-cohesive sediments and perpendicular flow angle attacks
For non-uniform scour, Chang et al [76] conducted a series of tests, finding that the equilibrium time and the maximum scour depth decreased with σg
Summary
Bridge failures due to local scour occurred frequently. In the U.S, a large amount of bridges are vulnerable to scour, and many of them are being scoured critically. Local scour around vertical piles in steady currents have been studied for a long time It was divided into clear-water scour and live-bed scour by Chabert and Engeldinger [5]. Zanke et al [29] have developed an empirically based prediction approach by introducing a new function between the wave and current generated scour at a singular pile Based on these laws, Miozzi et al [30] conducted an experimental test with KC = 10. Laws for flow field around the pile, including velocity and pressure distributions in three dimensions, characteristics of horseshoe vortex and vortices shedding, boundary layer and shear stress near the bed were successfully obtained by scholars [6,10,17,21,23]. The empirical equations are summarized and classified into four expressing forms
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