Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

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.

Scour Hole Development in Natural Cohesive Bed Sediment around Cylinder-Shaped Piers Subjected to Varying Sequential Flow Events

“…For example, similar maximum scour depths for both non-cohesive and cohesive sediments under similar flow conditions have been reported [5,7]. Other studies have reported lower or even higher maximum scour depths for cohesive soils compared to non-cohesive soils [8,9,[24][25][26][27][28].…”

“…The influence of time dependency of scour development in non-cohesive sediment have been considered in numerous studies [24][25][26][27]. Several studies have also investigated the influence of flow duration, flow magnitude, and flow frequency on erosion behavior of cohesive soil, including the influence on bank erosion, fluvial erosion (channel incision), and localized scour around structures [28][29][30][31].…”

Lithological control on scour hole formation in the Rhine-Meuse Estuary

“…Various factors likely contribute. Firstly, the causes that trigger scour hole formation include turbulent flows induced by river bends (e.g., Engelund, 1974;Zimmermann and Kennedy, 1978;Odgaard, 1981;Andrle, 1994;Gharabaghi et al, 2007;Blanckaert, 2010;Beltaos et al, 2011;Ottevanger et al, 2012;Vermeulen et al, 2015), confluences (e.g., Mosley, 1976;Kjerfve et al, 1979;Best, 1986;Ginsberg and Perillo, 1999;Pierini et al, 2005;Best and Rhoads, 2008;Ginsberg et al, 2009;Ferrarin et al, 2018), local channel narrowings and structures, like bridge piers, groynes and bed protection (e.g., Wang et al, 2017;Pandey et al, 2018;Liang et al, 2020). These types of scour holes evolve differently, have different shapes, and as a result have different relations for predicting their equilibrium depth (Hoffmans and Verheij, 1997).…”

“…With their steep slopes and large depths, these scour holes can threaten the stability of nearby infrastructure like embankments, bridge piers, tunnels and pipelines (e.g. Gharabaghi et al, 2007;Beltaos et al, 2011;Wang et al, 2017;Pandey et al, 2018;Liang et al, 2020). The formation and development of local scour, bend scour, and confluence scour are widely studied (e.g., Engelund, 1974;Mosley, 1976;Zimmermann and Kennedy, 1978;Kjerfve et al, 1979;Odgaard, 1981;Best, 1986;Andrle, 1994;Ginsberg and Perillo, 1999;Pierini et al, 2005;Gharabaghi et al, 2007;Best and Rhoads, 2008;Blanckaert, 2010;Beltaos et al, 2011;Ottevanger et al, 2012;Vermeulen et al, 2015;Wang et al, 2017;Ferrarin et al, 2018;Pandey et al, 2018;Liang et al, 2020).…”

Using Artificial-Reef Knowledge to Enhance the Ecological Function of Offshore Wind Turbine Foundations: Implications for Fish Abundance and Diversity

“…The material is placed around the foundation of the turbine (e.g., around the monopile) with a radius typically reaching up to 20 m [34,35]. The size and design of the scour protection is determined by a range of environmental factors (i.e., wave and current activity, water depth, sediment characteristics), as well as structural factors (i.e., monopile diameter and design) [36,37] (Figure 1). Generally, the size of the scour protection area reflects the area of the scour pit that would arise due to the environmental factors (e.g., current speed), if the foundation was left unprotected [31], which is usually four to five times the monopile diameter [38].…”