Local Scour at Complex Bridge Piers in Close Proximity under Clear-Water and Live-Bed Flow Regime

Abstract

In this study, we investigated the characteristics of scour at complex bridge piers in close proximity. The experiments were performed under both clear-water and live-bed flow regimes. We compare our results with those for a single complex pier. Further, the performance of existing predictors is discussed. In this study, four typical pier arrangements were adopted, including side-by-side with aligned or 30 • skewed flow, staggered, and tandem. The results show that the skew angle for a side-by-side arrangement significantly accelerates the clear-water scour development at all the vertical piles as well as between the piers, and the most scoured pile shifts from the upstream end to the downstream end of the upstream pier flank. The staggered and tandem pier arrangement show significant protection to the downstream pier for both the developing rate and the equilibrium scour depth. When the flow velocity exceeds the threshold for general bed motion, the clear-water scour pattern for all the pier arrangements may be altered significantly due to the upstream sediment supply, the weakened protection effect, and the enhanced flow contraction. The bed-forms migrate via the bridge opening and are damped gradually by the flow, and thus the response of the bed morphology under live-bed conditions is quite unsteady.

Scour at Bridge Piers Protected by the Riprap Sloping Structure: A Review

“…This leads us to the conclusion that in estimating scour depth, the component of flow area reduction should be considered in addition to local scour. Similarly, Yang et al [106] found that for complex bridge piers in close proximity, the upstream pier significantly affects scouring at the downstream pier in comparison to individual piers, reducing scour rate for clear-water conditions and increasing the bedform celerity for live-bed conditions.…”

Numerical Study of Road Embankment Type Action on Shear Stress Around Skewed Bridge Abutment

“…The best form of the piers, the smallest scouring around it, was the rhombus 30°, rhombus 60°, oblong and cylindrical, respectively. In another experiment, Yang et al (2019) studied typical piers in both common and skewed piers to the flow. They found that the skewed piers increased the scouring rate around the piers significantly.…”

Experimental Investigation of Local Scour Around Artificial Reefs in Steady Currents

“…The seabed looks 'alive', referred to as 'lived bed scour' (Chiew, 1984;Yang et al, 2019). Here, the critical velocity of the current, i.e., the velocity causing the critical shear stress of seabed, should be considered in the scour experiments (Liu et al, 2018).…”