Effect of abutment aspect ratio on clear‐water scour in floodplains

Abstract

AbstractScour around abutments is recognized as one of the main reasons of bridge foundations failure. This paper presents the experimental results of the effects of abutment width and length on the scour development up to its equilibrium condition around 45° wing‐wall setback abutments in a compound channel. The developing scour hole characteristics are tested for three different lengths and widths at different time intervals until its equilibrium scour conditions. The findings showed that the abutment width has a profound effect on the characteristics of the scour hole, contradicting the results of previous studies. Generally, an increase in the relative abutment width leads to a reduction in the scour depth and width. However, the scour length, area, and volume initially increase with an increase in the relative abutment width, Lc/yf, from 1.33 to 10.67, where Lc is the abutment width and yf is the floodplain flow depth, and then these characteristics decrease significantly with a much wider abutment, Lc/yf, from 10.67 to 21.33. Overall, the effects of the abutment width on abutment scour should be accounted. To this end, empirical equations are proposed to predict the scour hole characteristics. Scour data from previous studies are also used to compare with the proposed equations.