Experimental study of local scour around non-uniform twin piers

Abstract

ABSTRACT Prediction of scour at complex or non-uniform piers has been mostly aimed at single piers, while most bridges are constructed on a group of non-uniform piers. The novelty of this study is to investigate the effect of foundation level and piers’ distance on local scour around the non-uniform twin-piers. The experiments were carried out considering five foundation levels, under and above the bed, with various piers distances in clear-water conditions. Results show that for the case of foundation level above the bed, scour depth at non-uniform twin piers is larger than that of uniform configuration, and distance between piers has no significant influence on scour depth. For the case of foundation at bed level, the distance between piers has no remarkable effect on scour depth while the scour depth around non-uniform twin piers is found to be less than that of uniform ones. When the foundation is under the bed level, the presence of the foundation reduces the scour depth around both front and rear piers, and the distance between piers has a direct effect on the scour depth. In this zone, the foundation delays the scour process and the scour time increases with increasing foundation depth. This study highlights that a proper design of the foundation level increases the duration of scouring and decreases the scour depth.