An Experimental Study of Impact of Bridge Pier on Depth of Scour Hole in Abutment

Many of bridge piers have been located in the vicinity of abutment and bridge supports. Local scour at the abutment nose is considered as one of the major factors in designing the abutments. The presence of bridge piers in the vicinity of abutments can affect the scour rate of them, due to the creation of strong vortex flows between piers and abutment. Hence, this study investigates the impact of single bridge piers on the depth of scour hole in the abutment, experimentally. For this, in the first case, a single bridge pier and an abutment, and in the second, two tandem bridge piers and an abutment, were placed in the experimental channel. The piers and abutment were established at three different distances (X), so that they can satisfy the constrain !" #$ = 3.5, (D: pier diameter, x: distance between pier and abutment). Results showed that in the second case study i.e. [two tandem bridge piers and an abutment], presence of piers in most of experiments increased the scour depth in abutment. In the case of using single pier, the effect of pier on abutment scour depth is either negligible or decreasing. Generally, when the pier's diameter was about 50 percent of abutment's length, the minimum depth of scour was reached, and when the diameter of pier was bigger than abutment's length, maximum depth of scour in abutment was obtained.