Effect of the Contraction ratio and the Shape of the Abutment on the Local Scour at a Bridge Abutments

Scour process at the abutment of bridge is influenced by the contraction of the stream flow specially when the abutment immure an effective width of the stream flow, also the shape of the abutment has an important effects on the scour depth at the abutment. In this paper a series of laboratory experiments were carried out to study the effect of contraction ratio and abutment shape on the scour and its maximum depth at the abutment. Three shapes of abutments with three-contraction ratio with different flow rates were used. The result of the experiments showed that the circular shape and (30) angle abutments reduce scour compared with that, which was, occur at the rectangular abutment. The reduction of scour depth with circular shape is about (22%) where that with (30) angle is about (27%), also a dimensionless general empirical formula was created for the calculation the scour depth by using the (SPSS 11.5) Statistical program a Coefficient (R=0.933) of determination.