Abstract
To reduce the local scour around bridge piers and ensure their safety, an experimental study was conducted to examine the effect of a single tubular hole that faces the flow direction through three successive cylindrical bridge piers. In order to reduce the local scour, occurred because of the collision of the flux. Two groups of successive piers were used, both had diameters of 5, 11, 16 cm. First group of piers with internal tubular opening which had 20% diameter of the pier and located at half the water depth. The second group just solid pier for comparison. The spacing between them was varied to be 30, 40 or 50 cm for each group. As well as the discharge was varied. The used moveable bed material classified as non-uniform coarse sand, which had 0.5 mm mean diameter. The results showed that the presence of the openings helps effectively to reduce the depth of scour and its effect increases as the diameter of the opening increases, as the highest reduction reaches 55.56%, 53.33% and 10% for diameters 16, 11 and 5 cm, respectively. The scour depth increases when the diameter of the pier the increase of and the short distance between the successive piers.
