SCOUR DEPTH MEASUREMENT AROUND PIERS OF AL HINDIYA SECOND BRIDGE

Local scour is the erosion of natural bed material around bridge piers by the vortexes action offlowing water. It can result in structural collapse, loss of life and property. Local scour is livebedif the flow upstream bridge is transporting bed material, otherwise it is clear water. In thispaper, the local scour around the piers of al-Hindiya second bridge during the year 2013 wasstudied. From field surveys at the bridge site it was observed that the cross section area of riverupstream bridge is concentrated to the left side as a result of the presence of middle bar. Alsothere is a scour hole with depth about 4 m around the 4th pier from left bank of the river, while noscour effect was found at the other piers. The field scour depth was compared with depthcalculated from the seven empirical equations using bridge geometry, bed materials propertiesand hydraulic characteristics of the stream flow at approach channel. Laursenꞌs equation wasused to find critical velocity of bed materials which showed that there was clear water scouraround bridge piers and the scour formula by Sheppard Melville 2006 had a good agreementwith measured scour depth, while other equations were underestimation. Depending on Sheppardand Melville equation a new empirical formula was proposed for al-Hindiya second bridge topredicate the scour depth around the pier corresponding to the hydraulic conditions similar as thestudy region.