الفهرس 
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Abstract
It is observed that the major reason for bridge’s damage or collapse are those related to the scouring at bridge piers and abutments but 25% of the failures included piers damage while 75% involved abutments scour. Hence, in this thesis scour around bridge abutments is studied experimentally in the laboratory of Irrigation and Hydraulics, Faculty of Engineering, Mansoura University- Egypt. A total number of ninety-six runs were conducted to simulate local scour around various abutment shapes in non-uniform sediments under clear water scour conditions. Four hours were chosen as a test duration after doing the preliminary tests because it was observed that the difference between the scour depth after four hours and after seven hours is less than 1 mm. Thus, it can be considered that the equilibrium depth of scour occurs after four hours. The maximum scour depth is evaluated at the end of each experiment also, contour nets are taken to analyse the data. In this research a comparison between different shapes of abutment were carried out as vertical abutment, semicircular ended abutment, abutment with vertical sloped face, and wing wall abutment. Also, the influence of pile existence to reduce the maximum scour depth was investigated. For vertical abutment, it was observed that the width change affect slightly on the scour depth. For semicircular ended abutment, the increase of the radius of curvature (𝑅) leads to decrease scour depth. In case of abutment with vertical sloped face, it was proved that the increase of side slope angel (θ) leads to reduce scour depth. For wing wall abutment, it was proved that the decrease of wall angel (∝) leads to reduce scour depth. The results indicated that wing wall abutment with ∝=60° gave the minimum scour depth compared with the other studied abutment shapes. It minimized the maximum scour depth by 22.68% compared with vertical abutment. Also pile existence with (Dp/B=0.08, X/B=0.25) reduced the maximum scour depth by 22% compared with no pile case. For all abutment shapes, it is observed that when the Froude number increases the maximum scour depth increases. Furthermore, empirical relations were derived to predict the maximum scour depth for the studied types of abutment shapes using SPSS programme.