الفهرس 
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Abstract
One of the main reasons for bridge failure is local scour at the bridge abutments. A number of laboratory experiments under clear-water scour conditions, were carried out to investigate scour reduction around the vertical bridge abutment (the reference) by using countermeasures which were spur dikes, parallel walls, and sacrificial piles. Analyzing the collected data was by Excel and the Surfer programs. Empirical equation for each set for estimating maximum scour depth, and general equations for each stage for estimating maximum scour depth and horizontal dimensionless of the scour hole were developed by nonlinear regression program SPSS. The countermeasures were shown as follows: The first stage, spur dike was used to study the effect of vertical spur dike location (Ds) on the scour at the abutment, where this stage contained six sets to find the best touched distance of the flume wall between abutment and spur dike (Ds), it`s evident that, Ds of 3L is the best set in this stage, where L = length of abutment therefore this set will be used as a constant parameter in the second and third stages. The second stage, before starting the second stage it is concluded that the best Ds = 3 L from the first stage. Spur dike was used to study the effect of spur dike orientation angle with respect to the abutment (θ) on the scour at the abutment, where the flow-perpendicular length of spur dike was fixed to be L = length of abutment, this stage included four sets to find the best (θ), it`s evident that, θ = 90° is the best set in the second stage therefore this set will be used as a constant parameter in the third stage. Also, it is mentioned earlier from the first stage that Ds = 3L will be used as a constant parameter in the third stage. The third stage, before starting the third stage it is concluded that the best Ds = 3 L from the first stage and the best θ = 90° from the second stage will be used as constant parameters in this stage. Spur dike was used to study the effect of spur dike projection length normal to flow direction (Lsp) on the scour at the abutment, this stage included three sets to find the best (Lsp), it`s evident that, Lsp =1.0 L is the best set in the third stage. from the above, it is concluded that using spur dike leads to a good reduction on scour depth at the abutment, where the set of spur dike [ Ds = 3 L, θ = 90°, Lsp =1.0 L] is the optimum set, with percentage of scour reduction is 81.56 %. The fourth stage, a vertical parallel wall was used to study the effect of a vertical parallel wall length (Lpw) on the scour at the abutment, where this stage contained five sets to find the best (Lpw), it is found that as length of parallel wall (Lpw) increases the relative scour depth (ds/y) decreases, where Lpw =1.2 L is the optimum set , with percentage of scour reduction is 61.24%. The fifth stage, sacrificial piles were used to study the effect of the set of single sacrificial pile and the set of number and arrangement of piles (n × m) on the scour at the abutment, where n = number of piles perpendicular to the flow, m = number of piles inline with flow. This stage contained four sets to find the best (n × m), where for all the sets the value of G (gap between abutment and pile, also between piles) is a constant = 4.0 cm, (G/L = 0.25), and also for all the sets, the value of D_p (diameter of pile) is a constant = 2.0 cm, (D_p/L = 0.125). It`s evident that a single sacrificial pile is the optimum set in the fifth stage with percentage of scour reduction is 25.07 %. While at using a pile group (n × m), it is evident that six sacrificial piles (2 × 3) is the optimum set in the pile group (n × m) with percentage of scour reduction is 24.35 %, where as the number of piles increases the relative scour depth (ds/y) decreases.