Document Type : Research Article
Maximum scour depth around a series of spur dikes is one of the important problems in their design.
In this paper, the mitigation of scour depth around a series of consecutive spur dikes within a straight
reach was investigated by using a protective spur dike located upstream of the first main spur dike.
Effect of different parameters of protective spur dike is experimentally investigated including 4 ratios
of protective spur dike length to the first main spur dike length (Lp/Lf) equal to 0.2, 0.4, 0.6 and 0.8,
three angles of protective spur dike (B) of 45, 90 and 135 degree and 4 ratios of protective spur dike
distance to the first main spur dike length (X/Lf) equal to 1, 1.5, 2 and 2.5. The experiments were
conducted for the velocity of incipient motion for bed sediment movement and bed size diameter of
0.91 mm (D50) and standard deviation of 1.38. The effect of protective spur dike on the flow pattern
around the spur dikes was investigated in a rigid bed too. The experiments showed that the proper
design of protective spur dike can significantly mitigate maximum scour depth around the main spur
dikes. In particular, the protective spur dike with Lp/Lf =0.8, X/Lf=2, B=45° decreased an average of
76.6 percent of scour depth around the spur dikes. The maximum decrease of scour depth around the
first spur dike (74.7 percent) was obtained by applying the protective spur dike with Lp/Lf=0.8,