Experimental Study of the Effect of Spur Dike Permeability and Angle on Scour Hole Dimensions in Non-Submerged Conditions

Spur dike is a hydraulic structure which has an essential role in reducing the shear force on river banks. The interaction between the structure and flow makes vertical and horizontal vortices, which are the main reason for producing a local scour hole around spur dike and finally damaging it. The  behavior of the flow around a spur dike and the intensity of degradation and aggradation depend on different factors such as the type of the spur dike, its position, its angle with the bank, and some other  parameters. One of the most important factors is the permeability of the spur dike. This experimental study focuses on the effect of spur dike’s angle and its permeability on scour hole dimensions in non-submerged conditions. According to the results, when permeability increased up to 50%, scouring  decreased  significantly. For Fr=0.24, and in the vertical  position of spur dike (90 degrees) with 50% permeability, relative depth, length, and width of  the scour hole decreased 67%, 75.3% and 45.5%,   respectively in comparison with impermeable spur dike. Also for the angle of 120 degrees, relative depth, length and width of the scour hole declined 64.1%, 72.1% and 35.4%, respectively. Similar results were obtained for the angle of 60 degrees with the reduction of relative depth, length  and width of the scour hole being measured  60.2%, 68.7% and 38.8%, respectively. In addition, for 50% permeability, the highest level of scouring was for the angle of 60 degrees, whose average relative depth, length, and width were 0.19, 0.7 and 1.2, respectively.