Experimental Study of the Effect of Permeability Percentage of Bandal Like Spur Dike on Maximum Depth of Scour Hole

Bandal like structures are used in the Indian Sub-Continent like Bangladesh as a local structure to maintain the navigability of the channel in alluvial rivers. This structure is a new type of spur dike with is made as a combination of permeable and impermeable spur dike. Local scouring in the nose of this structure is a designing problem of it that happens because of section constriction and strong vortexes. So determination of scour depth in designing of this structure is very important. There are few researches on Bandal Like spur dike, so in this research effect of spur dike permeability on maximum depth of scour hole around it was investigated. The experiments were conducted clear water conditions with the main variables of permeability percentage (4 cases) and four different discharges. For all experiments the spur length (L) and spurs relative spacing (S/L) were kept constant as 20% of the flume width and 3, respectively. The results showed that the maximum scour hole depth for the impermeable spur was much higher than that for Bandal Like. The minimum and maximum reductions on relative scour depth for Bandal Like spurs in comparison with the impermeable spur were calculated as 34.16% for permeability of 30%, at Froud-Number of 0.24 and 94.82% for permeability of 64%, at Froud-Number of 0.18, respectively.