Experimental Investigation the Effect of Geometry Parameters of Straight and T Shape Gabion Groynes on Local Scouring

AbstractOne of the usual methods for river banks protection is using Gabion groyne structures. A local scouring phenomenon is one of the important problems in hydraulic design of groynes. Due to constriction and downward flow، the scouring can occur around the groynes. In this investigation a laboratory movable bed flume with 18m length، 1. 5m width and 0. 8m depth was used. To study local scour near the head of unsubmerged Gabion groynes، the groynes were constructed perpendicular to the flume''s wall. Two shapes of groyne (straight and T shape)، two constriction ratios (20% and 30%) and four ratios of space to length (S/L)، were used with one constant bed material and one constant bed slope with three different discharge. Based on the experiment results، for straight S/L=3 and for T shape S/L=4 is recommended the suitable S/L ratios. Regarding the type and shape of groyne، T shape groyne indicated the least scouring and the scouring depth of Gabion groyne was less than of impermeable groyne.