In Vitro Evaluation of the Composition of Rectangular Panels Connected to the Beach and Horizontal Blade in Controlling Erosion of Convergent 90-Degree Arch

Abstract

On the river arch, the formation of secondary flow causes erosion in the outer bank and sedimentation in the inner bank. Sediment accumulation in downstream of arches causes decrease in the river width and therefore arces are mainly seen as convergent in nature. Controlling erosion in the outer bank of arches is done in various ways including the use of spur dike structures. In the rigid spur dike, the flow hitting to the structure body creates a downstream flow and causes aggravated scour around the spur dike; therefore, in order to solve and control this problem it is possible to install horizontal panels on spur dikes. In the this study, in ordr to investigate the effect of horizontal panels installed on the thalweg bed, by making a 90 degree convergent arched channel and installating 4 rectangular spur dike in the positions of 30, 45, 60 and 75 degrees in a way in which the panels occupied 15 percent of the channel width and installing horizontal panels with a length of 10 cm and a width appropriate to the spur dike in three positions of 3 cm above the bed, on the bed and 3 cm below the bed, and by considering the sandy bed thickness of 15 cm and the average diameter of sediment equal to 1.15 mm, a total of 15 tests were carried out in different conditions with three discharges. The results of this study showed that the spur dike are generally successful on the movement of the thalweg and installing horizontal panels causes aggravated thalweg, so that in installation conditions at different altitudes of scour depending on the flow conditions and Froude number the effectiveness of spur dike is different.