The Experimental Study of the Flow Pattern and Bed Topography Changes due to Variations in the Angle of the Gabion Spur Dike in the Open Channel with Erodible Bed

• Main Authors: Zainab Badpa, Majid Fazli, Sedighe Pazin
• Format: Article
• Language: fas
• Published: Shahid Chamran University of Ahvaz 2019-12-01
• Series: علوم و مهندسی آبیاری
• Subjects: gabion spur dike; flow pattern; bed topography; angle of spur dike
• Online Access: http://jise.scu.ac.ir/article_14324_e87c85aa6b8b03584bca4c1a89365f55.pdf

The construction of structures such as spur dikes in open channels and rivers is done to control the coastal erosion or water guidance and diversion. Scouring due to changes in the pattern of flow around the structure may result in instability and structural insufficiency, and if designed improperly, it may lead to complete degradation. Thus, the flow pattern and scour depth around the spur dike should be carefully considered. In effect, the type of spur dike used in each project, depending on its usage in the flow path, the depth of scouring and economic considerations must be carefully selected. The open gabion spur dike is one of the most affordable ones and is of high quality in terms of efficiency and ease of construction. <br /> A lot of research has been already conducted on impervious and angled spur dikes, including that of Ezzeldin et al.. In their research, they performed experiments on a blade spur dike at various angles ( 30,60 and 90 degree)  and reported that the spur dike at 30 degrees was best  in terms of depth of scouring and coastal protection. The maximum scour areas for the spur dike in their research were 90 and 60 degrees upstream of the spur dike, while the maximum scour area for the spur dike is 30 degrees along the length of the spur dike. Moreover, scour at 90 ° and 60 ° was equal, and in some cases higher scouring at a 60 ° angle and an increasing cost of constructing the spur dike in angular mode (Because of the real length of more in equal terms). The use of this type of spur dike was unrealistic at an angle of 60 degrees. In addition, Nagy (2005) showed a time test for the vertical and attracting spur dikes, as the scour rate for larger Froude number was higher, and the scour rate for the vertical state was greater than the attracting state. He further concluded that the angled spur dike had less scour depth and volume. Conducting experiments on the scouring around a trapezoidal spur dike at three angles to the downstream of the adjoining coast in two constricted ratios of 0.25 and 1.05, Kuhnle (2002) concluded that the 45 degree spur dike created the most scouring in the area adjacent to the coast, while less scouring was observed for the spur dikes of 90 and 135 degrees .