Author(s): Sayed Hashmat Sadat; Akihiro Tominaga; Feng Cai
Linked Author(s): Akihiro Tominaga
Keywords: Spur dike group; Protective pile group; Erosion; Deposition; Flow structure
Abstract: Bed deformation characteristics and flow structure induced by spur dikes with and without protection in an open channel were investigated. The purpose is to study the effects of protective pile group as a measure to train the flow gradually and reduce the excessive local scour in the proximity of the spur dike under emerged condition. Efficiency of the number of pile-rows installed at the adjacent upstream of the first spur dike normal to the flow, and the disadvantages of the prototype models are remarked in this paper. As a result of clear water scouring process, the bed in the proximity of the prototype model was scoured tremendously, whereas installation of a number of pile-rows decreased the scouring hole and depth significantly. By increasing the number of pile-rows from one row to four rows, the scour depth was increased accordingly, but not as much as in prototype case. However deposition of the sediment in the spur-dike field was larger in the cases with number of pile-rows, not maximum, nor minimum, but in the middle. In the prototype case, the sediments in the spur-dike field was excavated by combined effect of flow circulation there and excessive bed deepening at the spur-dike tip and spur-dike field front areas. Flow velocity in the vicinity of the first spur dike and in the spur-dike field was decelerated by the interactions of pile-rows with the flow before passing the spur-dike. Most of the bed deformation characteristics manifested themselves in depth-averaged velocity distributions and estimated shear stresses near the bed.
Year: 2013