Kumcu S.Y.,University of Konya |
Kokpinar M.A.,State Hydraulic Works DSI |
Gogus M.,Middle East Technical University
KSCE Journal of Civil Engineering | Year: 2014
The cause of local scour around a bridge abutment is mainly the presence of spiraling vortex flow structure called the principal vortex. A rigid surface around an abutment with a collar can arrest the growth of the vortex, and therefore, reduces the scour depths around the abutment compared to the case without a collar. This paper presents an experimental investigation related to the collars of different sizes placed around vertical-wall bridge abutments at various elevations in an erodible bed flume that consists of two different types of almost uniform sand of (d50)1 = 1.48 mm and (d50)2 = 0.90 mm to show the effect of collars on the scour depths around the abutments. A series of experiments were conducted at the laboratory under clear-water conditions at flow intensity of U/Uc = 0.90, where U is the average velocity of the approach flow and Uc is the critical flow velocity for the sediment motion. The maximum scour depths forming around the abutments were determined at the end of each experiment conducted with and without collar for a time period of 6 hours. Experimental results showed that, a collar placed on the abutment at or below the bed level is able to reduce the maximum scour depth around the abutment by 70-100% as a function of the collar and abutment sizes in comparison to that of an unprotected abutment. The optimum location of a collar on a vertical-wall abutment, which will result in the maximum percentage reduction in the maximum scour depth, is generally below the bed level and can be expressed as a function of the dimensionless abutment length and collar width. It was also observed that although the abutment itself was protected, the collars of larger sizes shift the scour region away towards downstream from the abutment, with scour depths smaller than the maximum scour depth at the abutment for the case of no collar. The experimental observations and analysis presented in this study established that the optimum dimensionless location of the collar on the abutment which yields the maximum scour reduction was not affected by the sediment having finer diameter. Therefore, abutment-collar arrangements could be an appropriate alternative solution to riprap protection that is widely used in practice in countering scour problems at bridge abutments. © 2014 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Apaydin A.,State Hydraulic Works DSI
Water International | Year: 2011
The uneven distribution of water resources, a growing population, urbanization and global climate change require new approaches for groundwater management in Turkey. "Safe yield" should yield to broader concepts such as "sustainability". Groundwater management needs to consider future needs of the people and all ecosystems in accordance with basin development models. Groundwater law needs to be expanded beyond quantity to address quality concerns. A new institutional framework should be established and groundwater regulation should reflect new approaches and ideas, in particular to address problems of application. © 2011 International Water Resources Association.