Local scour and riprap stability at an abutment in a degrading bed

Dey, Subhasish ; Chiew, Yee-Meng ; Kadam, Mahadev Shrirang (2008) Local scour and riprap stability at an abutment in a degrading bed Journal of Hydraulic Engineering, 134 (10). pp. 1496-1502. ISSN 0733-9429

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Official URL: http://ascelibrary.org/hyo/resource/1/jhend8/v134/...

Related URL: http://dx.doi.org/10.1061/(ASCE)0733-9429


The paper reports on an experimental investigation concerning two important issues: (1) local scour and (2) riprap stability at a 45° wing-wall abutment in a degrading river bed of noncohesive sediment. The abutment considered was short (that is abutment length/flow depth < 1). From the experimental observations, no influence of abutment inclusion on bed degradation was evident, as bed profiles with and without abutment were quite identical apart from the immediate vicinity of the abutment. Total scour depth at an abutment is found to be the maximum abutment scour depth in addition to the reduction of bed elevation due to bed degradation. The maximum abutment scour depth can be estimated from the equation given by Kandasamy and Melville in their 1998 paper. For scouring time beyond 24 h, the local abutment scour depth remains independent of time. In a degrading bed, the bed forms cause edge failure of the riprap at an abutment when the dunes propagate over the riprap layer. Initially, the dune height is significant causing the maximum damage of riprap layer. As the flow velocity reduces, the resulting bed-shear stress diminishes with the degrading bed and gradually the formation of dunes ceases. An additional experiment reveals that the damaged riprap layer is significantly vulnerable against a subsequent flood accompanied by large dunes.

Item Type:Article
Source:Copyright of this article belongs to American Society of Civil Engineers.
Keywords:Abutments; Degradation; Erosion; Scour; Riprap; Streambeds
ID Code:78820
Deposited On:23 Jan 2012 04:01
Last Modified:23 Jan 2012 04:01

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