GRS Abutment Study: Interaction between Riprap Countermeasures and Contraction Scour
Abstract
This research study presents findings from abutment clear-water experiments on erodible uniform bed material and Computational Fluid Dynamics (CFD) composite roughness models used to investigate distribution of flow velocity, unit discharge, and boundary shear stress associated with different riprap installation geometries based on field installations and design guidelines from HEC23. The data apply for the case of bridges crossing narrow river channels and vertical-wall GRS abutments extending into the main channel. CFD composite roughness models with different riprap geometries show how abutment flow fields, dominated by flow contraction around the abutment, adjust in response to variations of bed roughness and cross-section geometry due to riprap placement. These adjustments increase the magnitudes of bed shear stress on the unprotected channel bed leading to underestimated contraction scour depths. Consequently, the increase in erosion of the unprotected bed may undermine the riprap mattress creating instability, and ultimately causing edge failure of the countermeasure around the abutment. A preliminary relationship for the maximum contraction scour depth is suggested to illustrate the riprap installation geometry and bed roughness effects on contraction scour for bridges crossing narrow waterways. The proposed relationship is limited to the range of values covered by the variables in this study.
How to Cite:
Suaznabar, O. & Xie, Z. & Kerenyi, K., (2014) “GRS Abutment Study: Interaction between Riprap Countermeasures and Contraction Scour”, National Hydraulic Engineering Conference 2014 1(2014).
Rights: Copyright © 2014, Oscar Suaznabar, Zhaoding Xie, and Kornel Kerenyi
Publisher Notes
- Panel moderated by Dave Claman, IOWADOT.
- About the Presenters: Oscar Suaznabar is a Research Hydraulic Engineer at Genex Systems with base at the FHWA Turner-Fairbank Highway Research Center (TFHRC) J. Sterling Jones Hydraulics Laboratory in McLean, VA. He holds a M.Sc. in Water Resources Engineering and Management from the University of Stuttgart, Germany. The research interest of Mr. Suaznabar has been mainly focused on the understanding of fluvial processes, river engineering, and physical modeling of bridge scour processes. Zhaoding Xie biography: Zhaoding Xie (Dr.Xie) is a research engineer in hydraulics focusing on the application of CFD at Genex Systems with base at the FHWA Turner-Fairbank Highway Research Center (TFHRC) J. Sterling Jones Hydraulics Laboratory in McLean, VA. Dr. Xie obtained his Ph.D. in the civil engineering department at University of Nebraska-Lincoln. The major research field of Dr.Xie includes the mechanism of sediment transportation, computational fluid dynamics and application in hydraulics, scouring around hydraulic structures. He participated in the projects including in the drag and lift on a submerged bridge deck, pressure flow scour (HEC18), In-site Scour testing device, riprap protection around an abutment, flume inlet design and other work assisting in the design and optimization using CFD method.
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