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Abstract

Scour of spill-through abutments occurs due to the combined influence of geotechnical and hydraulic processes. The present study is among the first to address the geotechnical process associated with the failure of the compacted earth, spill-through abutments, and the effects of the geotechnical strength of spill-slope soil on abutment scour. Laboratory experiments were completed to determine how soil shear strength affects abutment scour. The experiments, which primarily involved sand compacted to varying strengths, and some clayey soils, led to new and useful insights. A major new finding is that abutment failure begins at the water line of the spill-slope's upstream corner, where flow constriction around an abutment exposes and erodes spill-slope soil to the highest values of flow velocity and turbulence. Once initiated, erosion continues toward the middle portion of the spill-slope face, and then progresses downstream. Spill-slope erosion is marked by the formation of undercut, exposed vertical blocks of embankment soil whose failure occurred relatively quickly once the spill-slope face began eroding. Abutments formed of stronger soils took longer to erode, had bigger blocks of failed soil, and produced deeper scour of the channel around the abutment. Rapid failure of an abutment resulted in shallow scour depths.

How to Cite

Ng, Kam, Robert Ettema, Edward Kempema, Ram Chakradhar, and Joshua Fuller. Geotechnical Limit to Scour at Spill-through Bridge Abutments: Laboratory Investigation, MPC-15-280. North Dakota State University - Upper Great Plains Transportation Institute, Fargo: Mountain-Plains Consortium, 2015.