Novel Riprap Structure for Improved Bridge Pier Scour Protection

Abstract

This study introduced a new riprap placement design for the purpose of reducing bridge pier scour. The design consisted of embedding a layer of the riprap around the pier, flush with the surrounding bed, with a depression to help guide the horseshoe vortex. The new countermeasure design was tested among other conventional riprap placement designs in clear-water flow conditions and transition-flow conditions. The transition-flow condition is the evolution period from clear water to live bed where the bed has yet to reach an equilibrium state. The new countermeasure design was found to reduce greatly the depth and volume of scour in both flow conditions, up to 81.0% and 92.3%, respectively, which was more than any other riprap countermeasure tested. In addition, the new design used 18% less riprap material while also experiencing less shape deterioration when compared with a traditional flat riprap cover. Therefore, installing riprap in this specified shape yields an improved scour countermeasure that could help preserve infrastructure and increase public safety.