Influence of collar's shape on scour hole geometry at circular pier

Abstract

Bridge collapses, which are frequently caused by scouring or other hydraulic complexities, have disastrous socioeconomically consequences. Accordingly, this paper offers clear water scour experimental investigation that assesses the impacts of circular and novel hexagonal collar shapes on scouring around circular piers which embedded in a uniform sand bed. Scour geometry was analyzed for both protected and unprotected piers, along with evaluating the percentage reductions of the scour hole dimensions and volume. The results demonstrate that the suggested collars have a considerable effect on separation, stagnation, and dissipation of the impinging downflow and vortices, resulting in a substantial impact on the scour geometry and significantly mitigates local scour. In conjunction with the laboratory data, empirical predicting formulas for scour dimensions and novel coefficients for the effect of collar shape are proposed. To incorporate a novel consideration of estimating scour depth at collared piers, the common prediction equations were updated by adding the newly developed collar shape coefficient. The proposed and upgraded formulas are compared and validated, and the findings demonstrate robust consistency.