Effects of ice cover on the incipient motion of bed material and shear stress around side-by-side bridge piers

Abstract

In the current study, a series of experiments were carried out to investigate the scouring process around side-by-side bridge piers under both open flow and ice-covered flow conditions. Three non-uniform natural sediments and four pairs of side-by-side bridge piers were used in this experimental study. The mechanism of incipient motion of the sediments under ice-covered conditions has been investigated. The role of the boundary shear Reynolds number, critical dimensionless shear stress, particle densimetric Froude number, grain size and roughness of ice cover on the incipient motion of bed material have been studied. Results show that the critical dimensionless shear stress increases with an increase in the particle densimetric Froude number. In addition, with an increase in the boundary shear Reynolds number, the critical dimensionless shear stress increases correspondingly. For the same critical dimensionless shear stress, the finer sediment needs a lower boundary shear Reynolds number for the incipient motion of sediment particles. For the same grain size of bed material, a lower critical dimensionless shear stress is needed for the incipient motion of sediment particles under rough ice-covered flow condition. Results of this study present valuable outcome to identify the feature of sediment motion near the scour hole under ice-covered flow conditions.