Local scour around non-circular piers in clay-sand mixed cohesive sediment beds

Few investigations on local scour around circular piers embedded in clay-sand mixed cohesive sediment beds are available in the literature. However, no study has been reported on the local scour around non-circular piers such as round-nosed, square and rectangular piers embedded in clay-sand mixed cohesive beds. In the present investigation, laboratory flume based experimental data on local scour around round-nosed, square and rectangular pier models embedded in clay-sand mixed beds are reported. The effect of clay-content, water content and bed shear strength of the clay-sand mixed sediment bed on the scouring process, the scour hole geometry, the time variation of scour are described. In general, for circular piers embedded in non-cohesive sediment beds, equations are available in the literature for estimation of maximum equilibrium scour depth as a function of bed sediment and flow characteristics. The maximum equilibrium scour depth for the non-circular piers are obtained by multiplying the maximum equilibrium scour depth for circular piers with the correction factor for each pier shape. The data suggested that for clay and clay-sand mixtures, the shape correction factors are not constant values similar to that for the non-cohesive sediments, rather, these shape factors varied between certain ranges. (C) 2012 Elsevier B.V. All rights reserved.