SCOUR AROUND A COMPOUND PIER

Abstract

Realistic estimation of scour depth around spur dikes, bridge abutments and piers is needed for economical design of foundation structure. Literature available on this research shows that scour depth is generally found more in case of pier as compared to guide bank, spur, groyene. And a lot of studies carried out on Uniform circular piers in laboratories. Also effect of pier geometry and variation of foundation is seen on the scouring (i.e. maximum depth and temporal variation). Bridge piers having non-uniform cross section over their height are said to be compound piers. Mostly circular piers resting on large diameter well or caisson are adopted in Indian subcontinent for road and railway bridges. Literature available suggests that scouring is being affected by many factors viz. pier geometry, sediment characteristics, stratification of channel bed, and placing of footing with respect to bed level. In these studies, Mathematical model for computation of temporal variation of scour, Mechanism of scouring (3-D boundary layer separation, horseshoe vortex and other vortices), and Temporal Variation of scouring are presented for different hydraulic and mainly structural conditions, such as placing of footing (with top of footing below, at and above the natural bed level) in channel and variation in pier geometry.