Experimental Study of Scour due to Abutment- Pier Interaction

Abutments and piers are commonly used in vicinity of each other in a bridge, whose interactive effect is generally not considered in their respective design. The article presents findings of an experimental study to evaluate the interaction between pier scour and abutment scour in noncohesive boundary surface under clear water conditions. Present laboratory study has been carried out with models of a single abutment (wing wall type), along with two circular piers of diameter 30mm and 60mm in a cohesionless material. Two piers models are also placed independently at four different locations 0d, 1d, 2d, 3d (d = diameter of pier) from the abutment and maximum scour depths occurring in the vicinity of abutment & pier were noted. It is concluded from the study that there is instantaneous growth (120%-160%) in magnitude of maximum scour depth for smaller size of pier of diameter 30mm and almost 15% growth in maximum scour depth for 60 mm diameter pier due to presence of the abutment in their vicinity. However, abutment scour got increased approx by 15% due to proximity of a pier of 30mm diameter & by 20%-40% due to proximity of 60mm pier diameter, indicating that effect of presence of smaller diameter pier on the maximum depth of abutment scour is not significant. It was also evident that either pier or abutment presence in a bridge leads to substantial increase in their maximum scour depth when placed closer to pier or abutment as compared to farther locations.