A bridge pier scour model with non-uniform sediments Available to Purchase

Pier scour is a significant problem affecting the safety of bridges. For given hydraulic and geometric conditions, accurate prediction of scour with non-uniform sediments is important, but this need has not been fulfilled. The purpose of this research was to develop a three-dimensional model for scour prediction and to verify the model using laboratory measurements. The model allows for selective transport of non-uniform sediments, particle hiding and bed-level change in response to scour and deposition. The development of scouring around a circular pier on a mobile channel bed with non-uniform sediments was successfully predicted and scour depth prediction agreed well with the measurements. It was found that scour patterns emerge from the lateral sides of the pier and migrate towards its upstream nose. Upstream of the pier, strong downflow and vortex motions develop and effectively remove sediments from the foot of the pier; at equilibrium, the bed-surface slope almost reaches the angle of repose of sediments. On the upstream side, the scour hole has the shape of almost half a cone. Grain size non-uniformity reduces the magnitude of scour. These findings are of relevance to the safe and cost-effective design of pier foundations. The modelling techniques are computationally efficient and are useful for field-scale application.