Interaction between Pier Scour and Other Components of Scour under Clear-Water Conditions

Abstract

Interaction between various components of bridge scour is a complex phenomenon. Bridge submergence during high flooding leads to the scour mechanisms becoming even more complex. Thus, to find the interaction between various components of bridge scour, a detailed investigation has been conducted by using scaled-down models in a hydraulic laboratory. Scour experiments were conducted with free, submerged-orifice, and overtopping flow (OT) under clear-water conditions. The results show that the total interactive scour caused by simultaneous effects of pier, abutment and contraction scour results in a reduced equilibrium scour depth compared to the sum of all individual components acting independently. A comparison with HEC-18 methodology shows that the large bias of over-estimation has been eliminated by the suggested model in this study. However, the interaction of pier scour with vertical contraction scour remains as a sum of individual scour components with the exception of the recommendation of using Lyn’s modified model to calculate vertical contraction scour. Field examples from past historical events have been used to validate the model, and they show good agreement with the suggested model.