Identification of Safe Distance between Eccentric Bridge Piers to Minimize Scour by Considering Mutual Interference and Morphology

Increasing traffic demand necessitates constructing new bridges adjacent to existing ones, resulting in eccentrically arranged piers. Preventing excessive scour to avoid bridge failures is crucial by managing potential interference among piers. Limited research has addressed these specific bridge arrangements, highlighting the need for further investigation. In this study, experiments were conducted varying eccentricity (e) and flow intensities to evaluate their influence on the temporal scour depth (ds) and identify conditions that minimize scour. Single-pier experiments were also performed to assess scour severity with rear pier positioning. Dimensional analysis revealed that flow shallowness, flow intensity, Froude number, time, and e are the key parameters influencing ds. The postexperiment analysis focused on scour geometry and bed morphology. The lowest ds for the front pier occurred when e equals 2.12h, whereas the rear pier experienced 25% more ds. Conversely, the minimum ds for the rear pier occurred when e equals 1.2h, with the front pier showing a 14% lower ds. Overall, the minimum ds for the safest bridge pier design was identified at e equals 2.1h for the selected hydraulic conditions. Furthermore, multilinear regression analysis using integrative data from literature and this study provided a superior equation for estimating ds compared with multi-nonlinear and all literature equations. This research aids in selecting geometric parameters, particularly eccentric spacing, to reduce scour, ensuring safe and cost-effective bridge pier construction.