Experimental Study of Longitudinal Extension Effects on Scour Patterns Around Single and Grouped Piers

Scour, defined as the erosion of a streambed around obstructions, poses significant risks to bridge piers, leading to structural failures and causing economic and human losses. This study investigates the effects of pier shape (modified by adding triangular and rounded noses to rectangular piers) and longitudinal extension on scour depth around single piers and pier groups. Experiments were conducted on rectangular single piers with a fixed width of ۰.۰۳ meters and varying lengths (length-to-width ratios, L/D = ۱–۹), as well as on groups of three-square piers with a side length of ۰.۰۳ meters and varying center-to-center distances (S/D = ۲–۵). The results demonstrate that adding a nose significantly reduces scour depth. The triangular nose on a rectangular pier (L/D = ۹) achieved the highest reduction, decreasing the maximum scour depth by ۸۰% compared to the benchmark model. In pier group configurations, increasing the distance between piers generally led to greater scour depths, as each pier began to act independently. The maximum scour depth observed in the S/D = ۳ model increased by ۲۵% relative to the benchmark. As pier spacing increased, scour holes became more distinct. Additionally, equipping the first pier in a group with a nose effectively diverted flow away from the piers, reducing scour more effectively than in nose-less configurations, with the triangular nose proving most effective. Overall, pier groups exhibited significantly higher scour depths than single piers.

کلیدواژه ها:

Local scour ، Square pier ، Maximum scour depth ، Single pier ، pier group