New experimental configuration for investigation of debris accumulation effect on local scour at bridge pier and abutment

Debris accumulation around bridge piers and abutments threatens stability by intensifying scour and risking collapse. While the effects of debris on individual bridge components have been studied, the combined influence of debris in the presence of both pier and abutment remains underexplored. This study experimentally examines how debris shape, thickness, and pier-abutment distance affect local scour depth under clear-water conditions. Experiments were conducted in 8 m long, 0.8 m wide, and 0.6 m deep flume, filled with 15 cm of uniform sand ([Formula: see text] mm, [Formula: see text]) and operated at a constant discharge of 30 l/s. Results showed that increasing the relative thickness of rectangular debris from 0.09 to 0.39 lead to a 41% increase in scour depth at the pier and 47% at the abutment. Reducing the pier-abutment distance from 0.2 to 0.1 caused an increase in scour depth by 21% and 16%, respectively. Thicker debris enhanced vortex intensity, resulting in deeper scouring. Among the tested shapes, rectangular debris caused the most significant scour, while triangular debris had the least effect. In all cases, maximum scour occurred at the abutment. These findings emphasize the practical significance of considering debris-structure interactions to improve bridge safety and resilience in engineering design.