A study on the effects of debris accumulation at sacrificial piles on bridge pier scour: I. Experimental results

Bridge failures are caused by various reasons, but the main reason is caused by scour at bridge pier. Debris accumulation on bridge piers is an ongoing problem nowadays. The study of debris accumulation on bridge piers has done by many researchers, but not any researches have done on debris accumulation on sacrificial piles, yet. The aim of this study is to estimate the effect of debris accumulation at sacrificial pile to bridge pier scour. Experiments were performed to understand the changes and interaction of scour over a range of flow depths and velocities in various cases like single pier cases, sacrificial piles cases, debris accumulated at single pier cases, and debris accumulated at sacrificial piles cases with different diameters and thickness of debris. Maximum scour depth in presence of debris accumulation at isolated pier and sacrificial piles have been compared to the maximum scour depth without the presence of debris accumulation. New relationships have been proposed to predict the effect of debris accumulation at sacrificial piles on bridge pier scour in term of relative maximum scour depth. The results of single pier with debris showed that the scour depth increased from 10% to 60% compared to single pier without debris. In sacrificial piles with debris the results showed that scour depth increased from 8% to 100% compared to sacrificial piles without debris. Through this experimental study the debris found to be effected to bridge pier scour. It was seen that the debris effected to the effectiveness of sacrificial piles. The effect of debris accumulation at sacrificial piles to bridge pier scour should be considered. Future researches are needed to consider more about the spacing between the pile, the angle of the pier to approach flow, and the angle of flow to the pier.