Effect of submergence ratio of parallel wall on bridge abutment scour

Abstract

Scour at bridge abutment could be the main cause of bridge failures, leading to increased repair costs and reduced accessibility to roads. Thus, study and research on the prediction of scour at bridge abutment and its prevention is of great importance. The aim of this study was to investigate the effect of submergence ratio of parallel wall on vertical wall abutment scour. Experiments were conducted for different lengths and heights of parallel walls under clear water condition. In all experiments, the flow depth and the abutment length were 16 cm and 8 cm, respectively. Lengths of parallel walls were 4, 6, 8, 10, 12, and 16 cm (0.5, 0.75, 1, 1.25, 1.5, and 2 times of the abutment length, respectively), and parallel wall heights were 4, 8, 12 and 16 cm above sediment level (submergence ratio 25, 50, 75, and 100%, respectively, based on the ratio of the flow depth). By changing the flow pattern around bridge abutment, parallel walls are able to move maximum scour depth away from the upstream nose of the abutment and transfer it to parallel wall nose with less depth. Results of the study indicated that use of parallel wall has the best performance in the submergence ratio of 25%. Keywords: Scour, Bridge failure, Parallel wall, Submergence ratio, Clear water