Date of Award


Publication Type


Degree Name



Civil and Environmental Engineering


ADV measurements, Approach flow, Pier aspect ratio, Pier shape, Sacrificial piles, Scour


P. Williams


R. Balachandar




The complexity of the scour process around bridge piers leads to uneconomical pier design and unnecessary costs. This is due to the current scour estimation methods, which over-predict scour depth. Several aspects of scour have not been fully considered in pier design and require further investigation, such as the pier shape and aspect ratio. Further, scour countermeasures are used to protect the pier and reduce the scour depth. The first objective of the present investigation is to study the combined effects of pier nose shape and aspect ratio on scour geometry. The second objective is to better understand the effect of two different sacrificial piles arrays located in front of the piers in reducing scour. Experiments were carried out with different pier shapes and aspect ratios. The shapes used were round-nosed, sharp-nosed, round-edged, and square for piers with three aspect ratios (L/a = 1, 2, and 4). In addition, two triangular sacrificial pile arrays were used to study the role of sacrificial piles on scour reduction. The sharp-nosed pier with L/a = 4 recorded the minimum scour depth. Moreover, three sacrificial piles in a triangular arrangement resulted in maximum scour reduction. A new scour estimation method was developed using the present investigation and previous experimental results. The separation velocity, the pier shape, and aspect ratio were incorporated into the equation. These parameters were examined and found to be significant factors affecting scour.