Effect of pile arrangement on local scour depth at pile groups

The local scour at pile is the main reason for bridges failure. Although numerous researches have been done on scouring, the appropriate equation to predict scour at bridges foundation has not been presented yet. In this research, an experimental study on clear water scour at pile groups under steady flow at threshold velocity is presented. Uniform bed material with median particles size of 0.8 mm, in a 46 m long, 1.52 m wide and 1.9 m deep flume were used. The objectives of this study are to present changes in scour at multiple piles due to the pile arrangements and present empirical relationship to estimate the scour depth at multiple piles with different arrangements. Wide ranges of pile group arrangements are studied when the diameters of piles were 60 mm and 42 mm. The number of piles in line with flow (m) and normal to flow (n) were regularly increased at each successive experiment. In total, 40 experiments were carried out used possible arrangements of pile group where maximum number of n and m were 4 and 10 respectively. It was observed that the scour at pile group is affected by pile arrangements. The collected data were used to propose a new empirical equation to compute effects of the studied variables (m and n). The outputs of this research can be used to improve the pile group arrangement procedure to