On the Local Scour Around Group Piers in Series by Experimental Tests

Abstract

In this article a physical model is presented. A trapezoidal shape of channel with 1.45 m width, 1 meter depth and banks slope of 1H: 1.5V was applied. Circular piers (6, 8 and 10cm diameter) were examined under three dissimilar flow discharges of 50, 65 and 80 lit/s and three different median bed material sizes equal to 0.94, 1.31 and 2.12 mm. Seven different longitude distance to pier diameter ratios (1, 1.5, 2, 2.5, 3, 4 and 5) were examined. Measurement of scour depth (upstream, around and downstream of pier) was accomplished in 10, 15, 20, 30, 60, 120, 240 and 360 minutes from the beginning of each examination. The results indicated that 30%-40%, up to 65% and more than 90% of local scour occurs at first two, 10, 120 and 200 minutes from the beginning of test respectively. The effect of dissimilar parameter especially the distance between piers on scour depth at group piers in series was evaluated and the results were compared to other researchers. It was found that our results is best fitted with the general form of well known Sheppard et al. (2004)'s equation.