Mohammad Vaghefi

This study investigated scour and sedimentation processes around a cylindrical bridge pier in two consecutive channel bends. These tests were conducted for different positions of the piers on the path and for different critical velocity ratios (U/ Uc). Therefore, the scour variations were investigated for piers installed at eight different positions of the two consecutive channel bends for three different cases of U/Uc (0.9, 0.95, and 0.98). The results indicated that as the piers were fixed at the subsequent positions of the upstream bend, the scour depth arose in the vicinity of the piers; installation of the pier at the 0° angle resulted in the minimum scour depth and its position at 90 and 135° angles bred the greatest scour depth. In addition, from the beginning to the middle of the downstream bend, this trend continued to rise, so a 45% increase in the highest scour depth at the fore of the bridge pier was observed when the pier position was altered from 180 to 270° angle. However, there was a falling trend in the next half of this bend to the end (from the 315° angle onward). With the increased U/Uc, the highest amount of increase was observed in variations in the maximum scour area parameter, so that a raised U/Uc from 0.9 to 0.95 and then to 0.98 at the 270° angle increased the maximum scour area by respectively 90 and 95%.