Local Bed Scour Due to Bridge Pier in a Bend

In this paper local bed scour due to bridge pier in a bend was studied by laboratory flume experiments. After three types of pier shape were located in a straight course (No. 6) and in a bend (No. in each place) which were place of center, inner bank side and outer bank side of flume, local bed scour shapes and characteristics were compared and analysed with each measured points. According to the results of experiments, each measured points in a bend the maximum scour depth increased from the inner bank side to the outer bank side. At the inlet of a bend (No. 8), the maximum scour depth increased about 10% with no relation to pier shapes. The amounts of maximum scour depth with pier shapes were increased circular semi-circle rectangular, rectangular pier in the order named. In a straight course, the scour length of front side piers and width of inner and outer side piers were almost the same values. In a bend, the scour length of front side piers and width of outer side piers were the same values but the scour width of inner side piers were longer about times (circular pier twice, semi-circle rectangular pier 3 times. rectangular pier 6 times) than the length of front side or width of outer side piers. Around the bridge piers in a bend, sprial flow which were caused by one of the bend flow characteristics added to the existed horseshoe vortex because the locations of maximum scour depth usually happened to front-inner side piers and the scour width increased in the inner side piers.