Effect of Abutment Length on Abutment Scour in Compound Channels

Bridge failures due to scour at bridge abutments clarify importance of scour prediction and scour reduction. Abutment length is one of the most important parameters influencing the scour process. Most of bridge abutments are located in floodplains and locating them in main channels are less common. One of common cases in floodplains is the existence of vegetation cover. Scope of this study is to investigate the effect of vertical wall abutment length on scour in compound channels. Experiments were carried out in different abutment lengths، vegetation concentrations under clear water condition. Results show that for constant flow depth، with increasing the abutment length، the effect of vegetation on reduction of scour depth increased. Also، with increasing the abutment length at the minimum flow depth، the scour depth got larger at a rapidly increasing rate. With increasing flow depth، this rapidly increasing rate changed to a slowly increasing rate.