Investigation on vertical wall abutment scour under steady and unsteady flow in compound channels

摘要

The depth of local scouring in a vertical wall abutment in a compound channel was investigated. Steady and unsteady tests were carried out for different lengths of abutments. For steady tests, the time evolution of scour depth and scour hole geometry was determined for different flow conditions. The experiments revealed that the more is the flow intensity and abutment length, the more are the scour depth and their ultimate values. Finally, a dimensionless equation that correspond the evolution of scour depth to the flow intensity and the abutment length was proposed. For unsteady flow, a symmetric hydrograph was applied and scour depth evolutions was determined. By stepping hydrograph, successive scour depths were obtained by using steady flow estimation during each step. The results calculated from the stepped hydrograph were almost identical to the results measured from the flood hydrograph.