Parametric Study on Abutment Scour under Unsteady Flow

Experimental results on scour at abutments under unsteady clear water flow condition are presented. Three shapes of short (abutment length/upstream depth < 1) were tested, namely, rectangular/vertical wall, semi-circular, and trapezoidal/45° wing-wall embedded in uniform sands two sizes having d50 = 0.52 mm 0.712 mm. The unsteadiness the is considered form flood hydrographs three forms, namely: advanced hydrograph (Type I), symmetrical II), delayed III) with maintained all cases. experimental findings used to represent influence various parameters bridge abutments. It was observed that rectangular greater than trapezoidal semi-circular depths finer sediments those coarser sediments. In addition, based study effect hydrographs, it noticed yields as compared other Further, method superposition correction shape factor, a semi-empirical model using dimensionless proposed compute temporal evolution conditions. this include shallowness, intensity, sediment coarseness, time factor. found corresponds well data time-dependent obtained from present experiments (unsteady flows) reported by different investigators (steady flows).