Influence of Sediment Gradation on Scour Downstream of Block Ramps

The scour process downstream of block ramps is an important research topic of value to engineering practice. The object of the present experimental study is to examine the scour mechanism in order to predict the main geometrical parameters of the scour hole downstream of block ramps. The investigations have been conducted using two physical models located in the hydraulic laboratory of the Department of Civil Engineering in Pisa, Italy. Sediments with different values of the nonuniformity parameter were used as channel bed material. Moreover, different ramp slopes, ranging from 1/4 to 1/12, were tested. Equations and graphs demonstrate that the results can be interpreted by means of simple relationships in the case in which a ridge is present downstream of the scour hole