Erosion near hydraulic structures - Prediction and similarity laws in hydraulic models with fine sediments

Abstract

The knowledge of erosion processes and the maximum scour depth near hydraulic structures is crucial for applying design criteria for weirs, bridges, piers etc. Until now, there is no standard approach to be found in the literature for the estimation of the maximum scour depth. In contrast, the calculation of a scour hole includes a large range of variations for the calculated maximum depth and the scouring time, especially for fine sediments. Thus, model tests were carried out to predict the maximum scour depth with an applied physical model. Unfortunately, the scaling of sediment characteristics, in particular the scaling of fine sediments, includes different problems. Frequently, lightweight materials were used as model sediment. Experiments were carried out in the laboratory of the Leichtweiss-Institute for Hydraulic Engineering to investigate the scouring process behind a vertical gate. Therefore, sand and synthetic pellets were used as movable bed material. The data indicate the existence of similarity laws for the interaction sediment-flow field-erosion process in the transition zone.