Effects of shape, inlet blockage and wing walls on local scour at the outlet of non-submerged culverts: undermining of the embankment

Abstract

Drainage works using culverts are potentially affected by local scour risk. Local scour process is a complex phenomenon affected by many factors. Most of them have been analyzed in previous studies, either individually or in small groups. However, no fully joint analysis has been developed so far. Since the number of factors and interactions is high, the main objective of this work was to determine which of them best represents the dimensions of the scour hole and the embankment undermining. 80 experiments have been designed and developed and studied by ANOVA techniques. These results highlight the effect of wing walls with a floor slab at the outlet and the inlet blockage, showing them to be of major importance. The influence of the tailwater depth and the culvert shape on the scour hole are confirmed as relevant factors, as well as the presence of wing walls. Some interactions have been identified as relevant. The main outcome of this work is the set of factors and interactions that has significant impact on local scour process occurring beside a culvert. This selection is the basis for performing further experimental work in the future to obtain a general empirical law that quantifies this kind of local scour.