Scour reduction in sand beds against vertical jets by applying sheet-like countermeasures

Abstract

The scour observed at the landside ground behind coastal protection facilities, such as seawalls and coastal dikes, due to tsunami overflows is the main reason for failures in such constructions. In this study, we focused on sheet-like (two-dimensional) scour countermeasures, which do not require large-scale excavation of the ground, and experimentally verified the effects of geonet and mesh sheets. By applying a vertical jet directly on the ground and increasing the external force, a situation close to the real scale conditions was reproduced. The experimental results show that the geonet material is able to significantly reduce the scour depth on both non-liquefied and liquefied grounds. We show that in the most effective case, the maximum pore-water pressure and the scour depth are reduced by about 91% and 86%, respectively, by the mesh sheet on the sand-bed surface.