Effect of Geonet on Scour Downstream of Horizontal Jets

Abstract

In river engineering, scouring around hydraulic structures constructed on erodible beds is highly attractive because of its impact on the stability of these structures. Accordingly, various researchers have always been looking for approaches to control or reduce the harmful consequences of this phenomenon in terms of both economic and environmental points of view. In this study, the application of geonets is introduced as a new approach to reduce local scour downstream of a sluice gate with a rigid apron. For this purpose, a geonet was installed in a specified depth under an erodible bed downstream of a sluice gate to prevent the development of scour hole. The experiments were performed on two different Froude numbers, three grain size distributions of noncohesive sediments, three types of geonets, and three different geonet installation depths. First, a number of tests were performed without a geonet (control experiment); then the other tests were conducted to investigate the effect of geonets on scour hole dimensions. The results showed that if the geonet installation depth is lower than the maximum equilibrium scour depth in the control experiment, the maximum equilibrium scour depth and the scour hole volume decreased and the scour hole length increased. In the following, to estimate the maximum equilibrium scour depth in the presence of a geonet, a relationship was developed for practical applications. In addition, using sensitivity analysis on the developed relationships, the effect of various parameters on the changes in maximum equilibrium scour depth in the presence of a geonet was evaluated.