Using nanomaterial to minimize the local scour downstream of sluice gate

Prediction of scour depths is an important aspect related to the overall stability of hydraulic structures. In this research, small-scale laboratory experiments were carried out to explore the effectiveness of mixing different percentages of Nanomaterial (Silica fume) to non-cohesive (alluvial) movable bed soil to develop mixture of bed material with significant characteristics to minimize the local scour caused by high-velocity jets downstream of a sluice gate. The experiments were executed employing 9 jet Froude numbers ranged from 1.88 to 2.81 associated with 3 heights for gate opening, and 3 tailwater depths. The bed material has 5 different percentages of Silica fume mixed by weight and 2 types of mixing with and without water were used. Ninety-nine experiments were conducted, out of which 9 experiments were done using fine sand as a bed material for the referenced cases. Graphical relationships were presented for maximum scouring and silting depths for different hydraulic conditions and bed materials. This research demonstrated that the type of mix (dry-mix or wet-mix) had a significant influence on the geometry of scouring and silting for the same flow conditions and the mixed percentage ratio of Silica fume. For dry-mix, the scouring and silting depths increased as the percentage ratio of Silica fume increased. While for wet-mix, the scouring and silting depths decreased as the percentage ratio of Silica fume increased. Also, the wet-mix effectively reduced the local scour volumes by 34.65% and 83.05% and decreased the silting volumes by 33.35% and 89.42% according to the percentage of Silica fume. Using a bed mixture of 8% Silica fume wet-mix showed 83.05% and 89.42% decrease in scouring and silting volumes, respectively, compared to pure fine sand bed material. From practical and financial aspects, the presented composition of bed material can effectively replace the smooth apron or at least decrease its length to reduce the construction cost. The obtained results present an untraditional technique for local scour protection downstream hydraulic structures. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.