Experimental Investigation of Stepped Spillways’ Downstream Erosion Control using Microsilica- Structured and Nano Materials

Nano-structured materials are waterproof, they can be used for scouring reduction in alluvial beds. In this research impact of clay additive and nanomaterials and silicafume to sediment bed materials of stepped spillway on control of erosion and scouring in investigated as a nonstructural solution. First effects of steps count and flow regime on downstream scouring were studied. The results show that increasing the steps count on the same slop of chute and in a skimming flow regime on the steps the depth and length of the scouring on step spillway downstream increases. Then impact of some injected additives to the sediment bed with the same step count and skimming flow regime was investigated. The results proof the positive effect of clay and its mixture with nanoclay and silicafume on improvement of scouring length and depth reduction on the weir downstream. The best performance between three different compositions is related to the mixture of clay with nanoclay and silicafume in which they contributed in reduction profile of scoring by 48.74% and 46.38% respectively compared with the reference model. At the same time injection of clay to the sediment bed reduced the depth and length of scouring by 35.63% and 20.88% and injection of clay with nanoclay reduced the depth and length of scouring by 41.41% and 37.75% respectively. These results can state the success of clay, nanoclay and silicafume on scouring control mechanism at downstream of hydraulic structures especially in flood discharges.