Investigation the Energy Dissipation on Gabion Stepped Weirs and Downstream Hydraulic Jump Characteristics.

In recent years due to the simplicity construction, easy availability, durability and being economic, gabion structures have been widely used for excess energy dissipation in special for erodible channels. Gabion stepped weirs are mostly constructed to protect river beds and erodible waterways. These weirs due to proper capability in energy dissipation by the mixture of through and over flow, have been noticed by the designers. The effect of number of steps in gabion stepped weirs on the flow conditions and as a result on energy dissipation and verifying the characteristics of hydraulic jump in toe of these weirs are the main aims of this study. In order to investigate this effectiveness, 6 physical models with 3 different number of steps; 4, 6 and 8 with fixed slope of 1:2 (Vertical : Horizontal)were individually built for each series of experiments. The results show that the stepped weirs with gabion baskets have more energy dissipation in comparison to those without gabion baskets. Also, by reducing the number of steps, if nape flow is formed, relative energy dissipation would be increased. Results of above mentioned facts will prove that generally, weir of 4 stepped has the maximum, energy loss in the range of the experiments of this research study.