Investigation of Darcy Weisbach coefficient in porous media of rock fill dam in laden sediment flow

Due to the nature of permeability and economic consideration, Rock fill dam structures have been attracted by many engineers for flood relief pourpose. Knowledge of flow passing hydraulic is necessary for proper design of this structure. Due to the fact that most of former studies were based on no sediment laden flow, therefore the mechanism of sediment laden flow in this structure is studied experimentally. The experiments were conducted in a recirculating flume with various bed slope (i.e 0.001, 0.005 and 0.01), feeding sediment size (0.4, 0.6 and 0.8 mm) and 4 porous media (2 fine media and 2 coarse media). By simulating the flow in rock fill dam with pressurised flow in pipes, the basic relation between f and Re is obtained in sediment laden flow condition. The results showed that the friction coefficient of sediment laden flow is higher than non sediment flow and the previous empirical relationship doesn’t give accurate estimates of Darcy-Weisbach factor in sediment laden flow.