DESIGN FOR TUNNEL-TYPE SEDIMENT EXCLUDER

A tunnel-type sediment excluder is commonly used at the headwork of a canal for preventing excess sediment from entering the off-taking cana l. In such excluders the sediment-laden water, which flows mainly near the bed, is made to flow through the tunnels provided at the canal be d. It may be then discharged back into the river downstream through th e undersluice bays. Comparatively sediment-free water in the top layer s is allowed to enter the canal. Presently, the only hydraulic princip le utilized in its design is that energy loss is kept to a minimum and a minimum velocity of flow is ensured through the tunnel for the nond eposition of the coarse material. In the present paper, established co ncepts of sediment transport are used to outline a procedure for the d esign of a tunnel-type sediment exluder when the river bed material is nonuniform in nature. The procedure suggested herein is illustrated w ith examples using the field data and the results obtained are compare d with the available observations from the prototypes.