Experimental investigation on ingestion of sediment into trench weirs: Fid-Bau Portal

Experimental investigation on ingestion of sediment into trench weirs

Kumar, S. / Ahmad, Z.

Trench weirs are commonly constructed across boulder rivers. Such weirs have definite advantages, as they do not obstruct the flow of the river, but susceptible to ingestion of bed load sediment having size smaller than clear opening of the rack into the trench. This study deals with the experimental study of the mechanics of movement of sediments, over and across the racks and also quantification of the sediments ingested/trapped into the trench, which shall be useful for fixing the dimensions of the trench weir for minimum ingestion of sediment. This study reveals that the trajectory of the sediments movement and stream lines of flow are different due to different inertia and for the minimization of entry of sediment into the trench, the clear opening length shall be kept less than the jumping length of the particles. For ratio of size of sediment to clear spacing of rack less than 0.75, the total incoming sediment is ingested into the trench. However, for ratio greater than 0.75, the ingested sediment depends on the diverted discharge. A relationship is developed to estimate the percentage of incoming sediment, ingested into the trench. The proposed relationship computes the ingested sediment into the trench within ±3% error.