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Research Journal of Environmental Sciences

Year: 2011  |  Volume: 5  |  Issue: 5  |  Page No.: 399 - 413

A Relationships to Determine the Critical Hydraulic Gradient and Noncohesive Sediment Transport Discharge in Rockfill Dams

S.A. Mousavi, E. Amiri-Tokaldany and M.H. Davoudi


In this research by conducting laboratory experiments along with dimensional analysis, we investigated the nondimensional sediment discharge capacity and critical hydraulic gradient in rockfill dams. Rockfill dams are a type of grade control structures used to protect river bed against fluvial erosion and also to stabilize the river banks by decreasing the bank height. One of the main issues on utilizing rockfill dams is to keep its permeability enough so that it could be able to pass the flow as well as the sediment load through its body during flooding, avoiding sediments resettlement inside the pores. In this regard, the design of rockfill dams should be carried out so that the available hydraulic gradient is always kept greater than the critical hydraulic gradient, which consequently results in transporting the sediment through the dam body. In this research, a relationship to estimate the critical hydraulic gradient to transport noncohesive sediment through rockfill dam body is introduced. We tested the new equation using a set of published data and we found MRE equal to 0.4%. Also, using laboratory data obtained from tests on a rectangular rockfill dam, performing dimensional analysis and using linear regression, an exponential relationship for the required discharge to transport the sediments through the body of rockfill dam is presented. When we tested the validity of exponential relationship, we found a good accuracy for the equation (MRE = 9.4%) indicating that the introduced relation predicts the nondimensional sediment transport capacity well.

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