Study on Mixing Effects on Sediment Discharge of Sand and Gravel with Uniform Grain Size

Abstract

Mixing effects on sediment discharge of sand and gravel are discussed based on experiments with mixtures of sand and gravels with uniform grain size. Gravel discharge in mixtures becomes larger than that in uniform gravels when the volumetric percentage of gravels in mixtures is less than about 50%. This is caused by the reduction of repose angle of gravels on sand as well as their excess exposure to the flow. Sand discharge becomes generally smaller in mixtures, but when the gravel discharge increases largely with the mixing effect, sand discharge increases due to the effect of collision of gravel with sand.