A CALCULATION OF POROSITY AND SEDIMENT HEIGHT OF RIVERBED MATERIAL WITH BROAD PARTICLE SIZE DISTRIBUTION IN BED RIVER

Abstract

Many of conventional numerical simulations have a problem to evaluate the river bed variation and sediment load due to their disability to calculate the change in the porosity for sediment mixture with a wide range of particle size in gravel bed rivers. We proposed a two-particle-diameter closest packing formula that can explain previous two-diameter spheres packing experiment. A numerical analysis method was developed based on the formula and it was validated to calculate the porosity of mixed size sphere particles. Then we applied the model to the experiment with river bed material. The measurement results of the porosity for two-diameter packing of sediment particles with various diameter ratios were reproduced by the present formula. We also clarified that the relationship between the particle size distribution and the porosity at the closest packing measured with riverbed material are explained by the present model. Furthermore, the present model can provide good agreement with that of deposited sediment measured in gravel bed rivers.