Author(s): Hazumu Tadokoro; Shoji Fukuoka
Linked Author(s): Shoji Fukuoka
Keywords: Particle shape; Vertical sorting; Gravel-bed rivers; Volume concentration; Numerical slope failure experiment
Abstract: Gravel-bed rivers are composed of particles of various shapes and sizes. The shapes and sizes of particles in the gravelbed river have great influences on sediment transport and river bed variation. Numerical methods of sediment transport and river bed variation in gravel-bed rivers must consider effects of particles shapes properly. This paper mainly demonstrates the effects of particle shapes on vertical sorting by comparing motions of spheres and gravels in numerical slope failure experiments in the water. The numerical experimental results demonstrated that the angle of repose of gravel particles was larger than that of spheres due to engagement effects of gravel particles. Moreover, slope failures of both upper part and lower part of sphere-particles stratum progressed gradually. On the other hand, the slope failure of lower part of gravel particles progressed more slowly compared to sphere particles due to large engagement effects among particles. Then upper particles of gravel fell down in a relatively long time. In both cases of spheres and gravels, large particles tended to move parallel to the channel bed, but small particles tended to drop in the lower part of the channel. Consequently, the vertical sorting made particles on the slope surface larger. Particles on the surface of the sphere slope became larger than those of gravels. Moreover, the porosity of gravels in the moving layer was larger than that of spheres.
Year: 2015