移動床のアーマリング機構に関する研究

Abstract

Armored bed surface, which is composed of particles coaser than those of theparent material, can be produced even if in the conditions that all the particles ofbed material are transported. The material of subsurface is usually finer. Thisemphasizes that an another mechanism except selective entrainment exists in thearmoring process of bed sediment.A multi-layer model, in which both the selective entrainment on bed surfaceand the vertical exchange of grains between surface and subsurface layers are takeninto account, is proposed. The model enable the bed material of surface to becoaser and that of subsurface to be finer. A flume test is performed with nosediment supply. Particle size distributions are measured during the run fortransported sediment and bed layers. The results predicted with the model arecompared well with data from the flume test for areal and temporal changes ofthose paticle size distributions. In comparison with the present study, the resultscalculated with a familiar two-layer model are shown.