ESTIMATING METHOD FOR THE CONCENTRATION OF COARSER PARTICLES AT A DEBRIS FLOW’S FRONT CONSIDERING A FALLING OF SMALLER PARTICLES IN THE FLOW’S INTERIOR

Abstract

 We conducted flume experiments to investigate the mechanism of the concentration of coarser particles at the debris flow’s front with various particle-size distribution. In our experimental results, as the particle sizes of the material became coarser, the flow distance became longer or the flume gradient became lower, the concentration of coarser particles at the flow’s front progressed more remarkably. According to these results, a falling of finer particles through the interstice between the materials in the flow’s interior may explain the sediment sorting and the concentration of coarser particles at the flow’s front. We developed a numerical model to describe the concentration of coarser particles at the flow’s front by the above manner based on the conventional one-dimensional model. Our model could explain temporal changes in the percentages of all particle-size in the flow’s interior on various particle-size distributions of the materials, several flow distances and various slope gradients.