STUDY ON VARIATIONS IN POROSITY AND VOLUME OF SEDIMENT MIXTURE WITH CLASSIFICATION

Abstract

 It is necessary to develop a calculation method of riverbed topographical change with the variation in grain size distribution for the evaluation of deposition and sediment flushing mechanism in reservoirs, and the effect of sand supply on the downstream river. However, the conventional method based on the active layer concept has problems to evaluate the change in the sediment porosity and the thickness of the layer. In this study, the experiment was conducted with a straight horizantal channel to clarify the change in sediment volume and the porosity with the sediment sorting. It was investigated that the porosity increased in the flow direction. While the volume change associated with the variation in the grain size distribution was large at the initial stage, it decreased rapidly, approaching asymptotically to about 1.1 times of the erosion volume in this experiment. The experimental porosity in a finite thickness was reproduced by the Eulerian deposition model. A calculation method of riverbed is proposed based on the model and validated through the comparisons with the experimental results.