STUDY ON THE FORMATION OF OPENWORK GRAVEL LAYERS AND ITS FILLING-UP MECHANISM WITH MATRICES

Gravel layers of gravel-bed river are commonly filled with matrices of sand and silt. In some fluvial conditions, there are “openwork gravel layers”, that is, gravel layers without matrices. In this study, the formation of openwork gravel layers was observed in a field, and a filling-up process was also observed. The filling-up rates were measured under several hydraulic conditions in a flume, where the process was demonstrated and the rate was measured by putting iron powder into upstream end of the observed point at fixed intervals during the filling up process of openwork gravel layer. Summarizing these results, the rate of its filling-up process was predicted by a simple formula.