Abstract:

To explore the grain-size fractal characteristics and transport law of widely-graded sediment, we conducted erosion test in a flume to analyze the fractal characteristics of bed material and bed load. Besides, we performed quantitative calculation and comparison of the granularity fractal dimensions of sediment in different bed materials and different flow velocities. Results showed that: the grain-size distribution in both bed material and bed load were of obvious statistical self-similarity, which meant that fractal characteristics existed. We also found that the variation of granularity fractal dimension was closely related to the sediment gradation. The value of granularity fractal dimension would decrease in the presence of stable roughened bed material. Furthermore, with the increase of flow velocity, the granularity fractal dimension would increase as for continuous grading bed material, while decrease as for discontinuous grading bed material. The value of granularity fractal dimension of bed load had an obvious negative correlation with its corresponding median diameter.

Key words: sediment, fractal, granularity fractal dimension, grain-size distribution, transport law, model test