Fractality of Grain Composition of Debris Flows
泥石流颗粒组成的分形特征

Debris flow is in essence the process of mass transportation controlled by its constitution that can be characterized by a wide-ranged distribution of grain size. Soil samples of debris flows of various densities have been collected from different regions and gullies. Analysis of grain composition, particularly for debris flow of high density, ρs > 2 g/cm3, reveals that the cumulative curve can be fitted by exponential function with exponent varying with regions and gullies. More importantly, the exponent falls into a narrow-valued domain and hence provides an index signing the activity of debris flows. Furthermore, fractality turns out to exist in grain composition and porosity; and fractal dimension has been derived from cumulative curves in a certain range of size, a range that defines the upper limit of grains constituting the matrix of debris flow. In analogy to concentration in fluidization of granular materials, fractal structure of porosity has proved to take a crucial part in initiation of debris flows.