Particle‐Size Distribution Characterization for the Coarse Fraction of a Granite Soil: II. Disintegrating Granite

Abstract

The object of this study was to test the incomplete gamma function previously developed as a descriptor for grapite disintegration. Samples of disintegrating granite were taken from several sites at three locations in a hot semiarid environment in south‐central Africa (southern Rhodesia). These samples were from surface rock, profile corestones, and disintegrating rock at the base of the soil profile. Particlesize distributions were obtained using the standard sieving and pipette method. For materials > 10 mm, Martin's diameter was measured directly.The incomplete gamma function was fitted to these data, and also to U.S. and French data from the literature, for granite in an apparently similar state of disintegration. The values for the degree‐of‐disintegration parameter were fairly uniform. The mode of disintegration appeared the same regardless of site. The two‐parameter incomplete gamma distribution was found to be a reasonably good descriptor of the particle‐size distribution of disintegrating granite. The mean size appeared to be a sensitive and useful single‐valued descriptor for these distributions.