Analysis of size distribution of soil particles considering floc formation and application to Kunigami maaji soil

Abstract

Effect of floc density on the size distribution of soil sample determined by sedimentation is analyzed by comparing the result of conventional method and that based on the newly proposed method. In the proposed method, the relation between the settling velocity and the diameter of a soil floc determined by the experiment is incorporated into the analysis of pipet method. Experiment was conducted using Kunigami maaji soil picked at the field of sugar cane in Okinawa island. Tow types of soil sample treated with 0.1M CaCl₂ solution and 0.1g/l (HPO₃) ₆ solution were prepared. The power law relation between the floc density and the floc diameter was confirmed from the measurement of the settling velocity against floc diameter. No significant difference in the relation between V_f and D_f was found even if the sample was treated in different manner. In the analysis of size distribution, the proposed method was found to give a successful result for the sample treated with CaCl₂ solution. However, result in dispersed sample didn't agree with result of microphotograph in a range below 10μm. This inconsistency was interpreted as unique colloidal characteristics of the soil sample.