Abstract
Sands have a single grained structure, therefore the amount of its total porosity or its water holding capacity is usually characterized by such fractional systems as the shape and size of constituting particles, or the packed condition of the particle. In order to get a more adovanced insight to these properties, the author made a study using the commercial quartz sands as well as naturally occurring sands from Tottori and Fukuoka prefectures.
1. In each case of four kinds of sands having a single fraction system, the total porosity attained to ca. 52% in a loosely packed condition and to ca. 45% in a compactly packed one. The three different kinds of coarse sands, i.e., Very coarse sand (particle size was ca. 2-1mm in diameter), Coarse sand (1-0.5mm), and Medium sand (0.5-0.2mm), were usually provided with larger pores, which resulted in pF values less than 1.7. On the other hand, Fine sand (0.2-0.02mm) consisted of smaller pores, which induced pFvalues larger than 1.7 in ca. 70% of its total porosity.
2. The physical property of two fraction system of coarse sands showed only a slight change according to their different mixing proportion. However, on the mixing proportions of coarse and Fine sands in the fractional system the physical property changed remarkably. When the larger particles were mixed with the smaller ones at the ratio of 60: 40, the total pore space took the minimum value, but the mode of the frequency distribution of various pore sizes always showed the middle value of those of the respective single particle system.
3. The total porosity in the three fraction system sands showed a similar tendency with the two fraction system sands. When Very coarse and Fine particle sands were mixed together, the porosity changed remarkably, ranging from 42% to 53% in a loosely packed condition and from 32% to 46% in a compactly packed condition according to their mixing proportions.
4. The particles composing the natural sands were more or less uniform in their size and most of them belonged to the category of coarse sands. The total porosity averaged 45-50% of the total volume, being 1-5% less than that of the commercial quartz sands employed. The water holding capacity of certain natural sands took a slightly larger value than that of the commercial quartz sands. The values of certain natural sands were about the same as those suspected from the mechanical constitution of the commercial quartz sands. Thus, the total porosity as well as the water holding capacity of the natural sands could be duly estimated from the data on their mechanical constitutions.
