Ranges of Change of Soils Physical Properties Indices

Abstract

Dispersive soils are multi-phase, multi-component systems. The number of phases and components depends on the amount and state of water in soil voids determining the values of index physical properties, which in turn affect the thermal, strength, deformation and other properties of the soil. Studies of soil physical properties involve the determination of four values – the mass and volume of a sample in a natural state, the mass of a dried sample, and the volume of solids which are used to determine the main parameters. This study examines variations in the main indices of soil physical properties based on the known provisions that an increase in soil moisture content to complete saturation does not lead to an increase in soil volume and that full moisture capacity for thawed soils is maximum moisture content, while frozen soils may have moisture contents far in excess of full moisture capacity due to moisture migration. Formula are presented to calculate the mass of soil with a change in moisture content and the volume of frozen soil in the range of moisture contents exceeding the full capacity, from which formula have been derived for determining the density, porosity and degree of saturation. Also, a relation is shown to exist between gas and moisture contents based on the formula obtained earlier relating the physical index properties of soils. Graphs have been derived relating the index physical properties of a clay silt specimen to moisture content, which are thought to be qualitatively common for all soil types. In the moisture content range from 0 to full capacity, soil density increases linearly from the value equal to dry density to the maximum value and the degree of saturation increases linearly from 0 to 1, while the relative gas content decreases linearly from the value equal to porosity to 0. When the moisture content of frozen soil exceeds the full capacity, bulk density and dry density decrease as an attenuating curve, porosity and void ratio increase, the degree of saturation remains at 1, and the relative gas content is 0.