Three-Phase and Gel Models of Soils in the Analysis of Experimental Results

Abstract

It is common to consider the experimental soil physics results from the standpoint of a three-phase soil model. Along with the three-phase model, a gel model of soils is used. These models are based on different principles: in the three-phase model, solid phase constancy and liquid mobility; in the gel model, the ability of soil gels to swell, harden, and reduce water mobility. The purpose of this work is to assess the applicability of three-phase and gel soil models to analyzing the study results of some physical properties of soils. The studies were carried out with the zonal soil series: sod–podzolic, gray forest, chernozem, and chestnut soils. The following methods were used in this work: vibration viscometry, laser diffractometry, and electrical resistivity of soils. Unexpected results were obtained in the study of the soil’s physical properties. Firstly, the curve of the relationship between the moisture content of soil samples and the viscosity of pastes prepared from them reached the maximum at the point of limited availability of water (PLAW). Secondly, under the increased mechanical action on soil pastes, the particle size increased rather than decreased in them. Thirdly, the soil electrical resistivity–moisture relationship maintains a uniform course in the PLAW area. Meanwhile, at this water content, the continuous liquid phase framework providing moisture and electrical conductivity disappears in the soils. Fourthly, moist soils dry out in a desiccator over water. It is not possible to explain these results from the standpoint of the three-phase soil model generally accepted in soil science. For this reason, the gel model of soils was used to analyze and explain all the results obtained.