An analogy can be made between the mechanisms of water transport in partially frozen soils and those in unsaturated soils. By use of this analogy a Darcian approach is applied to the analysis of coupled heat-fluid transport in porous media with freezing and thawing. With the aid of a numerical model, freezing-affected soil-water redistribution and infiltration to frozen soil are examined from a phenomenological point of view, and the effects of soil type and initial conditions on the response of a hypothetical soil column are studied. In general, the model shows that the rate of upward redistribution of soil water to a freezing zone at the soil surface decreases from coarse-textured soils to fine-textured soils and decreases with increase in depth to the water table. Subsequent redistribution during melting of the frost wedge is shown to occur at a rate less than that associated with freezing. Infiltration to partially frozen soil is also shown to have a significant influence on soil-water redistribution and the response of the groundwater table.

Analysis of coupled heat-fluid transport in partially frozen soil

The history of soil physics in its earliest manifestations is the history of soil science inasmuch as the earliest scientific observations and measurememts appear generally to be of soil physical properties. In fact, physical properties of soil have been noted in numerous cultural contexts, and it would be difficult to identify at just what point in historical time observations of such properties were sufficiently analytical, or measured with sufficient care, to be referred to as scientific. Hence, the best that can be said is that soil physics began in antiquity. Where and in what early culture it began would be equally difficult to determine and most histories inevitably will bear the mark of the cultural background of the writer. Moreover, the history of soil physics involves innumerable people, of diverse interests and backgrounds, increasing almost unmanageably by the beginning of the 20th century. By mid-century, the beginning of the contemporary period of the author’s professional career, even the subfields of soil physics have become too extensive to cover adequately in a short history. Hence, selection of persons and topics to include becomes increasingly difficult and little attempt is made here at complete and comprehensive coverage, leaving the task to future historians with perspective improved with time. What is covered here must of necessity bear the mark of the writer and his own interests.

Early Soil Physics into the Mid-20th Century

Publisher Summary This chapter discusses the soil–water behavior, as described by transport coefficients and functions Substantial advances in knowledge and understanding of soil–water behavior have come about through the development and application of flow concepts and theory based upon proportional-type water-transfer coefficients and functions These coefficients or functions arise from flow equations that express proportionality, between the velocity of water transfer and a pressure-gravity type of driving gradient The earliest water-transport coefficient proposed for porous materials appears in the law of Darcy One-dimensional water flow in layered systems is easily amenable to theoretical analysis, by a suitable application of Darcy's law The analysis predicts that the hydraulic conductivity of the least permeable layer is not the sole determining factor for water flow through a layered system Darcy-type analysis of layered systems has also been successful, in predicting the development and magnitude of soil-water suction, in water-saturated sublayers of soil, overlain by a material of reduced conductivity The Darcy proportionality equation also permits mathematical generalization into certain types of partial differential equations that can be solved for the boundary conditions of various water-flow problems

Soil-Water Behavior as Described by Transport Coefficients and Functions

Changes in the soil temperature and solute concentration occur continually under
natural field conditions. Examples of the variations in solute concentration are
given in chapter 14, particularly Fig. 14-13 and 14-14. In addition to this type of
change induced by moisture flow, the concentration of the soil's solution oscillates
between saturation under dry conditions to very dilute values after a rain or
irrigation. Soil temperature, like solution concentration, continually changes. Its
variation is conveniently classified as diurnal (Fig. 13II-1) and seasonal (Fig.
13II-2). The diurnal thermal changes are generally significant to a depth of 20
or 30 cm; the soil zone which contains the greatest proportion of plant roots. The
seasonal temperature wave extends well below the zone of most crop roots.

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The Dynamics of Soil Water. Part II. Temperature and Solute Effects

An experimental investigation of the behavior of soil water movement under unsaturated transient conditions is reported for the case of vertical infiltration into a sandy loam and silt loam soil material. Water was allowed to enter at a small constant suction into air-dry columns of soil and its subsequent distribution followed with a gamma radiation attenuation device. An analytic expression of water content as a function of depth and time was obtained by multiple regression analysis from which it was possible to determine the instantaneous flux and the water concentration gradient at given water contents. During the early stages of infiltration the relationship between the flux and gradient was linear as prescribed by the Darcy equation. At later times when the gradient became less steep linear proportionality broke down. Non-linearity at low water gradient was evidenced for both soils throughout a wide range of water contents. The magnitude and direction of the departure from linearity was similar for both soils indicating the deviations were possibly not due to specific soil properties, but rather to an inherent characteristic of the flow system itself.

Flow of water under transient conditions in unsaturated soils

The temperature dependence of soil water vapor presure was studied with a psychrometric vapor pressure technique in the range of 0.96 to 1.00 relative vapor pressures and below 0.96 with gravimetric and calorimetric heat of immersion techniques. For Millville silt loam at constant water content, the relative vapor pressure decreased with increasing temperature. Both differential and integral entropy values were calculated. The difference between the partial molar entropy of pure free water vapor and the partial molar entropy of adsorbed water led to the conclusion that soil water molecules are arranged, on the average, less randomly than water vapor molecules. At the same time, comparison with the entropy of vaporization of pure water suggested a more random arrangement of molecules in soil water than in free liquid water.

S. A. Taylor

Papers

The Temperature Dependence of Soil Water Vapor Pressure

A Constant Temperature Bath Controlled with a Precision of 0.001° Centigrade1