Porosity

The geometry of the pore system of soil is just as complex as that of the solid phase. Descriptions of the pore system, however, tend to be in relatively simple terms such as total porosity, volume percentage of pore-size distribution, and the latter two characterizations being based on a capillary-tube model with which the experimental observations identified. Characterizations of the pore system are important in investigations of the storage and movement of water and gases, in studies of the development of root systems by plants, in problems concerned with the flow and retention of heat, and in investigations of soil strength. Soil pore systems are not simply a bundle of straight, uniformbore capillary tubes. Nevertheless, if capillary theory can be assumed valid in the pore system, the radius calculated with the equation will at least represent the minimum size of pore neck through which an air-water interface must move during drainage.