Define: 1) Degree of saturation and 2) Air content.
i) Degree of saturation: The degree saturation is a ratio of the volume of water in the voids to the volume of voids. It is expressed as per cent
ii) Air When soil mass is completely dry the voids present in the soil mass are completely filled only with air. The liquid phase remains absent in such case
Va = Vv Air content is defined as ratio of volume of air to volume of voids, i.e ac =Va/Vv