Identification and classification of expansive soils

The swelling tendencies of expansive soils are quantified by the swell potential and swelling pressure parameters. The swell pressure of a soil is the external pressure that needs to be placed over a swelling soil to prevent volume increase, while the swell potential of an expansive soil is the magnitude of heave of a soil for a given final moisture content and loading condition. These expansive soil parameters can be directly estimated in the laboratory from special oedometer tests or indirectly from the index properties of the soils and the differential free swell test. However, swell potentials based on index properties are in far excess of the oedometer swell potentials. The soil properties, external pressure, and wetting-drying process affect the swell potential and swell pressure of expansive soils.