Abstract: Free swell ratio is a key index for identifying expansive soil, which applies to cohesive soils with particle size less than 0.5 mm.  Since the testing does not involve complex equipment or testing procedures, it has been used widely in China to measure the expansive characteristic.  Many researchers has raised concerns about the uncertainties in the testing method, which may affect soil classification.  This paper provides a stateofart discussion on potential errors that may be induced throughout the entire testing procedure, based on a comprehensive literature review and a series of laboratory tests.

Key words: Free swell ratio test, Expansive soil, test, Influence