Influential factors on free swell test

Free swell is one of indexes in representing the expansibility of clayey soil and makes great valuable reference in the judgment of expansive soil. Free swell test is commonly used in China to obtain the swell-shrinking property of clay due to its simple equipments and easy operation. But, the deficiencies of standard for soil test method and trade specification exit in the regulation and explanation of the details for free swell test, that leads to the great difference in the test results when totally operating according to methods in the standards and specifications for the same soil sample. In order to make free swell test more complete and test result more stable, two main artificial factors related to test result are discussed and analyzed and some suggestions for improving the current standards and specifications are given.