A correlation for the shrink swell index

Site classification to AS2870-2011 requires the soil shrinkage index, Ips. A common assessment method is to carry out a shrink swell laboratory test to calculate the shrink swell index (Iss), which is then used to develop the soil shrinkage index. To undertake a shrink swell index test, an intact thin wall tube sample of cohesive material is required. In hotter and drier areas of Australia, including northern Victoria, it can be difficult to recover intact cohesive samples. The geotechnical practitioner is often required to consider other methods to estimate Iss in order to provide the required site classification. This paper considers a variety of laboratory tests results including Atterberg Limit, Particle Size Distribution, Hydrometer and Iss results from clay samples within Victoria (including Melbourne) to provide an improved correlation to estimate Iss when thin wall tube sampling is not practicable. The data presented to support the correlation includes published test results by others and unpublished test results from projects the author has been involved in.