Understanding the Shrink/Swell (Iss) Test for Quantifying Ground Movements in Reactive/Expansive Clays Due to Soil Moisture Variations

During the 1960's and 70's as the awareness of the potential for clay-based soils to change volume with variations in soil moisture, practitioners had difficulty with quantifying these ground movements. Also in Australia new housing construction changed from the more movement tolerant flexible clad dwellings with timber floors, to slab on ground (raft slabs) and brick and/or blockwork (cinderblock) walls, which are very sensitive to all types of ground movement. Initially practitioners used the Atterberg limit suite of tests or one or more of them. Over time, there was one school of thought that contended that in preparing a sample for the Atterberg limit tests, the natural structure of the soil would be destroyed; therefore the outcome would not correlate well with the performance of the natural insitu clay. The proponents of this theory developed the shrink/swell test.