Shrink Swell

Shrink Swell Index

The shrink–swell index of clay refers to the extent certain clay minerals will expand when wet and retract when dry. Soil with a high shrink–swell capacity is problematic and is known as shrink–swell soil, or expansive soil.

The amount of certain clay minerals that are present directly affects the shrink-swell capacity of soil. This ability to drastically change volume can cause damage to existing structures, such as cracks in foundations, walls, pavements etc.