Expansive soils and clays

Abstract

Expansive soils are known to cause damage to driveways, floors, and foundations and in monetary terms this damage annually amounts to billions of dollars. Structural, linear, and residual shrinkage are the three distinct stages in soil shrinkage of which linear shrinkage is predominant over a wide moisture range and is directly related to moisture loss. Interparticle and intraparticle porosity is largely considered responsible for the shrink-swell phenomenon in these soils. Soil characteristics like clay mineralogy and dry density and environmental factors such as moisture content, moisture fluctuation range induced by climate, ground water, and vegetation, and the state of stress are known to influence the shrink-swell potential of the soil. These soils are characterized mainly by liquid limit and plastic limit, clay content, or COLE (Coefficient of Linear Extensibility), a term used in soil classification by USDA. The swell-shrink is limited to what is termed as an active zone in the upper few meters affected by seasonal moisture fluctuations and is related to the depth of surface cracks in these soils. To overcome the hazardous effects due to expansion, a soil test is recommended prior to construction of a structure. Treatment of soil with lime, gypsum, sand, and other non-swelling materials is known to mitigate swelling.