What happens to expansive soils when there is an increase in moisture content?

Expansive soils, often composed of clay minerals like montmorillonite, exhibit a significant change in volume in response to moisture fluctuations. When there is an increase in moisture content, these soils can absorb water and swell, leading to an increase in volume. This swelling behavior is a characteristic trait of expansive soils, making them problematic for construction and engineering, as they can exert pressure on foundations and other structures.

This increase in volume occurs because the water molecules enter the spaces between the clay particles, causing them to separate and expand. The degree of swelling can vary depending on the type of clay present and the amount of moisture added. Understanding this behavior is crucial for site assessments and the design of foundations in areas where expansive soils are prevalent. Recognizing that increased moisture leads to swelling helps in planning appropriate mitigation strategies to counteract potential structural issues.