How does swelling differ if a foundation is built on dry soils?

Swelling in the context of soils, particularly in relation to foundations, typically refers to the behavior of expansive clay soils when they undergo moisture changes. When a foundation is built on dry soils, particularly expansive clays, the initial condition is one where the soil is dry and likely to remain stable.

If the foundation is constructed on dry soils, the primary concern would be moisture absorption. In the absence of additional moisture, these dry soils exhibit low swelling behavior because there isn't enough water to cause the clay particles to expand significantly. However, once water is introduced (through rain, irrigation, or leaks), these soils can swell considerably, resulting in potential upward pressure on the foundation.

High shrinkage often accompanies this phenomenon due to the distinctive ability of these soils to contract significantly as they dry out. Therefore, when considering the behavior of dry soils under conditions of moisture introduction, one expects a scenario where the swelling potential is significantly present but accompanied by the characteristic shrinkage behavior of expansive clays. Thus, low swelling can occur with significant shrinkage, making the understanding of the properties of expansive soils critical for construction practices.