What characterizes expansive soils?

Expansive soils are characterized by their ability to undergo significant volume changes in response to variations in moisture content. These soils typically contain clay minerals, such as montmorillonite, which can absorb water and swell when wet, leading to an increase in volume. Conversely, when these soils dry out, they can shrink and decrease in volume. This behavior can create severe engineering challenges, as the ground movement associated with swelling and shrinkage can adversely affect the stability of structures built on or in these soils.

The properties of expansive soils necessitate special consideration in construction and civil engineering. Proper design and construction techniques, such as deep foundations or moisture control systems, are often required to mitigate the risks associated with their volumetric changes. Understanding the moisture sensitivity of these soils is crucial for any civil engineer working in regions where expansive soils are prevalent.

In contrast, the other choices do not accurately describe expansive soils. Soils that maintain a constant volume regardless of moisture are not expansive by nature. Stating that expansive soils are always stable and do not expand contradicts the fundamental characteristics of these soils. Lastly, while expansive soils can be found in arid climates, they are not exclusive to these regions, as they can also occur in humid areas depending on the geological and