What is another term that describes undesirable soils known for expansion?

Plastic soils are indeed characterized by their ability to undergo significant volume changes due to moisture fluctuations, which makes them prone to expansion and contraction. This property is critical when considering their behavior in various civil engineering and construction applications, such as foundations and earthworks.

Plasticity in soils means that they can retain water and become soft, leading to expansion. This property is particularly problematic because it can lead to damage to structures if proper precautions are not taken during construction or if inappropriate materials are used in foundations or backfill.

In contrast, silty soils tend to have different engineering properties, typically not exhibiting the same level of expansion as plastic soils. Loamy soils, which are a mixture of sand, silt, and clay, generally exhibit more favorable physical properties for construction and do not have the extreme expansion properties of plastic soils. Contracting soils, while they may suggest a similar understanding, does not capture the broader behavior of expansion associated with undesirable soils known for plasticity. Thus, the term plastic soils accurately reflects the nature of these problematic soil types.