According to USCS classification, Fat clay is characterized by a liquid limit equal to or greater than what percentage?

In the Unified Soil Classification System (USCS), fat clay is specifically defined by its plasticity characteristics. It is categorized as a clay that has a high enough liquid limit—specifically, a liquid limit equal to or greater than 50%.

Clays are classified based on their plasticity index and liquid limit, which indicate how these soils behave when moisture content changes. A liquid limit of 50% or more shows that the clay can retain significant moisture and undergo considerable plastic deformation. This characteristic is crucial in the determination of engineering properties and ground behavior, especially in applications requiring stable foundation support.

The definition of fat clay being 50% or higher in liquid limit aligns with both the engineering principles involved and standard classifications used in soil mechanics. Therefore, recognizing that fat clay must meet or exceed this threshold of 50% allows engineers to accurately assess and work with these soil types in construction and environmental applications.