High plasticity inorganic clay soil is commonly referred to as what?

• A. Fat clay
• B. Lean clay
• C. Organic clay
• D. None of the above

Answer: (A)

High plasticity inorganic clay is commonly referred to as "fat clay." This type of soil has a high plasticity index, which indicates a significant ability to deform or change shape without cracking or breaking when subjected to moisture changes. Fat clay typically contains a higher proportion of clay minerals like montmorillonite, which contribute to its plasticity and cohesion.

Fat clay is often characterized by its ability to retain water and expand when wet, which can significantly affect engineering projects, such as foundations and roadways, due to its expansive behavior. Understanding the properties of fat clay is crucial for various civil engineering applications, including slope stability analyses and the design of structures built on or using this type of soil.

Other types of clay, such as lean clay, have lower plasticity and are less sensitive to moisture changes, while organic clay contains organic materials that affect its engineering properties differently. Hence, recognizing fat clay's characteristics helps engineers plan and mitigate issues related to high plasticity soils effectively.