What is the distinguishing feature of Type A soil?

Type A soil is characterized primarily by its unconfined compression strength. Specifically, Type A soil has an unconfined compressive strength of 1.5 tons per square foot (tsf) or greater. This classification is important in geotechnical engineering because it indicates that Type A soils have a relatively high strength, making them less susceptible to deformation under load.

In contexts such as excavation or slope stability, recognizing the properties of Type A soil can guide engineers in determining appropriate support and safety measures. Higher strength soil like Type A is typically employed in construction projects, which aids in minimizing risks associated with soil failure.

Other characteristics, such as the presence of fissures, low strength, or high plasticity, are indicative of other soil types and should not be considered distinguishing features of Type A soil. For example, fissured soils may indicate instability, while soils with less than 0.5 tsf strength would typically fall into a different classification of soil that is weaker and more prone to collapse under applied loads. High plasticity often characterizes clay soils but does not necessarily align with the strength criteria established for Type A soil.