Soil Classification

5.1 Recognize that soils with similar properties may be classified into groups and subgroups according to their engineering behaviors, and discuss the importance of the two classification systems (AASHTO and Unified soil).

5.2 Discuss the AASHTO classification system and how it relates to soil mechanics.

5.3 Discuss the Unified soil classification system and how it relates to soil mechanics.

5.4 Compare the Unified soil classification system with the AASHTO classification system.

Different soils with similar properties may be classified into groups and subgroups according to their engineering behavior. Classification systems provide a common language to concisely express the general characteristics of soils, which are infinitely varied, without detailed descriptions. Currently, two elaborate classification systems are used commonly by soil engineers. Both systems take into consideration the particle-size distribution and Atterberg limits. They are the American Association of State Highway and Transportation Officials (AASHTO) classification system and the Unified soil classification system. The AASHTO classification system is used mostly by state and county highway departments. Geotechnical engineers generally prefer the Unified system.

https://uta.pressbooks.pub/soilmechanics/

Vincent Bongioanni, PhD, P.E.