Soil Classification Systems

Soil Classification Systems

Soils Classification Systems

Soil classification systems are used to class soils into groups and subgroups based on their engineering behavior
 Systems use common language to concisely express general characteristics without detailed descriptions

Types

 USDA
 AASHTO
 USCS

USDA Classification

 Complete a grain size analysis of soil
 Determine %G, S, M, C
 Adjust %S, M, C based on gravel content
 Use textural triangle to classify soil
 Use name modifier to account for gravel content

AASHTO Classification

 Developed in 1929 by the Bureau of Public Roads
 Currently uses seven major groups of soils, A1 to A7
 Provides a general rating of the soil as a subgrade for road construction
 Considers grain size distribution and plasticity of fines