http://civilustaad.blogspot.com/
The classification structure can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described underneath (with the exception of Pt):
If the soil has 5–12% by weight of fines passing a #200 sieve (5% < P#200 < 12%), both grain size distribution and plasticity have a major effect on the engineering properties of the soil, and dual notation may be used for the group symbol.
For example, GW-GM corresponds to "well-graded gravel with silt."
If the soil has more than 15% by weight retained on a #4 sieve (R#4 > 15%), there is a considerable amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change.
For example, SP-SM could submit to "poorly graded SAND with silt" or "poorly graded SAND with silt and gravel."
SOIL
CLASSIFICATION
The Unified Soil Classification System (USCS) is a
soil classification system used in engineering and geology to explain the
texture and grain size of a soil.
The classification structure can be applied to most unconsolidated materials, and is represented by a two-letter symbol. Each letter is described underneath (with the exception of Pt):
If the soil has 5–12% by weight of fines passing a #200 sieve (5% < P#200 < 12%), both grain size distribution and plasticity have a major effect on the engineering properties of the soil, and dual notation may be used for the group symbol.
For example, GW-GM corresponds to "well-graded gravel with silt."
If the soil has more than 15% by weight retained on a #4 sieve (R#4 > 15%), there is a considerable amount of gravel, and the suffix "with gravel" may be added to the group name, but the group symbol does not change.
For example, SP-SM could submit to "poorly graded SAND with silt" or "poorly graded SAND with silt and gravel."
