Coarse-grained soils are those for which more than 50% of the soil material by weight has particle sizes greater than
0.075 mm. They are basically divided into either gravels (G) or sands (S).

According to gradation, they are further grouped as well-graded (W) or poorly graded (P). If fine soils are present, they are grouped as containing silt fines (M) or as containing clay fines (C).

For example, the combined symbol SW refers to well-graded sand with no fines.

Both the position and the shape of the grading curve for a soil can aid in establishing its identity and description. Some typical grading curves are shown.

Curve A - a poorly-graded medium SAND

Curve B - a well-graded GRAVEL-SAND (i.e. having equal amounts of gravel and sand)

Curve C - a gap-graded COBBLES-SAND

Curve D - a sandy SILT

Curve E - a silty CLAY (i.e. having little amount of sand)