UNIFIED SOIL CLASSIFICATION SYSTEM

The unified soil classification system is commonly used to describe and classify unconsolidated sediments. The chart below contains information on how to classify a sediment.


MAJOR DIVISIONS GROUP SYMBOLS SOIL DESCRIPTION





COARSE GRAINED SOIL





(More than 50% material larger than the #200 sieve)

GRAVEL(more than 50% material larger than #4 sieve)

Clean
GRAVEL
(less than 5% fines)

 GW Well Graded Gravel; Sandy Gravel. Must have an equal distribution of fine and coarse gravel
GP Poorly graded Gravel; Sandy Gravel, Gap graded, little to no fines
GRAVEL
with fines(more than 12% fines)		 GM Silty Gravel; Silty, Sandy Gravel
GC Clayey Gravel; Clayey, Sandy Gravel

SAND
(more than 50% material smaller than #4 sieve)

Clean
SAND(less than 5% fines)

SW

 Well graded Sand; Gravelly Sand. Must have an equal distribution of fine, medium and coarse-grained sand
SP Poorly graded Sand; Gravelly Sand. Gap graded, little to no fines
SAND
with fines(more than 12% fines)		 SM Silty Sand; Silty, Gravelly Sand
SC Clayey Sand; Clayey, Gravelly Sand





FINE GRAINED SOIL

SILT AND CLAY
(Liquid limit less than 50)

 ML Inorganic Silt; Sandy or Clayey Silt.
Low to no plasticity
CL Inorganic Clay; Sandy or Silty Clay low to medium plasticity
OL Organic Silt or Organic Silty Clay
low to medium plasticity


SILT AND CLAY
(Liquid limit more than 50)(More than 50% material smaller than #200 sieve)

 MH Inorganic Silt, Micaceous or diatomaceous Sandy Silt, Elastic Silt, medium to high plasticity
CH Inorganic Clay
high plasticity
OH Organic Clay and Silt
high plasticity

HIGHLY ORGANIC SOIL

PT

 Peat and other highly organic soils