UNIFIED SOIL CLASSIFICATION AND SYMBOL CHART LABORATORY CLASSIFICATION CRITERIA

PLASTICITY CHART

COARSE-GRAINED SOILS

FINE-GRAINED SOILS

(more than 50% of material is larger than No. 200 sieve size.)

(50% or more of material is smaller than No. 200 sieve size.)

Well-graded gravels, gravel-sandmixtures, little or no fines

greater than 4;

greater than 4;

between 1 and 3

between 1 and 3

=

=

=

=

Clean Gravels (Less than 5% fines)

C

C

C

C

D

D

D

D

D

D

D

D

D

D

u

u

c

c

60

60

30

30

x

x

10

10

10

10

60

60

Clean Sands (Less than 5% fines)

Above "A" line with P.I. between4 and 7 are borderline casesrequiring use of dual symbols

Limits plotting in shaded zonewith P.I. between 4 and 7 areborderline cases requiring useof dual symbols.

Determine percentages of sand and gravel from grain-size curve. Dependingon percentage of fines (fraction smaller than No. 200 sieve size),coarse-grained soils are classified as follows:

Less than 5 percentMore than 12 percent5 to 12 percent

GW, GP, SW, SPGM, GC, SM, SC

Borderline cases requiring dual symbols

Gravels with fines (More than 12% fines)

Sands with fines (More than 12% fines)

Well-graded sands, gravelly sands,little or no fines

Silty gravels, gravel-sand-silt mixturesAtterberg limits below "A"line or P.I. less than 4

Atterberg limits below "A"line or P.I. less than 4

Atterberg limits above "A"line with P.I. greater than 7

Atterberg limits above "A"line with P.I. greater than 7

Silty sands, sand-silt mixtures

Inorganic silts and very fine sands, rockflour, silty of clayey fine sands or clayeysilts with slight plasticity

Inorganic clays of low to mediumplasticity, gravelly clays, sandy clays,silty clays, lean clays

Inorganic silts, micaceous ordiatomaceous fine sandy or silty soils,elastic silts

Peat and other highly organic soils

Poorly-graded gravels, gravel-sandmixtures, little or no fines Not meeting all gradation requirements for GW

Not meeting all gradation requirements for GWPoorly graded sands, gravelly sands,little or no fines

Clayey gravels, gravel-sand-claymixtures

Clayey sands, sand-clay mixtures

Inorganic clays of high plasticity, fatclays

Organic silts and organic silty clays oflow plasticity

Organic clays of medium to highplasticity, organic silts

60

50

40

30

20

10

00 10 20 30 40 50

LIQUID LIMIT (LL) (%)

CL

CL+ML

CH

PL

AS

TIC

ITY

IND

EX

(P

I) (

%)

60 70 80 90 100

GW GW

GRAVELS

SANDS

SILTSAND

CLAYS

SILTSAND

CLAYS

HIGHLYORGANIC

SOILS

More than 50%of coarse

fraction largerthan No. 4sieve size

50% or moreof coarse

fraction smallerthan No. 4sieve size

Liquid limitless than

50%

Liquid limit50%

or greater

SW SW

GM GM

SM SM

ML

MH

PT

GP GP

SPSP

GC GC

SC SC

CL

CH

OL

OH

MH&OH

A LINE:PI = 0.73(LL-20)

ML&OL

UNIFIED SOILCLASSIFICATION SYSTEM