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DESCRIPTION
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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