Geotechnical Engineering

DHARM

100 GEOTECHNICAL ENGINEERING

Wide range in grain-size andsub-stantial amounts of allintermediate particle sizes

Table 4.1

Unified soil classification system

Major Division

GroupSymbol

Typical Name

Classification Criteria

Field Identification

Procedures (Excluding

particles larger than 8 cm)

C

= u

D

60

/D

10

Greater than 4

More than 50% retain on No. 200ASTM Sieve

C

= c

(

D^30

D

(^2) ) D
10
60
×
Between 1
and 3
50% or more of coarse fraction re-tained on No. 4 ASTM Sieve
GP
Poorly graded gravels andgravel-sand mixtures, littleor no fines
Not meeting both Criteria forGW
Predominantly one size or arange of sizes with some in-termediate size missing
GM
Silty gravels, gravel-sand-siltmixtures
Atterberg limits plot below
A-
line and plasticity index lessthan 4
Non-plastic fines (for identi-fication procedures see MLbelow)
Clean gravels Gravels with fines
GC
Clayey gravels, gravel-sand-clay mixtures
Atterberg limits plot above
A-
line and plasticity indexgreater than 7
Plastic fines (for identifica-tion procedures see CL be-low)
More than 50% of coarse fractionpasses No. 4 ASTM sieve
SW
Well-graded sands and grav-elly sands, little or no fines
C
= u
D
60
/D
10
Greater than 6
C
= c
(
D^30
D
(^2) ) D
10
60
×
Between 1
and 3
Wide range in grain-sizesand sub-stantial amounts ofall intermediate particlesizes.
SP
Poorly graded sands andgravelly sands, little or nofines
Not meeting both criteria forSW
Predominantly one size or arange of sizes with some in-termediate sizes missing.
Clean sands
Sands with fines
SM
Silty sands, sand-silt mix-tures
Atterberg limits plot below
A-
line or plasticity index lessthan 4
Non-plastic fines (for identi-fication procedures see MLbelow)
SC
Clayey sands, sand-clay mix-tures
Atterberg limits plot above
A-
line and plasticity indexgreater than 7
Plastic fines (for identifica-tion procedures CL below)
Coarse grained soils
GW*
Well-graded gravels andgravel-sand mixtures, littleor no fines.
(Contd...)