Environmental Engineering Reference
In-Depth Information
5.3
Soils
5.3.1
Components
Basic
Defined by grain size, soil components are generally considered to include boulders, cob-
bles, gravel, sand, silt, and clay. Several of the more common and current classification sys-
tems are given in Table 5.27.
Major Groupings
On the basis of grain size, physical characteristics, and composition, soils may be placed
in a number of major groups:
1.
Boulders and cobbles, which are individual units.
TABLE 5.27
Soil Classification Systems Based on Grain Size
System
Grain Diameter (mm)
0.002
0.006
0.02
0.2
0.0006
0.6
2.0
19
76
4.76
0.06
M.I.T and
British Standards
Institute
f
mc
f
m
c
Clay
Silt
Sand
Gravel
0.001
2.0
0.25
9
24
76
0.005 0.074
American
Association of
State Highway Officials
(AASHO)
f
c
f
m
c
Colloids
Clay
Sand
Gravel
Boulders
Silt
2.0
76
0.002
0.05 0.25
0.5
U.S. Dept. of
Agriculture
(USDA)
vf
f
m
c
vc
f
m
Clay
Silt
Sand
Gravel
Cobbles
f
m
c
f
c
Clay and Silt
Sand
Gravel
Cobbles
Unified Soil
Classification System
(USDR,USAEC)
3
4
40
10
4
3 in
No. 200
in
Grain diameter in U.S. standard sieve sizes
3
3
8
No. 200
in
10
60
30
3 in
16
1.0 in
American Society
for Engineering
Education (ASEE)
(Burmister)
Silt
f
c
f
m
c
f
m
c
Clay and Silt
Sand
Gravel
Field
Identification
Hand
lens
Not
discernible
Visible to eye
Measurable
