Environmental Engineering Reference
In-Depth Information
C
R
−
2.7
C
R
−
1.7
C
R
−
0.9
3
1
−
1/2
3/4
3/4
4
8
16
30
50
100
200
Sieves
0
10
20
35
50
35
100
90
80
70
60
50
40
30
20
10
0
200
Tr a c e
Little
Series of type S curves
Regularly varying
Fineless and range
of grain sizes
Some
And
And
Some
20
10
Little
Tr a c e
60
20
6
2
0.6
0.2
0.06
0.02
0.006
0.002
0
D
10
Grain size (mm)
Uniform scale of fractions
Gravel
M
Sand
M
C
Slit
Nonplastic
Boulders
cobbles
F
C
F
C
Clay-soil plasticity and clay-qualities
0.02
mm
228
9 in.
76.2
25.4
9.52
3/8 in.
2.0
0.59
0.25
0.076
2.00
Nos.
10
60
3 in.
1 in.
30
Sieves
(a)
C
R
C
R
100
100
−
Ty p e L
Ty p e E
Balance
plus and minus
area for upper
and lower branch of curve
50
50
+
10
0
10
+
0
100
D
10
D
10
100
+
Ty p e D
Ty p e D
−
50
50
+
10
−
10
+
0
+
0
Log of grain size
D
10
Log of grain size
D
10
(b)
FIGURE 3.9
Distinguishing characteristics of grain size curves: fineness, range of grain sizes, and shape: (a) type S grain
size curves and (b) type of grain size curve. (From Burmister, D. M., ASTM, Vol. 48, Philadelphia, PA, 1948.
Copyright ASTM International. Reprinted with permission.)
Coefficient of uniformity C
u
— the ratio between the grain diameter at 60% finer to
the grain diameter corresponding to the 10% finer line, or
●
C
u
D
60
/
D
10
(3.3)
Significance
Gradation relationships are used as the basis for soil classification systems. Gradation
curves from cohesionless granular soils may be used to estimate
γ
N
or
D
R
is known, estimates can be made of the void ratio, porosity, internal friction angle, and
coefficient of permeability.
γ
D
and
γ
L
, and, if
Gradation Curve Characteristics (Burmister, 1948, 1949, 1951a)
The gradation curves and characteristic shapes, when considering range in sizes, can be
used for estimating engineering properties. The range of sizes
C
R
represents fractions of a
uniform division of the grain size wherein each of the divisions 0.02 to 0.06, 0.06 to 0.02,
etc., in Figure 3.9 represents a
C
R
1. Curve shapes are defined as L, C, E, D, or S as given
in Figure 3.9 and are characteristic of various types of soil formations as follows:
S shapes are the most common, characteristic of well-sorted (poorly graded)
sands deposited by flowing water, wind, or wave action.
●