Environmental Engineering Reference
In-Depth Information
60
60
50
50
50
40
c
f
40
40
30
c
f
f
30
30
20
c
20
20
10
10
10
0
0
0
Loose
Medium compact
Compact
Very Compact
0
−
L
+
−
MC
+
−
C
+
20
30
40
50
60
70
80
90
100
Relative density
D
R
and compactness rating
FIGURE 3.59
Relationship between sampler blows per 6 in, sampler diameter, gradation, and compactness. (From Burmister,
D. M., ASTM Special Technical Publication No. 322, 1962, pp. 67-97. With permission. Reprinted with
permission of the American Society for Testing and Materials.)
where
C
N
is a correction factor,
σ
vo
the effective overburden pressure (
γ
t
γ
w
)
z
, (in tsf) and
P
a
1 tsf (95 kN/m
2
).
N
value at a depth corresponding to
σ
1
is considered to be a stan-
dard.
Seed (1979) presented recommended curves for the determination of
C
N
based on aver-
ages for results obtained in various studies (Marcuson and Bieganousky, 1977a, 1977b) as
given in
Figure 3.60.
For practical applications, the curves resulting from equations 3.46
and 3.47 approximate the curves of Figure 3.60. Investigators have proposed that the max-
imum value for
C
N
should not exceed 1.7.
C
N
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0
0.5
1
2
D
r
= 40 to 60%
D
r
= 60 to 80%
3
4
FIGURE 3.60
Recommended curves for determination of
C
N
based on averages from WES tests. (From
Seed, H. B.,
Proceedings ASCE, J. Geotech. Eng.
Div.,
105, 201-255, 1979. With permission.)
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