Environmental Engineering Reference
In-Depth Information
0.6
0.25
D 50 (mm)
2.0
M7.5
5
FC (%)
0.5
CPT Clean Sand
Base Curve
0.4
Liquefaction
No Liquefaction
0.3
0.2
0.1
Field Performance
Liq.
No Liq.
NCEER (1996)
Workshop
Stark & Olson (1995)
Suzuki et al. (1995b)
0
0
50
100
150
200
250
300
Corrected CPT Tip Resistance, q c1N
Figure 12.22.
CPT clean-sand base Cyclic Resistance Ratio curve for magnitude 7.5 earthquakes with
data from compiled case histories (Youd et al., 2001, reproduced from Robertson and
Wride, 1998, reproduced with permission of ASCE).
12.4.3.5 Evaluation of the Cyclic Resistance Ratio for M7.5 earthquake (CRR7.5)
from Cone Penetration Tests
The CRR from M7.5 earthquakes can be estimated from the curve in Figure 12.22. In this
figure q cIN is the normalized dimensionless cone penetration resistance calculated from:
q
C (q /P )
(12.17a)
c1N
Q
c
a
where
C(P/
)
n
(12.17b)
Qa
vo
where C Q
normalizing factor for cone penetration resistance;
vo
effective vertical
stress at the time of doing the CPT test (kPa); P a
atmospheric pressure (100 kPa);
n
exponent that varies with soil type; and q c
field cone penetration resistance meas-
ured at the tip in kPa.
The exponent n varies between 0.5 and 1.0 and can be estimated using the soil behav-
iour type index I c as follows (Youd et al., 2001; from Robertson and Wride (1998):
(a) Assume n
1.0 (characteristic of clays) and calculate the dimensionless tip resistance
Q from:
Q
[(q
)/P ][P /
]
n
[(q
)/
]
(12.18)
c
vo
a
a
vo
c
vo
vo
and the Normalized Friction Ratio F, from
F
[fs/(q
)]100%
(12.19)
c
vo
 
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