1
UPDATE OF THE SPT- AND CPT-BASED LIQUEFACTION TRIGGERING PROCEDURES
presented by
I. M. IdrissProfessor Emeritus, University of California at Davis
Consulting Geotechnical Engineer, Santa Fe, [email protected]
Presented at the
1st WORKSHOP ON GEOTECHNICAL EARTHQUAKE ENGINEERING
"Liquefaction Evaluation, Mapping, Simulation and Mitigation"
Organized by
Earthquake Engineering Research Institute (EERI) San Diego Chapter
San DiegoSeptember 12, 2014
Reference material
The presentation today is based on material published in the following report:
Boulanger, R. W. and Idriss, I. M. (2014) "CPT and SPT Based Liquefaction Triggering Procedures", ReportUCD/CGM- 14/01, Department of Civil and Environmental Engineering, University of California, Davis, CA, 138 pp.
This report can be downloaded from:
http://retrocee.engr.ucdavis.edu/faculty/boulanger/PDFs/2014/Boulanger_Idriss_CPT_and_SPT_Liq_triggering_CGM‐14‐01_2014.pdf
2
Outline of Presentation
1. Magnitude Scaling Factor (MSF)
Modified MSF expression to be a function of magnitude, soil type, and denseness of the soil
2. Update of SPT-based approach
Added 24 Case Histories (14 from Turkey & 10 from Taiwan)
Incorporated new MSF expression
No change in CRR versus (N1)60cs
3
Outline of Presentation
3. Update of CPT-based approach
Changed qc1N as a function of FC
Changed CRR versus qc1Ncs
4. Examination of the CPT-based case histories in terms of the soil behavior type (SBT) index, IC
MAGNITUDE SCALING FACTOR (MSF)
4
DEMAND -- CSR
The value of CSR for each case history is calculated usingthe following expression:
v
vo maxdM 7.5 ; ' 1 atm
vo
a 1 1CSR 0.65 r
' KMSF
Acc
eler
atio
n
Time
Acc
ele
rati
on
Time
Acc
eler
atio
n
Time
Effects of duration
M = 5.1
M = 6.5
M = 7.3
5
History of the development of MSF:
1. Seed et al. (1975): proposed a relationship between "Number of Equivalent Uniform Cycles, Neq" & Magnitude, M, which led to the initial development of "MSF Values".
2. Seed & Idriss (1982): Tabulated "MSF Values" as a function of M; used shaking table test results by DeAlba et al. (1976) relating CRR to "Number of Uniform Cycles".
3. Idriss (1999): Used results of cyclic tests on frozen samples by Yoshimi et al. (1984) to derive a revised relationship between Neq & M, which resulted in a revised MSF relationship.
4. Boulanger & Idriss (2014): Modified MSF expression to be a function of magnitude, soil type, and denseness of the soil, as summarized in this presentation.
MSF used to account of effects of duration
Cyclic Stress Ratios Used in Re-Deriving EquivalentUniform Cycles as a Function of Earthquake Magnitude
Number of Cycles, N
1 10 100
Cyc
lic
Str
ess
Rat
io
0.04
0.06
0.08
0.2
0.4
0.6
0.8
2
0.1
1 Test results by Yoshimi et al (1984)on frozen samples
Test results by Yoshimi et al (1984)on tube samples
Test results by DeAlba et al (1976) normalizedto a relative density = 68% at 10 Cycles
(see Fig. 3 re: Legend for individual test series)
bCRR aN
6
Number of Cycles Required t o Cause 5 % D.A. St rain
1 10 10 0
Cy
clic
St
res
s R
at
io ( d
/2 o
') a
t N
um
be
r o
f C
yc
les
= N
Cy
clic
St
res
s R
at
io ( d
/2 o
') a
t N
um
be
r o
f C
yc
les
= 1
5 c
ycl
es
0 .2
0 .3
0 .4
0 .6
0 .8
2
3
0 .1
1
Based on Test Result s byYoshimi et al (19 8 4 )
Based onTest Result s by DeAlba et al (19 76 )
Normalized t o a Relat ive Densit y = 6 8 %
Normalized Cyclic Stress Ratios Used in Re-DerivingEquivalent Uniform Cycles as a Function of Earthquake Magnitude
Earthquake Magnitude, M
4 5 6 7 8 9
Nu
mb
er o
f E
qu
ival
ent
Str
ess
Cyc
les
0
10
20
30
40Seed & Idriss (1982)Idriss (1999)
Figure 62 – Mean number of equivalent uniform cycles at 65% of the peak stress versus earthquake magnitude.
Effects of duration
7
Figure 62 – Mean number of equivalent uniform cycles at 65% of the peak stress versus earthquake magnitude.
Effects of duration
Earthquake Magnitude, M
4 5 6 7 8 9
Nu
mb
er o
f E
qu
ival
ent
Str
ess
Cyc
les
0
10
20
30
40Seed & Idriss (1982)Idriss (1999)
Effects of duration
The number of cycles representing a given magnitude from theprevious figure can be used in the lab-generated CSR versus Nplot to obtain the level of CSR corresponding to that magnitude.This value of CSR divided by the CSR for a reference magnitude(usually M = 7½) is defined as a "magnitude scaling factor orMSF".
MSF is then used as a proxy for duration and is expressed as afunction of earthquake magnitude.
8
Effects of duration
Number of Cycles, N
1 10 100
CR
R
0.0
0.1
0.2
0.3
0.4Test results by DeAlba et al (1976) normalized
to a relative density = 68% at 10 Cycles(see Fig. 19 re: Legend for individual test series)
Magnitude = 7.515 cycles
Effects of duration
Number of Cycles, N
1 10 100
CR
R
0.0
0.1
0.2
0.3
0.4Test results by DeAlba et al (1976) normalized
to a relative density = 68% at 10 Cycles(see Fig. 19 re: Legend for individual test series)
Magnitude = 6.56.8 cycles
9
Number of Cycles Required to Reach ru = 100% or 5% DA Strain
1 10 100
CR
R a
t N
Cyc
les
/ CR
R a
t N
= 1
5
0.0
0.5
1.0
1.5
2.0
2.5
Ma
gn
itu
de
= 5
½
Ma
gn
itu
de
= 6
½
Mag
nit
ud
e =
7½
Ma
gn
itu
de
= 8
½
1.69
1.30
1.00
0.77
MSF
Illustration of the variation of MSF with number of cycles and magnitude.
Magnitude scaling factor values proposed by various investigators
Earthquake moment magnitude, M
5 6 7 8 9
Mag
nit
ud
e sc
alin
g f
acto
r, M
SF
0
1
2
3
Seed & Idriss (1982)
Ambraseys (1985)
Arango (1996)
Idriss (1999)
Tokimatsu & Yoshimi (1983)
Cetin et al (2004)
MMSF 6.9exp 0.058
4
10
MSF relationship for clays and plastic silts (Boulanger and Idriss 2007)
0.1 1 10 100
Number of Cycles, N, to reach 5% D.A. strain
0.1
1
0.2
0.4
0.6
0.8
2
0.08
0.06
0.04
Cy
clic
Str
ess
Rat
io C
SR
=
d /
2'
o
Yoshimi et al (1984):Cyclic TX on frozen samples
of dense Niigata sand
Silver et al. (1976):Cyclic TX on moist tampedMonterey sand ( DR=60% )
Toki et al. (1986):Cyclic TX on air pluviatedToyoura sand ( DR=50% )
b = 0.22
b = 0.10
b = 0.34
Effects of denseness on slope b
11
5 6 7 8 9Earthquake magnitude, Mw
0
1
2
3
0.40
0.34
0.280.220.16
b =
Variation in the MSF relationship with parameter b
Variation in the MSF relationship with (N1)60cs & qc1Ncs
5 6 7 8 9Earthquake magnitude, Mw
0
0.5
1
1.5
2
2.5
(N1)60cs=30, qc1Ncs=175
(N1)60cs=20, qc1Ncs=133
(N1)60cs=10, qc1Ncs=84
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UPDATE OF THE CPT-BASED APPROACH
Total number of CPT-based
case histories: 253Y/N/M 180/71/2
US case histories:Y/N/M 65/35/1
Japan case histories:Y/N/M 24/13/1
New Zealand case histories:Y/N 53/16
Other case histories:Y/N 38/7
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DEMAND – CSR
The value of CSR for each case history is calculated usingthe following expression:
v
vo max dM 7.5 ; ' 1 atm
vo
a r 1CSR 0.65
' MSF K
Key expressions – CPT-based procedure
m
aN
v
0.264
c1N
PC 1.7
m 1.338 0.249 q
c1 N cq C q
c1N c1 aq q P
Pa = atmospheric pressure having same units as qc
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Key expressions – CPT-based procedure
n
c v a'
a v
q PQ
P
s
c v
fF .100
q
2 2
C 10 10I 3.47 Log Q 1.22 Log F
C FC
FC
FC 80 I C 137
C 0, -0.29, 0.29
c1N ,cs c1N c1Nq q q
15
qc1Ncs
0 50 100 150 200 250
CS
RM
=7.
5,'
v=
1at
m
0.0
0.1
0.2
0.3
0.4
0.5
0.6
CPT data based on 2014 interpretation Process
Liq. No Liq. MarginalUSA
Japan
New Zealand
Others
Triggering relationship(Boulanger & Idriss, 2014)
Triggering relationship(Idriss & Boulanger, 2008)
De
pth
of
crit
ical
zo
ne
(m
)D
ep
th o
f cr
itic
al z
on
e (
m)
16
17
Soil Behavior Type (SBT) Index, IC
State Parameter,
CPT-based soil behavior type classification chart by Robertson (1990)
18
Liquefaction failure case histories (from Robertson 2010)State parameter, = -0.05
= -0.05
Normalized friction ratio, F (%)
0.1 1 10
No
rmal
ize
d c
on
e ti
p r
es
ista
nc
e,
Q
1
10
100
10001.4 < Ic < 1.64 [9]
1.64 < Ic < 2 [80]
2.0 < Ic < 2.2 [49]
2.2 < Ic < 2.4 [29]
2.4 < Ic < 2.6 [13]
CPT LiquefactionCase Histories
19
Normalized friction ratio, F (%)
0.1 1 10
No
rmal
ized
co
ne
tip
res
ista
nce
, Q
1
10
100
1000
State parameter = -0.05
1.4 < Ic < 1.64 [9]
1.64 < Ic < 2 [80]
2.0 < Ic < 2.2 [49]
2.2 < Ic < 2.4 [29]
2.4 < Ic < 2.6 [13]
CPT LiquefactionCase Histories
Normalized friction ratio, F (%)
0.1 1 10
No
rmal
ized
co
ne
tip
res
ista
nce
, Q
1
10
100
1000
State parameter = -0.05
1.4 < Ic < 1.64 [21]
1.64 < Ic < 2 [28]
2.0 < Ic < 2.2 [12]
2.2 < Ic < 2.4 [5]
2.4 < Ic < 2.6 [5]
CPT No LiquefactionCase Histories
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The Cone Penetration Test (CPT) has proven to be a veryvaluable tool for characterizing subsurface conditions andassessing various soil properties, including estimating thepotential for liquefaction.
The main advantages of using the CPT are that it provides acontinuous record of the penetration resistance and is lessvulnerable to operator error than is the SPT test.
Its main disadvantages are the difficulty in penetrating throughlayers with larger particles (e.g., gravels) or very highpenetration resistances (e.g., strongly cemented soils) and theneed to perform companion borings or soundings to obtain soilsamples.
Concluding remarks
Development of the CRR versus (N1)60cs or qc1Ncs relations arebased on using the equation:
Therefore, "forward" calculations should also be based onusing this equation.
Calculation of shear stresses by convolving an inadequatenumber of input rock motions can lead to serious over orunder estimation. The minimum number of input rockmotions appears to be 7, but this issue is still underinvestigation.
vo max dM 7.5
vo
a r 1CRR 0.65
' MSF K
Concluding remarks
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Elements that affect site response in order of importance:
Input MotionSoil ProfileSoil PropertiesMethod of Analysis
Concluding remarks
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