presentation asce seattle imidriss

1

CONTRIBUTIONS OF FIELD CASE HISTORIES TO GEOTECHNICAL EARTHQUAKE ENGINEERING

presented by

I. M. Idriss, Professor EmeritusUniversity of California at Davis

e-mail: [email protected]

Presented at the dinner meeting of the

ASCE SEATTLE SECTION -- GEOTECHNICAL GROUP

Seattle, Washington

September 30, 2010

Materials for this talk are based on work by I. M. Idriss and R. W. Boulanger

Idriss & Boulanger (2008). "Soil Liquefaction During Earthquakes." Monograph MNO-12, EERI.

Idriss & Boulanger (2010). "SPT-based liquefaction triggering procedures. "Report UCD/CGM-10/02, University of California, Davis, CA.

The "Peck Lecture", which was presented at ASCE's GeoFlorida Conference on February 21, 2010 by I. M. Idriss.

The full text of the "Peck Lecture" (by I. M. Idriss and R. W. Boulanger) is to be published in the Geotechnical Journal of ASCE in 2011 or 2012, depending on the length of the review process.

2

PECK AWARD

The Ralph B. Peck Award recognizes an individual's contributions to the geotechnical engineering profession through the publication of a thoughtful, carefully researched case history or histories, or the publication of recommended practices or design methodologies based on the evaluation of case histories.

Case Histories have always played a strong role in geotechnical engineering. They have been an essential means for:

improving understanding;

Calibrating analytical procedures;

Designing & interpreting physical model tests; and

developing semi-empirical procedures

Under static as well as during earthquake and post-earthquake loading conditions.

ROLE OF CASE HISTORIES

3

SIGNIFICANT EARTHQUAKES SINCE 19601962 Mexico City1964 ALASKA1964 NIIGATA1966 Parkfield 1967 Caracas1968 Tokachi-Oki1971 SAN FERNANDO1975 Oroville1975 Haicheng1976 Gazli (USSR)1976 Tangshan1978 Miyagiken-Oki1978 Santa Barbara1978 Tabas1979 Coyote Lake1979 IMPERIAL VALLEY1980 Livermore

1992 Petrolia1992 Landers1992 Big Bear1994 NORTHRIDGE1995 KOBE1999 KOCAELI1999 CHI-CHI1999 Duzce2001 Bhuj2001 Nisqually 2004 Niigata2010 Chile

1980 Mammoth Lake1982 Miramichi1983 Coalinga1985 Chile1985 MEXICO CITY1985 Nahani1986 NORTH PALM SPRINGS1987 WHITTIER-NARROWS1988 Armenia1988 Saguenay1989 LOMA PRIETA1990 Manjil1990 Philippine1991 Costa Rica1991 Sierra Madre1992 Turkey1992 Joshua tree

OUTLINE OF THIS TALK

Case Histories of large deformationsinvolving soft cohesive soils:

Case Histories involving liquefaction of cohesionless soils:

4

LIQUEFACTION OF COHESIONLESS SOILS

Examples of Surface Evidence of Liquefaction

1978 Miyagiken-Oki earthquake


5

1964 Niigata earthquake (photo: NISEE)


1971 San Fernando earthquake (photo: California DWR)


6


1999 CHI-CHI earthquake


Information needed for each case history

1. Site information:i. Location, adjacent topography;ii. Adjacent physical features;iii. Surface [Evidence/No Evidence] of liquefaction.

2. Subsurface information: i. Borings, samples – methods used;ii. Water table measurements;iii. Standard penetration tests – details used;iv. Cone penetration resistance data;v. Shear wave measurements – method(s) used.

3. Earthquake & earthquake ground motions informationi. Mw, distance, nearby recordings, site "classification".

7


Use of liquefaction case histories started in 1968. At that time, there were only 23 cases with observed surface evidence of liquefaction and 12cases with no observed evidence of liquefaction.

These case histories were used in the development of the Seed-Idriss simplified liquefaction procedure, which was published in the Journal of ASCE's SM&FE Division in 1971.


Since then, the number of cases has dramatically increased.

While in 1968 correlation was made to relative density and SPT blow count only, correlations are now made with:

SPT blow count; CPT tip resistance, and Vs, shear wave velocity.

More recently, correlations with dilatometer measurements have been proposed.

8

1 60 N E R B S mN C C C C C N

. , vM 7 5 1 1 60csCRR f N

Analysis framework

CYCLIC RESISTANCE RATIO (CRR)[Framework is similar for SPT, CPT, or Vs correlations]

1 1 160cs 60 60N N N . , ,

vcM 7 5 1 1 60CRR f N FC


. , vM 7 5 1 1 60csCRR f N

Analysis framework

Cyclic resistance ratio (CRR)[Framework is similar for SPT, CPT, or Vs correlations]

1 1 160cs 60 60N N N . , ,


CN = f('v; DR; FC)

CR = f(depth; rod stick-up length)

9

v

v dM

v

a rCSR 0 65

max, .

Analysis framework

Earthquake-induced

CYCLIC STRESS RATIO (CSR)

based on using the Seed-Idriss (1971) Simplified Procedure

rd = f(depth; ground motion characteristics; dynamic soil properties)

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

vM , ' vo max dM 7.5

vo

CSR a r 1CSR 0.65

MSF ' MSF

10

Cyclic triaxial test results for clean Fraser Delta sand showing cyclic stress and CRR to cause 3% shear strain in 10 uniform cycles at DR of 31-72% and

effective consolidation stresses of 50-400 kPa (data from Vaid & Sivathayalan 1996).

EFFECTS OF INITIAL EFFECTIVE VERTICAL STRESS, 'v

Cyclic stress to cause 3% strain in 10 uniform cycles versus effective consolidation stress in ICU cyclic triaxial tests on Fraser Delta sand

(data from Vaid & Sivathayalan 1996)


11

Effects of 'v

v

v

M. ' vo max dM 7.5 , ' 1 atm

vo

CSR a r 1 1CSR 0.65

MSF K ' MSF K

Framework includes 5 functions that describe fundamental aspects of dynamic site response, penetration testing, and soil behavior:

rd = f(depth; ground motion characteristics; dynamic soil properties)

CN = f('v; DR; FC)


K = f('v; DR; FC)

MSF = f(ground motion characteristics; DR; FC)

These functions should be based on a synthesis of experimental and theoretical methods, as they guide the application to conditions outside those that are represented in the case history database.

Analysis framework

12

Many questions have been raised over the years regarding evaluation of liquefaction potential during earthquakes.

I will attempt to address in this presentation 4 of the most recurring questions.



Corrected standard penetration, (N1)60

0 10 20 30 40

Cyc

lic s

tres

s ra

tio

0.0

0.1

0.2

0.3

0.4

0.5

0.6Curves derived by

FC5%

Seed & Idriss (1982)

Seed et al (1984) & NCEER/NSF Workshops (1997)

Idriss & Boulanger (2004)

Seed (1979)

Cetin et al (2004)

1

2

3

5

3

21

5

4

4

13

QUESTIONS RAISED

Q-2. Can we treat these differences as "epistemic" uncertainty and hence can use all models with "assigned weights"?

Q-3. Can we use site response analyses to obtain CSR or do we have to always use the simplified stress ratio equation?

Q-4. How should we treat liquefaction at depths exceeding those included in the liquefaction case histories?

Q-1. Why are the published curves of CRR versus (N1)60 or versus (N1)60cs different, depending on whose model is implemented?

QUESTION No. 1

Q-1. Why are the published curves of CRR versus (N1)60 or versus (N1)60cs different, depending on whose model is implemented? In particular, why is the Cetin et al correlation so much lower than the other correlations?

Equivalent clean sand corrected standard penetration, (N1)60cs

0 10 20 30 40

CR

R

0.0

0.1

0.2

0.3

0.4

0.5

0.6Curves derived by 3

5 4Seed et al (1984) & NCEER/NSF Workshops (1997)


Cetin et al (2004)

3

4

5

14

QUESTION No. 1

The best way to address this question is to examine each model in terms of how the interpretations were made for those case histories that control the position of the correlation.

Specifically, it is essential that the derived liquefaction triggering correlation for M = 7.5 and 'v = 1 atm be supported by the case histories with 'v close to 1 atm.

Differences in the treatment of key case histories near 'v = 1 atm (where differences in CN and K are smallest) were found to be the primary cause of differences in the correlations.


. , vM 7 5 1 1 60csCRR f N

Cyclic Resistance Ratio

Cyclic resistance ratio (CRR)[Framework is similar for SPT, CPT, or Vs correlations]

1 1 160cs 60 60N N N . , ,


CN = f('v; DR; FC)


15

Where the functions are

v

v

M. ' vo max dM 7.5 , ' 1 atm

vo

CSR a r 1 1CSR 0.65

MSF K ' MSF K

Shear stress induced by theearthquake ground motions

Sensitivity of case history interpretation to MSF

16

0 10 20 30 40 50

(N1 )60

16

12

8

4

0

Dep

th b

elo

w g

rou

nd

su

rface (

m)

Liquefaction

Marginal

No liquefaction

0 0.2 0.4 0.6 0.8

CSRM=7.5,=1

16

12

8

4

0

5 6 7 8 9

M

16

12

8

4

0

Dep

th b

elo

w g

rou

nd

su

rfa

ce (

m)

0 20 40 60 80 100

FC (%)

16

12

8

4

0

Effects of duration

Earthquake moment magnitude, M

5 6 7 8

Mag

nit

ud

e sc

alin

g f

acto

r, M

SF

0.5

1.0

1.5

2.0

2.5

Cetin et al (2004)


Seed et al (1984)

17

Effects of 'v

v

v

M. ' vo max dM 7.5 , ' 1 atm

vo

CSR a r 1 1CSR 0.65

MSF K ' MSF K

Sensitivity of case history interpretation to K


K relations recommended by Youd et al (2001) for a relative density of40, 60 and 80% (solid lines) and relation used by Cetin et al (2004)

Vertical effective stress, 'v (atm)

0 1 2 3

K

0.0

0.5

1.0

1.5

Cetin et al (2004)

Youd et al (2001);DR = 40, 60 & 80%

18



0 1 2 3

K

0.0

0.5

1.0

1.5 Boulanger & Idriss (2004);DR = 40, 60 & 80%

K relations recommended by Boulanger and Idriss (2004)for a relative density of 40, 60 and 80%



0.0 0.5 1.0 1.5 2.0

K

0.0

0.5

1.0

1.5

Boulanger & Idriss (2004); DR = 60

Youd et al (2001); DR = 60

Cetin et al (2004)

19



0.6 0.8 1.0 1.2 1.4 1.6

K

0.8

0.9

1.0

1.1

1.2

Boulanger & Idriss (2004); DR = 60

Youd et al (2001); DR = 60

Cetin et al (2004)

Case histories of Liquefaction/ No Liquefactionpublished by Cetin et al (2004)

Effective vertical stress, 'v (psf)

0 500 1000 1500 2000 2500 3000

Cu

m. D

istr

ibu

tio

n (

%)

0

20

40

60

80

100

0.8 atm

1.2 atm

1 atm

Values of 'v as listed in Cetin et al (2004) for

the "liquefaction" & "marginal" case histories

0.65 atm

20


(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4Cetin et al (2004)

M = 7.5; 'v = 1 atm

12

3

45

67

89

1011

Triangles: 1984 cases; Circles: 2000 cases;Squares: Kobe proprietary cases.Filled-in symbols: liquefaction;Open symbols: no liquefaction;Cyan symbol: marginal.

Cases for 'v = 0.65 to 1.5 atm

Data and parameters fromCetin et al (2004); Points 1 -- 11identified for further examinationas described in text.


Point identified in next figure Site name Earthquake

1 Miller Farm CMF-10 1989 Loma Prieta earthquake; M = 6.9

2 Malden Street, Unit D 1994 Northridge earthquake; M = 6.7

3 Kobe #6 1995 Hyogoken-Nambu (Kobe) earthquake; M = 6.9



6 Rail Road #2 1964 Niigata earthquake; M = 7.6

7 Port of Oakland POO7-2 1989 Loma Prieta earthquake; M = 6.9


9 Panjin Chemical Fertilizer Plant

1975 Haicheng earthquake; M = 7.0

10 Shuang Tai Zi River 1975 Haicheng earthquake; M = 7.0

11 San Juan B-3 1974 Argentina earthquake; M = 7.4

Sites identified for further examination because they dictate the location of the liquefaction triggering curve for M = 7.5 & 'v = 1 atm

21
















misclassified cases

Point 1 – Miller Farm CMF-10

Profile across the failure zone at the Miller (south side of Pajaro River) during the 1989 Loma Prieta Earthquake (Holzer et al. 1994)

22

Cetin et al (2004)

From Cetin et al (2000)

Geotechnical Engineering Research Report No. UCB/GT-2000/09

Point 2 – Malden St.Unit D

Point 2: Malden Street , Unit D

Profile across the failure zone at the Malden Street site during the 1994 Northridge Earthquake (Holzer et al. 1998)

23

Expanded profile across the failure zone (Holzer et al. 1998)[additional details in Bennett et al. 1998]

Point 2: Malden Street , Unit D

Point 3 – Kobe proprietary site 6

Original table from Tokimatsu (2010)

From Cetin et al (2000)

Geotechnical Engineering Research Report No.

UCB/GT-2000/09

24

Point 10 – Shuang Tai Zi River


From original source: Shengcong & Tatsuoka (1984)

25


From Seed et al (1984)

Points 1, 2, 3 & 10 were designated as "No Liquefaction" by the original investigators of these sites; Cetin et al (2004) listed these as "Liquefaction" sites.

Point 1 Miller Farm CMF 10 'v 0.70 atm

Point 2 Malden Street 'v 1.2 atm

Point 3 Kobe No. 6 'v 0.68 atm

Point 10 Shuang Tai Zi R. 'v 0.69 atm


26


(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4Cetin et al (2004)

M = 7.5; 'v = 1 atm

12

3

45

67

8

9

1011



Data and parameters fromCetin et al (2004); Points 1, 2, 3 & 10were designated as "No Liquefaction"by the original investigators ofthese sites; Cetin et al (2004) listed these as "Liquefaction" sites .


0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

rd values from summary tables in Cetin et al (2004)

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

r d v

alu

es

com

pute

d u

sin

g C

etin

et

al's

eq

uat

ion

(on

ly fo

r ca

ses

with

out s

ite r

esp

on

se c

alcu

latio

nss

) Issue: The rd values computed using the Cetin et al (2004) equation do not agree with the rd values they usedin processing the case histories.

Discrepancy between rd values used in the Cetin et al (2004) database and the rd

values computed using their referenced rd equation

27
















rd


(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4

12

345

67

89

10

11

Cetin et al (2004)M = 7.5; 'v = 1 atm



Data and parameters fromCetin et al (2004); CSR for Points3, 4, 6, 9. 10 & 11 recalculatedusing equation for rd in Cetin et al

(2004) in lieu of their listed values.

28
















SPT data not included

Point 4 – Kobe Proprietary Site No. 7 (from Cetin et al (2000)

Point 4(Kobe No. 7 site)

29


Point 4 (Kobe No. 7 site) 'v 0.8 atm


Selection of a representative (N1)60 for Point 4 (Kobe No. 7 site)Average 'v 0.86 atm

Avg

depth

(m)

Depth to

GWT (m) vc (kPa) 'vc (kPa) (Nm) (N1)60 CB CE CN CR CS FC (%) (N1)60,cs

3.3 3.2 62 60 8 10.4 1 1.22 1.26 0.85 1 0 10.4

4.3 3.2 82 71 21 28.2 1 1.22 1.16 0.95 1 0 28.2

6.3 3.2 124 93 32 37.7 1 1.22 1.02 0.95 1 12 39.8

7.3 3.2 144 104 23 25.6 1 1.22 0.96 0.95 1 0 25.6

8.3 3.2 165 114 21 23.4 1 1.22 0.92 1 1 0 23.4

Averages:

5.8 113 87 18.3 21.9 Average= 0 21.9

30


(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4

12

34 5

67

89

10

11

Cetin et al (2004)M = 7.5; 'v = 1 atm



Data and parameters fromCetin et al (2004); CSR & (N1)60 for

Point 4 recalculated to includea sublayer below the water tablewith N = 8, which had not beenused by Cetin et al (2004).


(N1)60cs

0 10 20 30 40

CS

R (

ad

just

ed t

o M

= 7

.5 &

' v

= 1

atm

)

0.0

0.1

0.2

0.3

0.4

12

34 5

67

89

10

11

Cetin et al (2004)M = 7.5; 'v = 1 atm




Point 4 recalculated to includea sublayer below the water tablewith N = 8, which had not beenused by Cetin et al (2004).

31

Point 6 – Rail Road-2 (from Cetin et al (2000)


10 12 14 16 18 20 22

Average total unit weight (kN/m3)

12

10

8

6

4

2

0

Dep

th b

elow

gro

und

su

rfac

e (m

)

Idriss & Boulanger (this study)

Cetin et al (2004)

Seed et al. (1984), plus

Averages of all values

Kobe proprietary (Tokimatsu)

32


(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4

1

23

45

678

9

10

11

Cetin et al (2004)M = 7.5; 'v = 1 atm




Points 1 -- 11 recalculated using unit weights described in text.

(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4

12

34 5

67

89

10

11



Idriss & Boulanger (2004)M = 7.5; 'v = 1 atm NCEER/Youd (2001)

M = 7.5; 'v = 1 atm

Data and parameters fromCetin et al (2004); Changes toPoints 1 -- 11 described in text.

33


10 12 14 16 18 20 22

Average total unit weight (kN/m3)

12

10

8

6

4

2

0

Dep

th b

elow

gro

und

su

rfac

e (m

)Idriss & Boulanger (this study)

Cetin et al (2004)

Seed et al. (1984), plus

Averages of all values

Kobe proprietary (Tokimatsu)
















Low total unit weights

34

(N1)60cs

0 10 20 30 40

CS

R (

adju

sted

to

M =

7.5

&

' v =

1 a

tm)

0.0

0.1

0.2

0.3

0.4

1

23

45

67

89

10

11



Cetin et al (2004)M = 7.5; 'v = 1 atm

Idriss & Boulanger (2004)M = 7.5; 'v = 1 atm

Data and parameters fromCetin et al (2004); Changes toPoints 1 -- 11 described in text.

Conclusions re: Question No. 1

• The Cetin et al. triggering correlation, if it were updated after correcting the above problems, would thus be expected to move close to the Idriss-Boulanger correlation at overburden stresses of 0.65-1.5 atm.

• This would also cause the Cetin et al. K relationship to become flatter because it is regressed as part of their analyses and higher CRR values at higher confining stresses would dictate a flatter Ks relationship.

Q-1. Why are the published curves of CRR versus (N1)60 or versus (N1)60cs different, depending on whose model is implemented? In particular, why is the Cetin et al correlation so much lower than the other correlations?

35

• The combination of these changes would be expected to reduce the degree to which the Cetin et al. procedure predicts significantly smaller CRR values than the other liquefaction triggering correlations as depth increases.

• Until these issues are addressed, however, the Cetin et al. procedure should not be used.


Question No. 2

Q-2. Can we treat these differences as "epistemic" uncertainty and hence can use all models with "assigned weights"?

No, we should not treat these differences as "epistemic" uncertainty and hence can use all models with "assigned weights".

The examination I just summarized emphasizes the need to fully examine any model before it is adopted for use.

36

Question No. 3


The answer is – it depends.

37

Shear wave velocity (m/sec)

0 200 400 600 800

Dep

th (

m)

0

20

40

60

80

100

120

140

160

Vs profile used in 1990

Vs profile used

in 1993 and 1996

1996

1993

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

(g

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

damping = 5 percent

Calculated Motion using 1990 Vs profile

Recorded Motion at Treasure Island

Rock Outcrop (Yerba Buena Island)



38

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

(g

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

damping = 5 percent

Spectral values for motionrecorded at Treasure Island

Spectral values calculated using

recording at Yerba Buenaas input motion

39

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

(g

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

damping = 5 percent

Spectral values for motionrecorded at Treasure Island

Spectral values calculated using

recordings at other rock sitesin the Bay Area as input motions


Maximum shear stress (kPa)

0 10 20 30 40

Dep

th (

m)

0

5

10

15

20

Maximum shear stresses calculated using:



average shear stresses for all cases

40

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

/ P

GA

0.0

0.5

1.0

1.5

2.0

2.5

3.0

damping = 5 percent

Target spectrum -- M = 6.9 at 80 km

Spectrum compatible motion -- SYN1

Spectrum compatible motion -- SYN2


0 10 20 30 40

Dep

th (

m)

0

5

10

15

20





Input: SYN1

41


0 10 20 30 40D

epth

(m

)0

5

10

15

20





Input: SYN2

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

/ P

GA

0.0

0.5

1.0

1.5

2.0

2.5

3.0

damping = 5 percent

Target spectrum -- pre-NGA

Target spectrum -- NGA

42

Period (sec)

0.01 0.1 1 10

Sp

ectr

al a

ccel

erat

ion

/ P

GA

0.0

0.5

1.0

1.5

2.0

2.5

3.0

damping = 5 percent

Target spectrum -- NGA

Spectra -- synthetic time series


0 10 20 30 40

De

pth

(m

)

0

5

10

15

20


NGA-compatible time seriesas input motions


43


0 10 20 30 40D

epth

(m

)0

5

10

15

20


NGA-compatible time seriesas input motions


average shear stresses synth time series

Using simplified equation (F = ma):

surfmax v d

surf

ar

g

a 0.16g

44

Stress reduction coefficient, rd

0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Dep

th b

elo

w g

rou

nd

su

rfac

e (m

)0

4

8

12

16

20

24

28

M = 7½ M = 8Magnitude: M = 5½ M = 6½

Average of Range Publishedby Seed & Idriss (1971)

M = 6.9


0 10 20 30 40

De

pth

(m

)

0

5

10

15

20





Calculated usingrd for M = 6.9

45


• Use of an appropriate rd is adequate for most cases.

• For site response studies, you need to use at least 7 different rock outcrop motions.


Q-4: How should we evaluate liquefaction at depths that exceed those represented in liquefaction case histories?

Two critical parameters affecting liquefaction potential with depth are CN and K.

Studies at Perris Dam provide valuable data on CN at large depths

Studies at Duncan Dam provide a valuable check on the complete liquefaction analysis procedure for large depths.

Question No. 4

46

A critical parameter affecting liquefaction potential with depth is the value of CN. Boulanger and Idriss (2004) recommended:

m

aN

vo

1 60

PC 1.7

m 0.784 0.0768 N

Note that m = ½, originally derived by Liao & Whitman has been extensively used, but it can produce unreasonably low CN values as the depth increases.

The investigations carried out at Perris Dam (CDWR 2005, Wehling and Rennie 2008) are very helpful is assessing the value of the exponent m as a function of denseness.

Perris Dam and CN

Aerial photo and boring locations at Perris Dam (Wehling & Rennie 2008)

47

SPT data by location and percentile groupings (Wehling & Rennie 2008)

0 20 40 60 80SPT (N1 )60

0

0.2

0.4

0.6

0.8

Exp

on

ent m

0 20 40 60 80SPT (N1 )60,CS

0

0.2

0.4

0.6

0.8

Exp

on

ent m

CN = (Pa /'v )m

Idriss & Boulanger (2008)[using (N1)60 as input]


Perris dam foundation(Wehling & Rennie 2008)

Perris dam foundation(Wehling & Rennie 2008)

CN = (Pa /'v )m

48

Overburden normalization factor CN: (a) dependence on denseness, and (b) simpler approximations often used at shallower depths.

0 0.5 1 1.5

CN

10

8

6

4

2

0

Ve

rtic

alef

fect

ive

stre

ss,

' v/P

a

(N1)60cs=40

(N1)60cs=30

(N1)60cs=20

(N1)60cs=10

(N1)60cs=4

0 0.5 1 1.5

CN

2

1.5

1

0.5

0

Ver

tica

leffe

ctiv

est

ress

, ' v

/Pa

(a) (b)

(N1)60cs=4

(N1)60cs=30

Liao & Whitman (1986)CN = (Pa /'v )0.5

The investigations carried out at Duncan Dam (Special collection of papers in the Canadian Geotechnical Journal, 1994) are helpful in assessing the application of liquefaction triggering procedures to large depths.

Duncan Dam

49

Frozen sand samples obtained from Unit 3c at the toe, and tested at confining stresses of 2 to 12 atm.

Duncan Dam

Table 5.2. Summary of SPT and laboratory test data for Duncan Dam SPT data DSS tests Triaxial tests Conversion to 'v = 1 atm 'v (kPa)

CN N60 (N1)60 (N1)60cs Lab CRRN=10

Field CRRM=7.5

Lab CRRN=10

Field CRRM=7.5

Field CRRM=7.5

K Field CRRM=7.5,=1

200 0.70 16.4 11.5 11.6 0.14 0.118 0.169 0.121 0.120 0.93 0.128 400 0.50 26.5 13.3 13.4 0.149 0.126 0.171 0.123 0.124 0.86 0.145 600 0.42 34.0 14.1 14.2 0.143 0.121 0.168 0.120 0.120 0.81 0.149 1200 0.30 49.1 14.7 14.8 -- -- 0.170 0.122 0.122 0.73 0.168

Notes: (1) Original data from Pillai and Byrne (1994). (2) Average ratio of CRRDSS/CRRTX = 0.85 is used to convert triaxial test results to field simple shear conditions. (3) Cyclic strengths multiplied by 0.937 to convert from 10 to 15 equivalent uniform cycles (based on slope of

CRR versus number of uniform cycles curves). (4) Cyclic strengths multiplied by 0.90 to convert from 1D to 2D cyclic loading conditions. (5) Final value for field CRRM=7.5 taken as average of strengths from DSS and Triaxial tests.

SPT-based prediction of CRRM=7.5 versus depth (confining stress) depends on combination of triggering curve, CN, and K.

Duncan Dam

Corrected standard penetration, (N1)60

0 10 20 30 40

Cyc

lic s

tres

s ra

tio

0.0

0.1

0.2

0.3

0.4

0.5

0.6Curves derived by

FC5%

Seed & Idriss (1982)

Seed et al (1984) & NCEER/NSF Workshops (1997)


Seed (1979)

Cetin et al (2004)

1

2

3

5

3

21

5

4

4

50

Pillai & Byrne (1994) used the Seed et al. (1984) triggering curve, in-situ SPT data, and laboratory test data on frozen sand samples to derive site-specific CN and K relationships.

Duncan Dam

0 0.2 0.4 0.6 0.8 1 1.2

CN

12

10

8

6

4

2

0

Ver

tical

effe

ctiv

est

ress

, ' v

/Pa

Boulanger &Idriss (2004):(N1 )60=10(N1 )60=20

Liao & Whitman (1986)

Pillai & Byrne (1994)

0 0.2 0.4 0.6 0.8 1 1.2

K

12

10

8

6

4

2

0

Ver

tical

effe

ctiv

est

ress

, ' v

/Pa

(a) (b)

Boulanger &Idriss (2004):

(N1 )60=10(N1 )60=20

Hynes & Olsen(1999);f = 0.722

Pillai & Byrne(1994)

Kayen etal (1992)

CRRM=7.5 predicted using the Pillai & Byrne (1994) site-specific relationships with the Seed et al. (1984) triggering curve.

Duncan Dam

0 10 20 30 40 50 60

SPT N60 values

12

10

8

6

4

2

0

Ve

rtic

al e

ffect

ive

str

ess

(atm

)

0 10 20 30

(N1 )60

12

10

8

6

4

2

00 0.1 0.2 0.3

CRRM=7.5

12

10

8

6

4

2

0

Computed using relations by Pillai & Byrne (1994)

CRRM7.5 from TX & DSS tests on frozen samples (Pillai & Byrne 1994)

Duncan Dam - Unit 3c:(Pillai & Stewart 1994)

51

Duncan Dam

0 10 20 30 40 50 60

SPT N60 values

12

10

8

6

4

2

0V

ert

ical

effe

ctiv

e s

tres

s (a

tm)

0 10 20 30

(N1 )60

12

10

8

6

4

2

00 0.1 0.2 0.3

CRRM=7.5

12

10

8

6

4

2

0

Computed using relations by Idriss & Boulanger (2008)



CRRM=7.5 predicted using the Idriss & Boulanger (2004, 2008) liquefaction triggering procedures.

Duncan Dam

0 10 20 30 40 50 60

SPT N60 values

12

10

8

6

4

2

0

Ve

rtic

al e

ffec

tive

stre

ss (

atm

)

0 10 20 30

(N1 )60

12

10

8

6

4

2

00 0.1 0.2 0.3

CRRM=7.5

12

10

8

6

4

2

0

Computed using relations by NCEER/NSF (Youd et al. 2001)



CRRM=7.5 predicted using the NCEER/NSF (Youd et al. 2001) liquefaction triggering procedures.

52

Duncan Dam

0 10 20 30 40 50 60

SPT N60 values

12

10

8

6

4

2

0V

ert

ica

l eff

ectiv

e st

ress

(at

m)

0 10 20 30

(N1 )60

12

10

8

6

4

2

00 0.1 0.2 0.3

CRRM=7.5

12

10

8

6

4

2

0

Computed using relations by Cetin et al. (2004)



CRRM=7.5 predicted using the Cetin et al. (2004) liquefaction triggering procedures.

Cetin et al. (2004) and Moss et al. (2006) used the same statistical analysis procedures to regress K from SPT and CPT case histories, respectively.

Regressing K from case histories

0 2 4 6 8 10Effective consolidation stress (atm)

0

0.5

1

1.5

K

Moss et al. (2006): From Bayesian regressionof CPT-based liquefaction triggering database

15(N1 )60 = 5

25

Boulanger & Idriss (2004): From combinationof lab- & field-derived CRR-R correlations

Cetin et al. (2004): From Bayesian regressionof SPT-based liquefaction triggering database

53

Q-4: How should we evaluate liquefaction at depths that exceed those represented in liquefaction case histories?

CN describes how penetration resistance varies with confining stress, and it fundamentally depends not only on 'v but also on soil denseness.

For v > 2 atm, the Liao-Whitman (1986) or Kayen et al. (1992) relationships for CN, as adopted for the NCEER/NSF (Youd et al. 2001) procedures, can lead to a significant under-estimation of (N1 )60 values for denser soils.

For v > 2 atm, the Boulanger-Idriss (2004) relationship for CN produces more realistic (N1 )60 values for denser soils, as supported by calibration chamber test data, penetration theory, and field studies.


K describes a fundamental soil behavior that also depends on 'v and on soil denseness.

The K relationships regressed from case history data by Cetin et al. (2004) & Moss et al. (2006) are not justifiable and should not be used.

The K relationships by Boulanger & Idriss (2004) or Hynes & Olsen (1998) are reasonable options.

The procedures by Idriss & Boulanger were in good agreement with data for Duncan Dam. The NCEER/NSF (Youd et al. 2001) procedures with the Hynes-Olsen Krelationship under-estimated CRR for the larger depths.


54

Three recurring questions regarding assessment of liquefaction potential were addressed.

1. Why are the published curves of CRR versus (N1)60 or versus (N1)60cs different so different if they are based on largely the same case history data?

2. Can we treat these differences as "epistemic" uncertainty and hence can use all models with "assigned weights"?

1. Can we use site response analyses to obtain CSR or do we have to always use the simplified stress ratio equation?

2. How should we treat liquefaction at depth exceeding those included in liquefaction case histories?

Summary

presentation asce seattle imidriss

Documents