Liquefaction Evaluations at DOE Sites_1

7/30/2019 Liquefaction Evaluations at DOE Sites_1

1/45

1

LIQUEFACTION EVALUATIONS ATDOE SITES

M. Lewis, M. McHood, R. Williams, B. GutierrezOctober 25, 2011


2/45

Agenda

Background

Purpose and Objective

Liquefaction Methods

Site Evaluations

Aging

Conclusions

2


3/45

Background

3

Liquefaction at DOE Sites


4/45

Background

Liquefaction evaluations are required at allDOE sites

Methods have evolved over the years, butthere is currently only one consensusmethodology;

Youd et al., 2001

Two other methods have emerged in the lastfew years; Cetin et al., 2004

Idriss & Boulanger, 2008

4


5/45

Background

Youd et al., was the result of two workshops(NCEER/NSF) held in the late 1990s, culminatingin a NCEER report and a ASCE publication in2001. The method is widely used.

Cetin et al., was the result of several doctoraldissertations and evaluations at University ofCalifornia-Berkeley. It culminated in a ASCEpublication in 2004.

Idriss & Boulanger is the result of several MS &doctoral dissertations and evaluations atUniversity of California-Davis. It culminated inan EERI Monograph in 2008.

5


6/45

Background

There is currently ongoing discussion in theprofession regarding the Cetin et al., andIdriss & Boulanger methods.

There is no such discussion regarding Youd etal.

This presentation will present results from

each for comparison. We will also present results from the SRS site-

specific methodology for comparison to Youdet al.

6


7/45

Purpose & Objectives

7



8/45

Purpose & Objectives

The overall purpose is to present and showdifferences in each of the methodologies(Youd, Cetin, and Idriss & Boulanger) withrespect to liquefaction factor of safety (FS)

Comparisons will be shown of variousparameters along with some discussion

An added comparison will be made betweenthe SRS site-specific and Youd methodologiesto introduce a potential aging correction

8


9/45


9



10/45

Liquefaction Evaluation

Methods Youd et al., 2001

Only consensus liquefaction method NSF/NCEER Workshops in the 1990s

ASCE Geotechnical Journal October 2001 Cetin et al., 2004

Re-evaluated some key case histories ASCE Geotechnical Journal December 2004

Idriss & Boulanger 2008 EERI Monograph 12 (MNO-12) SRS site-specific, 2008

Results from site-specific laboratory testing

10


11/45


For this comparative evaluation the Seed & Idrisssimplified equation will be used to calculate theearthquake demand.

Each of the four methods will utilize the specificrecommendations of each method for the variousparameters (e.g., rd, MSF, CN, and K ).

The evaluation with the 3 methods will utilize resultsfrom the standard penetration test (SPT), using the

method-specific triggering relationship. The added comparison between the SRS and Youd

methods will utilize the triggering relationshipsdeveloped for the Cone Penetration Test (CPT).

11


12/45


Just a reminder, the Seed/Idriss simplifiedequation;

The safety factor against liquefaction isdefined as;

12

d

vo

vo

vo

ave rg

aCSR

'

max

'65.0

age7.5 KKKMSF

CSR

CRRFS

d

vo

vo

vo

ave rg

aCSR max''

65.0


13/45


Where;

CSR is the earthquake demand

CRR is the soils capacity (resistance or strength)

MSF the magnitude scaling factor

K a correction for static shear stress (set to 1 for thiscomparison)

K a correction for overburden pressure

Kage a correction for age (set to 1 for the comparison ofthe 3 methods)

vo and vo effective and total overburden pressures

13


14/45


Stress Reduction Coeff. (rd)

Cetin et al., lower at all

depths shown

Youd et al., varies with depth

Idriss & Boulanger changes

with earthquake M and depth

Cetin et al., changes with

depth, M, amax and Vs

Site response analysis

eliminates these differences

14


15/45


MSF Comparison

All three show similartrends

All three are equal at Mw =7.5

At Mw > 6.5, differences are

minimal

15


16/45


K Correction

Significant differences atshallow depths

Values vary withoverburden pressure andrelative density (DR)

Most level-groundevaluations are atoverburden pressures < 3.5to 4 tsf

16


17/45


SPT CN Correction

All relationships converge

at o

= 1 tsf

Relationships at o < 4 tsfare very similar

At o > 6 tsf, differences

can be important

17


18/45

SPT Triggering Relationships

18Idriss & Boulanger, 2010


19/45

SPT Triggering Relationships

19Adapted from Idriss & Boulanger, 2010

0.226

0.205

0.156


20/45

Triggering Relationships(most important difference)

CRR at (N1)60cs = 5

I/B:Y = 0.087/0.068 =1.28

C:Y = 0.048/0.068 = 0.71

CRR at (N1)60cs = 10

I/B:Y = 0.118/0.115 = 1.03 C:Y = 0.072/0.115 = 0.63


I/B:Y = 0.205/0.226 =0.91

C:Y = 0.156/0.226 = 0.69


I/B:Y = 0.48/0.6 = 0.8 C:Y = 0.338/0.6 = 0.56

20


21/45

Savannah River Site; F, Z, and K areas

21

Site Evaluations


22/45

SRS Generalized Profile

22

GWT varies by area;K 55 ft, F 80 ft, Z 55 ft


23/45

SRS Seismic Demand

Two earthquakes are utilized

Deterministic

Mw = 7.2, pga = 0.1g Charleston 50th (C50)

Probabilistic

Mw = 6.6, pga = 0.2g Design Basis Event (DBE)

23


24/45

SRS F-Area

Mw=7.2, pga=0.1g Mw=6.6, pga=0.2g

24

80

85

90

95

100

105

110

0.0 1.0 2.0 3.0 4.0 5.0 6.0

D

epth(ft)

Safety Factor

Youd I/B Cetin

80

85

90

95

100

105

110

0.0 1.0 2.0 3.0 4.0 5.0 6.0

D

epth(ft)

Safety Factor

Youd I/B Cetin


25/45

25


26/45

SRS Z-Area

Mw=7.2, pga=0.1g Mw=6.6, pga=0.2g

26

50

60

70

80

90

100

110

0.0 1.0 2.0 3.0 4.0 5.0 6.0

D

epth(ft)

Safety Factor

Youd I/B Cetin

50

60

70

80

90

100

110

0.0 1.0 2.0 3.0 4.0 5.0 6.0

D

epth(ft)

Safety Factor

Youd I/B Cetin


27/45

27


28/45


29/45

29


30/45

SRS Results

In general; Cetin results in lower FS

Youd and Idriss/Boulanger are comparable

Neglecting very high FS; I/B is about 9% of Youd with a ~ 20% for the C50 (Mw = 7.2)

I/B is about 12% of Youd with a ~ 21% for the DBE (Mw =6.6)

Cetin is about -44% of Youd with a ~ 24% for the C50 (Mw= 7.2)

Cetin is about -30% of Youd with a ~ 27% for the DBE (Mw= 6.6)

30


31/45

Paducah (PDGP)

31

Site Evaluations


32/45

Paducah Seismic Demand

Mw = 7.5, pga = 0.48g

32


33/45

Paducah Generalized Profile

33

GWT assumed at 10 ft


34/45

PDGP; SB-01, 02, 03, 05, 06

34

0

10

20

30

40

50

60

0.0 1.0 2.0 3.0

Depth(ft)

Safety Factor

Youd I/B Cetin


35/45

35


36/45

PGDP Results

In general, the results for each of the threemethods are much closer, however;

Cetin results in lower FS

Youd and Idriss/Boulanger are comparable

Overall;

Idriss/Boulanger is about -4% of Youd with a ~

26% (16 of 22 [73%] analyses within 20% of Youd) Cetin is about -35% of Youd with a ~ 22% results

(6 of 23 [26%] analyses within 20% of Youd)

36


37/45

Savannah River Site

37

Aging


38/45

Aging (SRS)

Compare Youd et al., (2001) to the SRSmethodology

SRS methodology based on site-specific

testing (CRR and K ); no attempt was madeto correct for disturbance

Most other parameters (CN, MSF, rd) followrecommendations of Youd

Difference in computed FS can be attributedto aging

Compare results for CPT in K-Area

38


39/45

Strength Gain vs Age

39Lewis et al., 2008


40/45

40

50

55

60

65

70

75

80

85

90

95

100

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Depth(ft)

FS

KC7

SRS DBE Youd DBE

KC


41/45

41

50

55

60

65

70

75

80

85

90

95

100

0.0 1.0 2.0 3.0 4.0 5.0 6.0

Depth(ft)

FS

KC7

SRS C50 Youd C50


42/45

42

50

55

60

65

70

75

80

85

90

95

100

0.60 0.80 1.00 1.20 1.40 1.60 1.80 2.00 2.20 2.40 2.60

Depth(ft

)

SRS/Youd (KC7)

C50/Youd C50 DBE/Youd DBE


43/45

Aging (SRS)

The results for CPT KC7 would indicate thefollowing;

For the DBE (Mw = 6.6, pga = 0.2g);

Ratio of SRS/Youd ranges from about 1.1 to 2.4, witha mean ~ 1.4 (say ~ 1.1 to 1.2 from 55 to 80 ft)

For the C50 (Mw = 7.2, pga = 0.1g);

Ratio of SRS/Youd ranges from about 1 to 2.3, with amean ~ 1.3 (say ~ 1.1 to 1.2 from 55 to 85 ft)

43


44/45

Strength Gain vs Age; SRS

44Adapted from Lewis et al., 2008


45/45

Conclusions

For the evaluations shown; Youd et al., is the only consensus liquefaction evaluation method

and is still recommended for use Site-specific correlations (SRS) can be extremely valuable

(expensive and time consuming) More than one tool (e.g., SPT, CPT) is recommended for

liquefaction evaluations Youd et al., and Idriss/Boulanger are comparable In general, Cetin et al., results in significantly lower FS than either

Youd et al., and Idriss/Boulanger

For SRS soils, an aging correction factor appears appropriatewhen using the Youd et al., relationship (which is for Holocenesoils)

Upcoming workshops specifically targeting resolution betweenIdriss/Boulanger and Cetin et al., methods would be very helpfulin resolving differences

Documents

Liquefaction Evaluations at DOE Sites_1