liquefaction hazard mapping -...

Liquefaction Hazard Mapping

Keith L. KnudsenSenior Engineering GeologistCalifornia Geological Survey –Seismic Hazard Mapping ProgramApril 20, 2006

Topics

Liquefaction hazard mapping (regional)

CGS approachOther approachesFuture CGS approaches

Comments on site-specific studiesQ & A

San Francisco “Zones of Required Investigation” for liquefaction &

landsliding (1:24,000)

Liquefaction - how does it work?

from University of Washington soil liquefaction web site

3 Ingredients for liquefactionLoose granular deposits Saturation Strong shaking

(Probabilistic PGA -10% exceedance in 50 years)

Consequences of liquefaction

Lateral spreadingSettlementFlow failureLoss of bearing capacityGround oscillation

Basis for CGS Liquefaction Zones of Required Investigation (ZORIs)Past occurrencesBoring logs (mainly SPT)

Geotechnical propertiesLoose sand & silt (Q deposits)Simplified procedure

GeologyUncompacted artificial fillHolocene deposits

Historical-high ground waterGround shaking (pga, magnitude)

Boring Log DatabaseOver 13,500 boringsOver 300,000 recordsOver 100 citiesBoring log info available for download on our web site! Northern California Database

Principal Parameters

4780

860

6042

80

8019

02000400060008000

10000

blow co

unt

dry de

nsity

grain si

ze

% mois

ture

void ra

tio

Geotechnical Parameter

Num

ber

of R

ecor

ds

Penetration resistance - Nfield to (N1)60 or (N1)60,cs

Resisting forces - CRR from (N1)60

Driving forces - CSR = 0.65(amax/g)(σ/σ’)rd

Factor of Safety - FS=CRR/CSRIf FS <1 then liquefaction (triggering) likely

Geotechnical Criteria for Liquefaction Zone –Simplified Procedure

Nfield to (N1)60

CRR from (N1)60

CSR = 0.65(amax/g)(σ/σ’)rd

FS=CRR/CSRIf FS<1 then liquefaction likely to be triggered

Geotechnical Criteria for Liquefaction Zone –Simplified Procedure

Hydrograph for a Santa Clara Valley monitoring well (modified from Figure 3-2, Reymers and Hemmeter, 2001)

Ground water - through time

Defining margin of liquefaction zone of required investigation

Qhf Qpf

Liquefaction zoneboundary

Top of Pleistocene

GW

saturated HolocenesedimentQpf

Qhf

Geologic Criteria for Liquefaction Zone

GEOLOGIC AGE PEAK GROUNDACCELERATION

HISTORICAL-HIGH GROUND

WATER

LATEHOLOCENE

(HISTORICALFLOODPLAINS,ESTUARIES)

>10% g <40 FT

HOLOCENE (< 11,000 YEARS) >20% g <30 FT

LATEPLEISTOCENE

(11,000-15,000YEARS)

>30% g <20 FT

Liquefaction Zoning - Issues & Limitations

Use available geotechnical data Any layer liquefies (triggers) -> area included in zoneZone is binary -> in or outHistorical-high ground water is usedFree faces and slopes – no special attention

Zones of Required

Investigation (liquefaction, landsliding,

surface rupture)

Guidelines and Criteria by CGS

SP 117SP 117SP 118SP 118

Important Publications from Southern Important Publications from Southern California Implementation CommitteesCalifornia Implementation Committees

(www.scec.org)(www.scec.org)

pga’sfrom reports:

(on CGS SHZP website)

Mode magnitude

anddistance

De-aggregated from PSHA

(in reports on web)

New CGS approaches to zoningPast occurrencesDeformation based – in areas with sufficient subsurface dataAreas with little boring data – grid based

Proximity to water body or streamAge of depositsAreas with free faces

(N1)60 min - Borings (only liquefiable textures)

Modern Latest Holocene

Holocene Latest Pleistocene

024

68

1012

141618

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

bor

ings

rep_age = Modern n = 39

Lognormal Distribution forModern

0

5

10

15

20

25

30

35

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

bor

ings

rep_age = Latest Holocene n = 70Lognormal Distribution forLatest Holocene

0

20

40

60

80

100

120

140

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

bor

ings

rep_age = Holocene n = 361

Lognormal Distribution forHolocene

0

1

2

3

4

5

6

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

bor

ings

rep_age = Latest Pleistocene n = 23Lognormal Distribution forLatest Pleistocene

(N1)60 - Layers (only liquefiable textures)

0

2

4

6

8

10

12

14

16

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

laye

rs

Modern

Lognormal Distribution for Modern

liquefiable textures only

0

5

10

15

20

25

30

35

40

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

laye

rs

Latest Holocene

Lognormal Distribution for LatestHolocene

liquefiable textures only

0

50

100

150

200

250

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

laye

rs

Holocene

Lognormal Distribution forHolocene

liquefiable textures only

0

5

10

15

20

25

30

35

40

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95

N160_min

# of

laye

rs

Latest Pleistocene

Lognormal Distribution for LatestPleistocene

liquefiable textures only

Modern Latest Holocene

Holocene Latest Pleistocene

(N1)60 - Layers (all textures)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100

N160_min

Cum

ulat

ive

Freq

uenc

y (%

)

age = Modern n = 153

age = Latest Holocene n = 254

age = Holocene n = 1651

age = Latest Pleistocene to Holocene n = 90

age = Latest Pleistocene n = 388

Lognormal Distribution for All

0 5 10 15 20 25 30 355

10

15

20

25

30

35

40

45

50

55

60

0.0250.050.10.20.30.40.50.60.70.80.911.11.21.31.41.51.6

N1,60,cs

CSR,

%Limiting shear strain, Wu 2002

5 10 15 20 25 30 35 40

N1,60,cs

5

10

15

20

25

30

35

40

45

50

55

60C

SR

,%

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

0.055

0.06

Volumetric strain, Wu 2002

Shear strain (%) - layers

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Shear Strain (%)

Cum

ulat

ive

Freq

uenc

y (%

)

age = Modern n = 29age = Latest Holocene n = 82age = Holocene n = 616age = Latest Pleistocene to Holocene n = 42age = Latest Pleistocene n = 150age = All n = 919

How good is the data? (Penetration tests)

Nm (ASTM D1586) Blow count Spt equivalent1 OD = 2.0" 29 28 272 OD < 2.5" 26 253 OD = or > 2.5" and < 3.0" 24 234 UNK or NULL 22 211 OD = 2.0" 20 192 OD < 2.5" 18 173 OD = or > 2.5" and < 3.0" 16 154 UNK or NULL 14 131 OD = 2.0" 12 112 OD < 2.5" 10 93 OD = or > 2.5" and < 3.0" 8 74 UNK or NULL 6 5

5 Sampler or hammer rejected; n160 is not calculated. 4 3 Force is not evaluated.

6

Data run prior to 4/20/00 or current data with "stealth" samplers or bad hammers. n160 calculated in error.

2 1

Rank of pen test

Type

of s

ampl

er re

cord

ed

Calculated force is betw een 5418 and 3150 pound-inches; n160 is

calculated.

Calculated force is > 5418 or < 3150 pound-inches; n160 is NULL

Force is assumed to be 4200 pound-inches, i.e. liquefy is applying the default mass and/or fall values of 140 lb. 30 in.; n160 is calculated.

Other approaches to regional liquefaction hazard mapping

Mw 7.4 Izmit, Turkey 1999 earthquake.

Mw 7.9 1906 San Francisco earthquake.

New Quaternary geologic mapping

USGS OFR 2006-10371:24,000

Quaternary map units (37 units)

New liquefaction susceptibility mapping

USGS OFR 2006-10371:24,000

Past occurrences

available USGS OFR 2000-444

Relationship between Quaternary map units & liquefaction susceptibility

Holzer et al., 2002

Holzer et al., 2002

M7.1 & M6.6 Earthquakes

LPI = Liquefaction

Potential Index

Liquefaction HazardHolzer et al., 2002

Site-specific investigations

From Seed et al., 2001

Site-specific investigationsConsult available mapsHistorical occurrences nearby?Age of sediment?Borings – collect & document quality dataGeologic interpretation – cross sections

Liquefaction triggering?Deformation?Consequences of deformation?Mitigation (& testing)Document & describe your approach, interpretations & results

Penetration Test Comparisons: Modified California Versus Standard Penetration Test

Jacqueline D.J. BottKeith L. KnudsenCharles R. Real

Review of N1,60 calculation

N1,60 = Nm.CE.CN.CR.CB. CS

Where Nm = measured blows (using SPT sampler)CE = Correction for hammer energy efficiencyCN = overburden correction factor (to 1 atm,)CR = correction for “short” rod lengthCB = Correction for borehole diameterCS = Correction for non-standard sampler

Conversion to SPT-equivalent from non-standard samplers

N=N’(WH/4200)(2.02-1.3752)/(OD2-ID2)(Burmister, 1948)

N=N’(WH/4200)(2/OD2)(LaCroix & Horn, 1973)

where N = SPT-equivalent blow countN’ = measured blow countWH = hammer mass (lbs) x fall distance (in)OD = outer diameter of non-standard sampler (in)ID = inner diameter of non-standard sampler (in)

Conversion factors for MCS to SPT-equivalent blowsUsing CGS Definition of MCS: ID = 2.0 in (1.875 in with liners) & OD = 2.5 in.

0.77 Burmister (1948)0.64 LaCroix & Horn (1973)

Other definition of MCS: ID = 2.5 in (2.4 with liners) & OD = 3.0 in

0.65 Burmister (1948)0.44 LaCroix & Horn (1973)

How?Compare consecutive samples (MCS & SPT) from same lithologic layer in same boring, that are within 5 ft of each other.Direct comparison of two such values cancels out factors often not reported by consultants such as hammer energy, borehole diameter, etc. Only overburden (and rod length for shallow samples) will be different so also compare N1,60’s

MLCLSM

MCS

SPT

<5 ft

MCS

MCS

SPT

SPT

<5 ft <5 ft

MCS-SPT MCS-MCS SPT-SPT

Consecutive samples taken in same lithologic layerin same boring, separated by 5 ft or less

MCS vs SPT - SFBA

0 20 40 60 80BLOW_COUNT

0

20

40

60

80

NM

0 20 40 60 80N1602

0

20

40

60

80

N16

01

Raw blows Converted to N1,60’s

MCS sample

SPT

sample

MCS Blows

SPT

Blow

s

N1,

60

N1,60 from MCS

N1,

60 f

rom

SPT

N=129

0

20

40

60

80

0 20 40 60 800

20

40

60

80

0 20 40 60 80Adjusted N1,60’s from MCS Blows

N16

0’s

fro m

SPT

Blow s

Y=0.45x + 9.16Do not use

MCS-SPT LS regression - SFBA

SPT vs SPT - SFBARaw blows Converted to N1,60’s

Deeper sample

Shallowe

rsa

mple

0 20 40 60 80NM1

0

20

40

60

80

NM

2

S P T B lo w s fo r S F B A d a ta ( 1 = d e e p e s t)

0 20 40 60 80N1601

0

20

40

60

80

N16

02

N 1 6 0 's f r o m S P T B lo w s fo r S F B A (1 = d

SPT Blows

SPT

Blow

s

N1,60

N1,

60

N=1121

Rogers (defines ModCal as 3” OD)

In Feb. or May, 2006 Environmental & Engineering Geoscience

Conclusions so far...When liquefaction is a concern USE SPTThere is a large scatter in blow count data - both for SPT and MCSCGS conversion from MCS to SPT-equivalent (N1,60) gives more consistent results for SFBA than for LA Basin. Is MCS defined differently in the two locations? Is this a function of the geology? Or related to something else?

New Probabilistic

Tools for Liquefaction Triggering Evaluation

SPT & CPT probabilistic triggering

Shear wave

velocity evaluation

– now probabilistic

Estimated horizontal

displacement

Free face ratio

Slope

T15

Earthquake magnitude

Distance to rupture

D5015

F15Youd et al. (2002) 6 parameter

Bardet et al. (1999) 4 parameter

Lateral Spreading

Predicting lateral spread displacements

Free facelog DH = -16.713+(1.532*M)-(1.406*logR*)-

(0.012*R)+(0.592*logW)+(0.540*logT15)+(3.413*log(100-F15))-(0.795*log(D5015+0.1mm))

Sloping groundlog DH = -16.213+(1.532*M)-(1.406*logR*)

(0.012*R)+(0.338*logS)+(0.540*logT15)+(3.413*log(100-F15))-(0.795*log(D5015+0.1mm))

(Youd et al., 2002)

“A Semi-empirical Model for the Estimation of Maximum Horizontal Displacement Due to Liquefaction-induced

Lateral Spreading”

Faris et al., 2003&

this conference

DPI

Hmax = exp(1.0443 ln(DPImax) + 0.0046 ln(α) + 0.0029 Mw)

Faris, 2003

Faris, 2003

Modified Chinese Criteria –being debated

From Seed et al., 2001

Predicting consequences

Liquefaction-related web sitesCalifornia Geological Survey – SHZP

http://www.conservation.ca.gov/cgs/shzp/New USGS/CGS liquefaction web site

http://sfgeo.wr.usgs.gov

San Francisco Bay Area susceptibility mapshttp://earthquakes.usgs.gov/regional/nca/qmap/

Association of Bay Area Governmentshttp://www.abag.ca.gov/bayarea/eqmaps/liquefac/liquefac.html

Soil Liquefaction – University of Washingtonhttp://www.ce.washington.edu/~liquefaction/html/main.html

Southern CA Implementation Committee doc. http://www.scec.org/resources/catalog/hazardmitigation.html#land

Liquefaction Engineering Resourceshttp://earthquake.geoengineer.org/liquefaction.html

DocumentsCGS SHZP evaluation reports – on web siteRecommended procedures for implementation of DMG Special Publication 117 - Guidelines for analyzing and mitigating liquefaction in CA [www.scec.org]Youd, T.L., and 20 others, 2001, Liquefaction resistance of soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils: Journal of Geotechnical and Geoenvironmental Engineering, 127(10), p. 817-833.Seed, R. B., Cetin, K. O., Moss, R. E. S., Kammerer, A. M., Wu, J.,Pestana, J. M. and Riemer, M. F., 2003, Recent advances in soil liquefaction engineering and seismic site response evaluation: International Conference and Symposium on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, paper SPL-2, San Diego, California, 71p. Idriss, I.M., and Boulanger, R.W., 2004, Semi-empirical procedures for evaluating liquefaction potential during earthquakes: 11th SDEE and 3rd ICEGE, Univ of CA, Berkeley, 2004