LIQUEFACTION PERFORMANCE CASE HISTORIES …or.nsfc.gov.cn/bitstream/00001903-5/148326/1/1000003698987.pdf · II International Conference on Performance Based Design in Earthquake

Paper No. 1.12

SECOND INTERNATIONAL CONFERENCE ON PERFORMANCE-BASED DESIGN IN EARTHQUAKE GEOTECHNICAL ENGINEERING

May 28-30, 2012 - TAORMINA (ITALY)

LIQUEFACTION PERFORMANCE CASE HISTORIES IN

CHRISTCHURCH AREA DURING THE 2010 AND 2011 EARTHQUAKES FROM CONE PENETRATION TEST AND SHEAR WAVE VELOCITY

Yan-Guo ZHOU 1, Tian LIANG 2, Dao-Sheng LING 3, Yun-Min CHEN4

ABSTRACT Recently two major earthquakes, the 2010 M7.1 Darfield and 2011 M6.3 Christchurch Earthquakes, occurred in Christchurch area, New Zealand and caused widespread liquefaction hazards. This paper compiles part of the liquefaction case histories in central areas of Christchurch city from both events, based on reconnaissance work conducted by the authors and the geotechnical factual data released by EQC of New Zealand, which contains high quality cone penetration test (CPT) and shear wave velocity (Vs) measurements. The case histories are rich in information because the subsurface conditions of affected areas are characterized in detail just several months before the occurrence of earthquake, the sites have experienced high levels of strong ground shaking from different earthquake source mechanisms, the liquefiable soils have appreciable fines content, and the surface manifestation of liquefaction was recorded and the ground damage of affected areas were carefully documented. As a result, the well defined Vs-based and CPT-based CRR charts for this event are presented for back-analyses of liquefaction triggering. These two events provide a wealth of data which will aid in the understanding of the nature and performance of liquefaction in the greater Christchurch area. Keywords: Earthquake, Christchurch, Liquefaction, Performance, Cone penetration test, Shear wave velocity.

INTRODUCTION On 4 September 2010 the Mw 7.1 Darfield Earthquake occurred in Christchurch, New Zealand, caused widespread seismic shaking that resulted in extensive damage to the Canterbury region. The epicentre of the 2010 Darfield Earthquake was approximately 40 km west of Christchurch, at an estimated focal depth of 10 km (Cubrinovski et al. 2010). On 21 February 2011, a devastating Mw 6.3 earthquake occurred in Christchurch as part of the aftershock sequence of the Mw 7.1 2010 Darfield earthquake. The epicenter was located approximately 10 km south-east of the Christchurch Central Business District (CBD), near the town of Lyttleton, at an estimated focal depth of 5.5 km. Large ground accelerations, both horizontal and vertical, were recorded in the Christchurch CBD and close surrounding areas (Cubrinovski et al. 2011). These two events caused extensive ground liquefaction in localized areas of Christchurch, and resulted in major ground settlement and lateral spreading with consequential building damage. Especially, the extent of liquefaction of the second event was significantly greater than that of the 2010 quake (Orense et al. 2011).

1 Associate Professor, MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Institute of Geotechnical Engineering, Zhejiang University, Hangzhou 310058, P. R. China. E-mail: [email protected] 2 Graduate Student, ditto, e-mail: [email protected] 3 Professor, ditto, E-mail: [email protected] 4 Professor, ditto, E-mail: [email protected]

II International Conference on Performance Based Design in Earthquake Geotechnical Engineering May 2012, 28-30 - Taormina, Italy

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This paper compiles part of the liquefaction case histories in central areas of Christchurch city (e.g., Avonside, Dallington, Wainoni, Burwood, Avondale, New Brighton, Bexley & Aranui and Richmond), based on reconnaissance work conducted by the authors and the geotechnical factual data released by EQC of New Zealand, which contains high quality cone penetration test (CPT) and shear wave velocity (Vs) measurement (EQC 2011). The subsurface conditions of these affected areas are characterized in detail after the Mw 7.0 September 3, 2010 Darfield earthquake. These sites have experienced high levels of strong ground shaking, the liquefiable soils have appreciable fines content, and the surface manifestation of liquefaction was recorded and the ground damage of affected areas were carefully documented. As a result, the well defined Vs- and CPT-based CRR charts for this event are presented for back-analyses of liquefaction triggering and post-liquefaction deformation performance.

REGIONAL TECTONICS, GEOMORPHOLOGY, AND SEISMICITY Christchurch lies on the edge of a technically seismically active region. Consequently, earthquakes are likely to occur at a magnitude that will have major impacts on the City. In addition, there are other areas of active faults close to Christchurch, including Pegasus Bay, Porters Pass, Ashley and Mt Grey, Hope and Lake Heron. Christchurch is situated on deep alluvial deposits, and sites are classified as level "D" (deep or soft soil) for structural purposes in the New Zealand design standards (NZS 1170.5:2004). There is a formation that underlies many areas in Christchurch called the Springston Formation and alluvial deposits within that formation include deposits of silt and sand that are highly susceptible to liquefaction (see Fig. 1(a)). In the vicinity of this formation the groundwater table is about 2 m to 3 m below the ground surface in the west and 0 m to 2 m below the ground surface in the east (Brown & Weeber 1992). In general, this area is highly prone to seismic liquefaction. Figure 1(b) shows the two earthquake sequences. The 2011 event is considered an aftershock because it was caused by a fault rupture within the zone of aftershocks that followed the September 2010 mainshock (NHRP 2011).

(a) Geological map (GNS, 1:250000) (b) Earthquake sequences of the two events

Figure 1. Seismic and geological conditions Ground Motions Characteristics during the Two Events Fig. 2 shows a typical comparison of the ground motion recordings at Shirley Library Station (SHLC), during the two events. Note that the duration of significant shaking at this station in the 2010 event is about 25-30 sec, while that of the 2011 event is approximately half of it. Figure 3 shows the PGA distributions of these two events. Because of the small magnitude and short source to site distance, the shaking of the second was approximately twice as strong as the first in the wider Christchurch CBD, and approximately three times


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in the near source region. Comparisons of the two events clearly illustrate the importance of source mechanism, attenuation pattern and local site effects on the damage conditions (Smyrou et al. 2011).

0 10 20 30 40 50-0.50

-0.25

0.00

0.25

0.50-0.50

-0.25

0.00

0.25

0.50

Acce

lera

tion,

g

Time, t(s)

Horizontal (S40W)Mw6.3, Feb 21, 2011

Horizontal (S40W)Mw7.1, Sep 4, 2011

Station: SHLC

0.1 1 10

0

1

2

3

40

1

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Frequency (Hz)

Horizontal (S40W)Mw6.3, Feb 21, 2011

Horizontal (S40W)Mw7.1, Sep 4, 2011

Spec

tral a

mpl

itude

(m/s

)

Station: SHLC

(a) Acceleration time history (b) Fourier amplitude spectrum of acceleration Figure 2. Strong motion recordings at station SHLC

(a) 2010 Mw 7.1 Darfield earthquake (b) 2011 Mw 6.3 Christchurch earthquake

Figure 3. PGA distributions for two events

SITE DESCRIPTION AND FIELD WORK The basis of a liquefaction field correlation is the observation of liquefaction or absence of liquefaction following a seismic event based on the observation of the manifestations of liquefaction at a particular location and the lack of manifestation at some other location, and the index test measurements of the suspect critical layer. These manifestations can take the form of sand boils or sand blows, lateral spreading, building tilting or settlement, ground loss, broken lifelines, etc.. Each in-situ test location (i.e., CPT, or Vs profile) was used to obtain one critical combination of earthquake induced cyclic stress ratio (CSReq) and normalized in-situ measurement (i.e., qclN or Vsl). Although many more CPT or Vs profiles are provided by EQC at earthquake sites, herein only those locations with CPT, Vs and borehole profiles simultaneously available are selected to compile the case histories. For clarity, the following sections are presented for Dallington Lower site, and the treatments are the same for other sites. Site Description and Field Works The subject area of Dallington Lower is a part of the suburb of Dallington located on the north east side of Christchurch and approximately 2 km from the Christchurch CBD. The area is low lying and topographically is typically flat. The Geology of the Christchurch Urban Area shows the subject area to be underlain by


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alluvial sand and silt overbank deposits of Holocene age. The extent of the subject area considered in this study is shown in Figure 4. In Dallington Lower, during the investigations, groundwater depths ranged from 3.2 m to 0.9 m below existing ground level. The geotechnical investigations commissioned by EQC were determined and located under direction from T&T. The investigations comprise: (a) Cone penetration tests (CPTs); (b) Machine drilled boreholes; (c) MASW geophysical testing; and (d) Laboratory testing including fines content and particle size distribution tests.

SHLC

PRPC

Dallington Lower

SHLC

PRPC

Dallington Lower

Figure 4. Subject area of Dallington Lower site (EQC 2011)

Geophysical Work and Vs interpretation The geophysical testing comprised Multichannel Analysis of Surface Waves (MASW) and was used to provide a shear wave velocity profile with depth. One copy of the geophysical testing results is presented in Figure 5. In selecting the critical value of normalized Vs in each Vs measurement at a specific borehole location, the critical value was taken as the average Vs over a 0.5 m interval to reduce potential biases.

BH3 locationBH3 location

Figure 5. Shear wave velocity profile in section BH-03 (EQC 2011)

Cone Penetration Testing Each CPT probe location was pre-dug by hand to between 800 mm and 1200 mm to mitigate the risk of unforeseen underground services being present at the selected investigation locations. The CPT rigs are pilot CPT and seismic CPT types. The typical CPT log data are shown in Figure 6.


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Figure 6. Typcial CPTu test profile in section BH-03 (EQC 2011)

INTERPRETATION OF IN-SITU DATA Case Selection The case selection in this study was to end up with a group of statistically independent data points. At any given site there can be multiple CPT and also corollary Vs logs to choose from. Selection of the critical layer is an important step in estimating the seismic strength of a particular soil deposit. The criterion for selection is finding the strata of soil that is the weakest-link-in-the-chain from a liquefaction perspective. Finding the weakest link requires observing the tip resistance and friction ratio in conjunction, with the addition information of soil classification via laboratory test. This is a matter of looking for the smallest continuous stretch of tip resistance with low friction ratio for CPT test, and the lowest Vs in sandy layers for Vs measurement. The most common approach for semi-empirical correlations to date has been to reduce the experience from individual sites to data points on a plot of CSR-qc1N (or Vs1) with each data point being associated with the occurrence or nonoccurrence of liquefaction. The key parameters involved in this procedure are explained as below. Cyclic Stress Ratio The dynamic stress that the critical layer experienced is determined using the simplified uniform cyclic stress ratio as defined by Seed & Idriss (1971):

av max vd

v v

0.65 aCSR rg

τ σσ σ

⎛ ⎞⎛ ⎞= = ⎜ ⎟⎜ ⎟′ ′⎝ ⎠⎝ ⎠

(1)

where τav = average equivalent uniform cyclic shear stress caused by the earthquake and is assumed to be 0.65 of the maximum induced stress; amax= peak horizontal ground surface acceleration; g = acceleration of gravity; σ′v = initial effective vertical (overburden) stress at the depth in question; σv = total overburden stress at the same depth; and rd= shear stress reduction coefficient to adjust for the flexibility of the soil profile. The NCEER committee recommends the following equations (Youd et al. 2001) for calculating average values of rd:


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1.0 0.00765dr z= − , mz 15.9≤ ， (2-a)

dr = z0267.0174.1 − , mzm 2315.9 ≤< , (2-b)

dr = z008.0744.0 − , mzm 3023 ≤< (2-c) where z = the depth below the ground surface in meters. Peak Ground Acceleration The event-specific estimation of peak horizontal ground acceleration (amax) is took according to the strong motion records available. The method of estimation is to take the average value of the PGA of the closest two strong motion recordings. The PGA and station information used in this paper are presented in Table 1.

Table 1. Strong motion records of two events Event 2010 Darfield 2011 Christchurch

PGA (mm/s/s) PGA (mm/s/s) Site Code Epicenter Distance (km) Vertical Horiz.Max

Epicenter Distance (km) Vertical Horiz.Max

SHLC 39 1130.5 1892.4 9 4907.2 3355.4 PRPC 41 3049.3 2303.7 6 15979.7 7106.3 HPSC 43 1263.5 1535.8 9 8410.2 2483.9

The duration weighting factor has been developed by a variety of different approaches (using cyclic laboratory testing and/or field case history data) by a number of investigators. The MSF relation produced by this re-evaluation was then expressed by Idriss (1999) as:

6.9exp 0.0584MMSF −⎛ ⎞= −⎜ ⎟

⎝ ⎠, ( 1.8MSF ≤ ) (3)

Then CSR values are corrected to “equivalent uniform cyclic stress ratio” (CSReq) for duration (or number of equivalent cycles) to CSRN, representing the equivalent CSR for a duration typical of an “average” event of MW = 7.5, as , 7.5 ,N eq M eq M MCSR CSR CSR MSF= == = (4) Stress Corrected Vs,1 In order to correct the effects of overburden stress for meaningful comparison in common practice (Andrus & Stokoe 2000), the measured Vs values should be further corrected in terms of the in-situ effective overburden stress (σ′v) as following:

/ 2

as1

v

n

s V sPV V C Vσ⎛ ⎞

= = ⎜ ⎟′⎝ ⎠ (5)

where CV = factor to correct in-situ measured velocity for σ′v, and a maximum CV value of 1.4 is applied at shallow depths; Pa= reference stress of 100 kPa. Normalized qc,1N Consistent procedures for selecting representative qc1N values from CPT soundings may be introduced by different individuals. Herein the guidelines proposed by Boulanger et al. (1997) are followed. Although cone


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penetration resistance is often just corrected for overburden stress (resulting in the term qc1), truly normalized (i.e., dimensionless) cone penetration resistance corrected for overburden stress (qc1N) can be given by

c c1c1N

a2 a2Q

q qq CP P

⎛ ⎞= =⎜ ⎟⎝ ⎠

(6)

where qc is the measured cone tip penetration resistance; CQ= (Pa/σ′v0)n is a correction for overburden stress; the exponent n is typically equal to 0.5; Pa is a reference pressure in the same units as σ′v (i.e., Pa = 100 kPa if σ′v is in kPa); and Pa2 is a reference pressure in the same units as qc (i.e., Pa2 = 0.1 MPa if qc is in MPa). A maximum value of CQ = 2 is generally applied to CPT data at shallow depths. The typical CPT and Vs profile are shown in Figure 7 for BH-03 in Dallington Lower site.

10

8

6

4

2

00 20 40 0 100 200100 150 200 250 0.1 0.2 0.3 0.4 0.5

Dep

th (m

)

FC (%) qc1N

Critical Layer

Soil Type

CSR7.5Vs1 (m/s)

2011

2010

SW

SP

GW

Fill

SP

ML

GW

GWT

Figure 7. Typical profiles in Dalinton Lower site (BH-3)

RESULTS & ANALYSIS Data for those locations where measurements of CPT or Vs coincided reasonably well with the suspected critical strata for Dallington Lower are tabulated in Table 2. The preliminary database of nine sites contains 47 datasets for each event, and 5 of them are judged as non-liquefaction with medium confidence. The poor-graded sand layers with D50 = 0.1-0.2 mm dominate the liquefied cases, while those non-liquefied are mainly gravelly sand or sand with gravel. The CPT case histories are shown in relation to both the deterministic and probabilistic liquefaction triggering curves (e.g., Robertson & Wride 1998; Moss, 2003; Idriss & Boulanger, 2006) in Figure 10. As shown in Figure 10, almost all liquefied cases fall in the range of 30<qc1N<125, and the qc1N value reaches over 175 for the non-liquefied cases. The datasets from the 2010 event spread more flatly along qc1N coordinate than those from the 2011 event, reflecting the different attenuation patterns of ground motions (Segou & Kalkan 2011). All three existing curves separate liquefied cases well, and the one proposed by Boulanger & Idriss (2006) performs better in low CSR zone.


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Figure 11 show the Vs case histories compare to the existing triggering curves (e.g., Andrus & Stokoe 2000; Kayen 2004; Zhou & Chen, 2007). As shown in Figure 11, the Vs1 range for liquefied cases is between 125 m/s to 200 m/s, which is mainly due to the fact that these liquefiable deposits are loose to medium dense fine sand in Christchurch area. Note that the Vs datasets appear more constrained than those of CPT, which implies that Vs index is more sensitive to CSR variation in the high velocity zone. And most non-liquefaction cases fall into the “liquefied” zone according to the existing boundary curves. This observation is similar to that by Green et al. (2011). Therefore CPT case histories might be more favorable for liquefaction triggering assessment for relatively stiff (or dense) sandy deposit.

0 100 200 3000.0

0.2

0.4

0.6

Moss & Seed 2004 (PL=20%)

Boulanger & Idriss 2006

Event: 2010 Mw7.1 Liquefied (H.C.) Non-liquefied (M.C.)

Mw=7.5

Cyc

lic S

tress

Rat

io, C

SR

Corrected CPT tip resistance, qc1N


Robertson & Wride 1997

Figure 10. CPT case histories and comparison with existing curves

0 100 200 3000.0

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Kayen 2004(PL=20%)



Zhou & Chen 2007Andrus & Stokoe 2000

Mw=7.5

Cyc

lic S

tress

Rat

io, C

SR

Corrected Shear Wave Velocity, Vs1 (m/s)

Figure 11. Vs case histories and comparison with existing curves


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Table 2. Datasets of Dallington Lower Site

2010 M7.1 2011 M6.3 CPT Sounding

Liq.? Confi.?

Median depth

GWL

Critical qc

Mpa

Critical qc1N

Rf %

FC%

Critical Vs

m/s Vs1 m/s CSR CSR7.5 CSR CSR7.5

DAL-11 Yes(M) 8.5 2.1 12.6 125.2 0.69 1.9 175.0 174.3 0.21 0.19 0.53 0.39 DAL-10 Yes(H) 4.25 2.5 4.8 59.7 0.37 4.1 142.8 160.0 0.17 0.16 0.43 0.32 DAL-8 Yes(H) 4.6 0.9 3.9 52.6 0.51 5.5 131.6 153.1 0.23 0.21 0.57 0.42 DAL-9 Yes(H) 3.5 1.5 2.9 41.1 0.44 5.0 133.3 158.0 0.20 0.18 0.50 0.36 DAL-15 No(M) 4.5 2.4 14.2 174.8 0.58 4.0 134.3 148.8 0.18 0.17 0.46 0.33 DAL-21 No(M) 7.25 2.4 13.8 139.8 0.56 2.6 225.0 225.7 0.21 0.19 0.52 0.38 DAL-25 Yes(H) 5.9 2.2 3.1 35.5 0.68 4.2 156.4 167.2 0.19 0.17 0.48 0.35

CONCLUSIONS First, the CPT and Vs case histories were compiled and compared with the existing boundary curves. The existing evaluation frameworks perform well for both databases. The comparison between CPT and Vs shows that there is generally good agreement between the two, yet there is not enough data in this study to statistically quantify the variance. For the same CSR level, the CPT case histories exhibit more scarcity compared with those of Vs measurement, which indicates the different sensitivity of these two indexes for liquefaction evaluation. Second, the CPT and Vs indexes of a liquefied layer are measured between the 2010 M7.1 and 2011 M6.3 events, and after densification that can occur following the first liquefaction. Therefore it should be noted that the measurements better represent the post-liquefaction resistance of the soil for 2010 event, while they are the pre-liquefaction indexes for the 2011 event. Besides, a series of aftershocks, the largest of which were M5.6 and M6.3, rattled the city on 13 June 2011. These aftershocks again caused liquefaction in many parts of Christchurch, and some further site tests are necessary for the re-liquefied sites after the 2011 event to clarify the possible densification effect. Third, the characteristics of the ground shaking in Christchurch area are different between the two events. Peak ground acceleration is only a single measure of complexity that is better characterized by considering frequency content, duration, and other characteristics of the strong ground shaking. Although the liquefaction triggering is well evaluated by the combination of PGA and MSF in this study, the performance of liquefaction-induced settlement and lateral spreading might be more subjected to the site conditions and earthquake motion characteristics and therefore worth further study.

AKNOWLEDGEMENTS Most of the present work is supported by the National Natural Science Foundation of China (No. 50908207, No. 51127005), the Foundation for the Author of National Excellent Doctoral Dissertation of PR China (No. 201160) and the National Basic Research Program of China (973 Project) (No. 2012CB719801). Prof. Misko Cubrinovski of Canterbury University, New Zealand is appreciated for his kind instructions during the reconnaissance work in Christchurch, and Dr. Russell A. Green of Virginia Tech., USA is also thanked for his encouragement. The publication of geotechnical factual data by EQC is also highly acknowledged.

REFERENCES


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Andrus, R. D. and Stokoe, K.H., II. (2000). “Liquefaction resistance of soils from shear-wave velocity”. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 126(11): 1015-1025.

Boulanger, R.W., Mejia, L. H. and Idriss, I. M. (1997). “Liquefaction at Moss landing during Loma Prieta earthquake”. Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 123(5): 453-67.

Brown, L. J., Weeber, J. H. (1992). Geology of the Christchurch urban area. Institute of Geological & Nuclear Sciences 1:25,000 geological map 1. 1 sheet + 104p. Lower Hutt, New Zealand, Institute of Geological and Nuclear Sciences Limited.

Cubrinovski, M., Green, R., Allen, J., Ashford, S., Bowman, E., Bradley, B., Cox, B., Hutchinson, T., Kavazanjian,E., Orense, R., Pender, M., Quigley M. and Wotherspoon, L. (2010). “Geotechnical reconnaissance of the 2010 Darfield (Canterbury) earthquake”. Bulletin of the New Zealand Society for Earthquake Engineering, 43(4): 243-320.

Cubrinovski, M., Bradley, B., L. Wotherspoon, L. et al. (2011). “Geotechnical aspects of the 22 February 2011 Christchurch earthquake”. Bulletin of the New Zealand Society for Earthquake Engineering, 44 (4): 195-204.

Earthquake Commission, Geotechnical factual data (2011). http://canterbury.eqc.govt.nz/category/ publication-category/report.

Green, R. A., Wood, C., Cox, B., Cubrinovski, M., Wotherspoon, L., Bradley, B., Algie, T., Allen, J., Bradshaw, A. and Rix G. (2011). “Use of DCP and SASW tests to evaluate liquefaction potential: Predictions vs. observations during the recent New Zealand earthquakes”. Seismological Research Letters, 82(6): 927-938.

Idriss, I. M. and Boulanger, R.W. (2006). “Semi-empirical procedures for evaluating liquefaction potential during earthquakes”. Soil Dynamics and Earthquake Engineering 26 115–130

Idriss, I. M. (1999). “An update to the Seed-Idriss simplified procedure for evaluating liquefaction potential”, Proc., TRB Workshop on New Approaches to Liquefaction, January, Publication No. FHWA-RD-99-165, Federal Highway Administration.

Kayen, R., Seed, R. B., Moss, R. E., Cetin, O., Tanaka, Y., and Tokimatsu, K. (2004). “Global shear wave velocity database for probabilistic assessment of the initiation of seismic-soil liquefaction”. Proc., 11th Int. Conf. On Soil Dynamics and Earthquake Engrg., 2, Berkeley, CA, pp.506-512.

Moss, R. (2003). “CPT-based probabilistic assessment of seismic soil liquefaction initiation”, Ph.D. thesis, University of California, Berkeley, CA.

Natural Hazards Research Platform (NHRP) (2011). Why the 2011 Christchurch Earthquake is Considered an Aftershock. http://www.naturalhazards.org.nz/.

Orense, R. P., Kiyota, T., Yamada, S., Cubrinovski, M., Hosono,Y., Okamura, M. and Yasuda S. (2011). “Comparison of liquefaction Features observed during the 2010 and 2011 Canterbury earthquakes”. Seismological Research Letters, 82(6): 905-918.

Robertson, P. K., Wride, C. E. (1998). “Evaluating cyclic liquefaction potential using the cone penetration test”. Canadian Geotechnical Journal, 35(3): 442-59.

Seed, H. B. and Idriss, I. M. (1971). “Simplified procedure for evaluating soil liquefaction potential”. Journal of the Soil Mechanics and Foundations Division, ASCE, 97(SM9): 1249-1273.

Segou, M. and Kalkan, E. (2011). “Ground motion attenuation during M 7.1 Darfield and M 6.2 Christchurch, New Zealand, earthquakes and performance of global predictive models”. Seismological Research Letters, 82(6): 866-874.

Smyrou, E., Tasiopoulou, P., Bal Ï. E. and Gazetas, G. (2011). “Ground motions versus geotechnical and structural damage in the February 2011 Christchurch earthquake”. Seismological Research Letters, 82(6): 882-892.

Youd, T. L., et al. (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, ASCE, 127(10): 817-833.

Zhou, Y. G. and Chen, Y. M. (2007). “Laboratory investigation on assessing liquefaction resistance of sandy soils by shear wave velocity”, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 133(8): 959-972.

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LIQUEFACTION PERFORMANCE CASE HISTORIES …or.nsfc.gov.cn/bitstream/00001903-5/148326/1/1000003698987.pdf · II International Conference on Performance Based Design in Earthquake