Speaker: Jin Hung Hwang Prof., Civil Engineering ...
Transcript of Speaker: Jin Hung Hwang Prof., Civil Engineering ...
On the Simplified Methods Liquefaction Potential of
: Twenty Years Development of
Speaker: Jin
Prof., Civil Engineering Department, National Central University, Taiwan
Geotechnical Division Head, NCREE
Methods for Assessing Liquefaction Potential of Soils
Development of HBF Method
Jin Hung Hwang
Prof., Civil Engineering Department, National Central University, Taiwan
Geotechnical Division Head, NCREE
Flow Chart to Solve Liquefaction Problems
Start
Liquefaction
triggering
1
2
3
4
5
No
Yes
Simplified
method
5
6
Flow instability
Ground improvement
+
Deep foundation
End
Yes
Yes
No
Flow Chart to Solve Liquefaction Problems
Assessing consequences
1. Liquefaction potential index (LPI)
2. Post-liquefaction settlement
3. Reduction coefficients for kh and pu
4.Flow pressure and displacement
5. Building settlement due to liquefaction5. Building settlement due to liquefaction
6. floating check
Acceptable?
Yes
No
Outline
�Introduction to the simplified methods commonly used in the world
�Framework of NCREE-HBF method and its main �Framework of NCREE-HBF method and its main features
�Comparison Studies of the simplified methods
�Conclusions and suggestion
Outline
Introduction to the simplified methods commonly used
HBF method and its main HBF method and its main
Comparison Studies of the simplified methods
Conclusions and suggestion
Introduction
�The pioneer works on the simplified stress based method�Seed & Idriss (1971); Seed & Idriss (1979); Seed et al.(1985)
�Other followers in USA:Youd et al.(2001); Cetin et al.(2004); Idriss and Boulanger (2004); Boulanger and Idriss(2014)
� The similar works in Japan� The similar works in Japan� Iwasaki et al.(1982); JRA(1990,1996);
AIJ(2001)
�A new simplified method called HBF was developed in Taiwan�Basing on Chi-Chi earthquake cases
�A cyclic resistance ratio curve of HyperBolic
�Verification by local and worldwide liquefied and non
Introduction
The pioneer works on the simplified stress based method(1979); Seed et al.(1985)
Other followers in USA:Youd et al.(2001); Cetin et al.(2004); Idriss and Boulanger (2004); Boulanger and Idriss(2014)
Iwasaki et al.(1982); JRA(1990,1996); Tokimatsu and Yoshimi(1983);
A new simplified method called HBF was developed in Taiwan
HyperBolic Function(HBF) is used
Verification by local and worldwide liquefied and non-liquefied data
The Framework of the Simplified Assessing Soil Liquefaction Potential
CRRKKKCRR MFC ⋅⋅⋅== =
σασ
Black Box
MSFrA
CSRd
v
v
MFC
165.0 max ⋅⋅⋅
′⋅
== =
σσ
ασ
MCRRThe key relation is
The Framework of the Simplified Method for Assessing Soil Liquefaction Potential
5.7=Performance Check
MSF
15.7=
Verification by liquefied and
non-liquefied earthquake cases
sandclean for )(N vs. 6015.7=M
Parameters in the black box used in liquection triggering analysis
Description Parameter
CRRCyclic resistance curve
SPT borehole correction factors
Overburden stress
Diving energy
Rod length
Borehole size
Sampler
C
C
C
C
CSampler C
Fines correction FC
CRR stress adjustment
CRR initial stress adjustment
Magnitude scaling factor
Shear stress reduction factor
K
K
MSF
r
∗ :Neglectable
Parameters in the black box used in liquection triggering analysis
Parameter Notes
5.7CRR sandclean for )( vs CS6015.7 NCRR
NC
EC
RC
BC
C
NCCCCCN sBREN ⋅=601)(
∗∗∗
SC
(%) vs)(N 601 FC∆(%)FC
601601601 )(N)N()(N ∆+=CS
σK
αK
MSF
dr
5.7CRRKKCRR ⋅⋅= ασ
Number of cycles
Visco-elastic seismic response
∗∗
∗
Neglectable
Seed et al. Method �The pioneer and original
works (1971, 1979, 1983, 1985)
�All the parameters need to refer figures
Peak ground acceleration
maxa
to refer figures
�Innovative and intrinsic framework to solve problems of soil mechanics
�It is still good enough now since it was established 48 years ago
Earthquake induced cyclic
shear stress ratio
CSR ×= 65.0
Peak ground accelerationEarthquake
magnitudeSPT Eff. overburden Fines content
Ground propertiesEarthquake
maxwM 60N )kPa( vσ ′ (%) FC
( ) ( ) 60601 NCN vN ×σ′=規模修正因子
refer figureNC
dr
11.1)5.7
( −= wMMSF
15.7 ( NvsCRRrefer figure
5.7CRR
Cyclic resistance ratio
MSFCRRCRR ×=5.7
CSR
CRRFS =
Earthquake induced cyclic
shear stress ratio
d
v
v rg
a ×′σ
σmax
refer figure15.7
NCEER Method(2001)
�Based on Seed method (1985) with complicated equations to fit original CRR curves, stress reduction factor and fines correction factor correction factor
�This method is nearly the same as Seed et al’s method.
�The proposed method has been discussed by many experts in a NCEER workshop(1997)
�A representative of US method
Earthquake induced cyclic
Peak ground
acceleration
Moment
magnitudeSPT
Ground propertiesEarthquake
maxawM 60N
( ) 60'601 NP
Nv
a ×=σ
Magnitude
scaling factor
56.2)5.7
( −= wMMSF
32 +++= gxexcxaCRR
601601)()( NN
csβα +=
[0.5
190(76.1
0
=−=
=
ααα
EXP
[2.1
1000/(99.0
0.15.1
=+=
=
βββ
FC
%35
%355
%5
><
FC
FC
FC
≦
≦
%35
%355
%5
><
FC
FC
FC
≦
≦
Fines content
(%) FC
Eff. overburden
)kPa( vσ ′
Safety factor
CSR
CRRFS =
Earthquake induced cyclic
shear stress ratio
d
v
v rg
aCSR ×
′×=
σσmax65.0
Cyclic resistance ratio
MSFCRRCRR ×= 5.7
06714.3,05673.1,04285.3
,04136.6,03578.9,03721.4
,01248.1,02844.4,)(
1
601
4325.7
−=−−=−−=−=−=−−=
−−=−==++++
+++=
EhegEf
EeEdEc
EbEaNx
hxfxdxbx
gxexcxaCRR
CS
)001210.0006205.005729.04177.0000.1(
)001753.004052.04113.0000.1(25.15.0
5.15.0
zzzz
zzzr
d +−+−++−=
JRA Method (1996)
�Peak shear stress ratio
�Neglecting influence of earthquake magnitude
�Resistance depending on earthquake type
Design seismic coefficient
Peak shear stress ratio
earthquake type
�Conservative for soils with high N value
�Non-conservative for soils with high fines content and little plasticity
Sandy soils need to be assessed to obtain their liquefaction potential
(1)water table less than 10m below G.L. and saturated sandy soils within 20m below G.L.
(2)fines content FC≦35% 或FC>35% with plasticity index Ip<15%.
(3)mean grain D50≦10mm with 10% grain size D10≦1mm.
Design seismic coefficient
SPT Effective overburdenFines content ,
Peak shear stress ratio
zr
krL
d
v
vhcd
015.01−=′
××=σσ Earthquake type I: 0.1=wc
)4.0...(
)4.01.0...(
)10...(
0.2
67.03.3
0.1
L
L
Lw
R
R
.R
Rc
<≤<
≤
+=
Lw RcR ⋅=Cyclic resistance ratio
(%) FC
(mm) 50D (mm) 10D N )kPa( vσ ′
hck
Earthquake type II:
Safety factor
L
RFS =
)4.0...(0.2 LR<
( )
≤<
−××+= − )N...(14
14)...(N
14106.17.1/0882.0
7.1/0882.0
a
a
5.46
aa
a
LNN
NR
Sandy soils:
211 cNcNa +=
70σ'
170
v
1 +×= N
N
≤<≤
<≤
−+=
)...(60%
60%)...(10%
10%)...(0
1)20(
50)40(
1
1
FC
FC
FC
FC
FCc
≤<≤
−=
)...(10%
10%)...(0
18)10(
02
FC
FC
FCc
Gravelly soils:
( )[ ]15010 2log361.01 NDNa ××−=
AIJ Method (2002)
�Based on the method proposed by Tokimatsu and Yoshimi(1983)
�Equivalent shear stress ratio
�The function of cyclic resistance
1
2
�The function of cyclic resistance curve is also simple
�The framework is similar to that of USA
�Fines correction is non-conservative
Peak ground accelerationMoment
MagnitudeSPT Eff. overburden Fines content
Ground propertiesEarthquake
<≤<≤<
≤<≤
−×+−×+
−×=
%50
%20
%10
1%5
5%
11
)20(1.08
)10(2.06
)5(1.2
0
∆
FC
FC
FC
FC
FC
FC
FC
FC
N f
A72N (%) FC)kPa( 0vσ ′
wM
( )72'721
98NN
v
×=σ
Sandy soils susceptible to liquefaction
1.Alluvial saturated soil layers within 20m below G.L. and with fines content <35%
2.Soils with fines content>35% and with clay content<15% or with plasticity index Ip<
Pa
tf/m2
Safety factor
fa NNN ∆+= 721)(
Earthquake induced
average shear stress ratio
zr
rg
AMCSR
d
d
v
vw
015.01
)1(1.00
0
−=′
−=σσ
Cyclic Resistance ratio
CRR
CSR
CRRFL =
Cycli
c r
esis
tance
rati
o
CR
R
Adjusted N value (Na)
3020100
0.1
0
0.2
0.3
0.4
0.5
0.6Shear strain γ=5%
+=
80
16
100
162565.0
aNN
CRR
NCREE- HBF
�Based on the liquefied and non-liquefied cases of 1999 Chiearthquake
�Use of HyperBolic Fuction (HBF) to fit cyclic resistance ratio curve�Use of HyperBolic Fuction (HBF) to fit cyclic resistance ratio curve
�The equations used are as elegant and simple as possible
�Soils with Ip>7 are regarded as clayliquefaction
Method (2019)
liquefied cases of 1999 Chi-Chi
(HBF) to fit cyclic resistance ratio curve(HBF) to fit cyclic resistance ratio curve
The equations used are as elegant and simple as possible
>7 are regarded as clay-like soils and unsusceptible to
Framework of HBF Methodand Its Main Features
Feature 1: All the formula used to
calculate cyclic resistance ratio (CRR),
stress reduction factor (rd), correctionstress reduction factor (rd), correction
factor of fines content (Ks),
magnitude scaling factor (MSF), and
overburden stress correction factor
(CN) are as simple and elegant as
possible so that engineers can prevent
calculation errors or coding mistakes
that commonly encountered in
practices.
Method
maxawM 60N )kPa( vσ ′
8.1)
5.7(
−= wMMSF
( ) 60'601 NP
Nv
a ×=σ
07.01
10
0.1
10
×+=
>=
≤
FCk
FCIf
k
FCIf
s
s
(%) FC
d
v
v rg
aCSR ×
′×=
σσmax65.0
mzm
mz
z
zrd
2010
10
03.02.1
01.00.1
≤<≤
−−
=
MSFCRRCRR ×= 5.7
CSR
CRRFS =
39/)(1
)(0035.008.0
)()(
601
6015.7
601601
cs
cs
scs
N
NCRR
NkN
−×+=
×=
The Main Features of HBF Method
Feature 2: The method fits the CRR (Mw=7.5) curve of clean sand by using a hyperbolic function
The Main Features of HBF Method
The Main Features of HBF Method
Feature 3: The HBF method believesindex PI>7 are clay-like materialsexhibit cyclic softening behavior underexhibit cyclic softening behavior underin consistent with the suggestion byas the definition of clay soil inCasagrande (1948), and the studycohesive soils (Hwang et al., 2000).
The Main Features of HBF Method
believes the cohesive soils with plasticitymaterials which will not liquefy and only
under seismic shaking. This criteria isunder seismic shaking. This criteria isBoulanger and Idriss (2006) as wellthe plasticity chart proposed byon the cyclic resistance of Taipei
The Main Features of HBF Method
Feature 4: A lot of liquefied cases ofplastic ML soils in central Taiwanobserved during Chi-Chi earthquake (et al., 2004) and then resulted in severalexperimental researches on these non-plasticexperimental researches on these non-plasticsoils (Huang et al., 2007; Chen et al, 2014The conclusion is the correction ofcontent on CRR is suggested to be aconservative, especially for non-plasticsoils.
The Main Features of HBF Method
of non-were
(Uengseveralplastic
0.3
0.4
0.5
CR
R
NCEER
JRA
AIJ
HBF
(N1)60cs=15
plastic2014).Fines
a littleplastic ML
0.0
0.1
0.2
0 20 40 60 80 100
CR
R
細料含量 (%)
A Comparison of Cyclic Strength Curve
Method Cyclic strength curve (CRR
NCEER(2001) CRR7.5 = 134 − �N1 60cs + �N135
CRR7.5 = exp ��N1 60 �1+0.004FCCetin et al.(2004)
HBF(2012)
Boulanger and
Idriss (2014)
CRR7.5 = 0.08 + 0.0035�N1 1 − �N1 60cs
CRR7.5 = exp ��N1 60cs14.1 + ��N
CRR7.5 = exp ��N1 60 �1+0.004FC
A Comparison of Cyclic Strength Curve
Cyclic strength curve (CRR7.5)
�N1 60cs135 + 50�10�N1 60cs + 45 2 − 1200
FC −29.53 ln �Mw −3.7 ln σ vP a %+0.05FC +16.85+2.7Φ−1�0.15,0,1 13.32 (
� 60cs cs /39
��N1 60cs126 (2 − ��N1 60cs23.6 (3 + ��N1 60cs25.4 (4 − 2.8*
FC −29.53 ln �Mw −3.7 ln σ vP a %+0.05FC +16.85+2.7Φ−1�0.15,0,1 13.32 (
A Comparison of Stress Reduction Factor
Method Stress
NCEER(2001) rd = 1.0 − 0.41131.0 − 0.4177z0.
z < 20m, rd = 11Cetin et al.(2004)
HBF(2012)
Boulanger and
Idriss (2014)
z < 20m, rd = 11
rd = 1 − 0.01rd = 1.2 − 0
rd =α�z = −1.012β�z = 0.106
A Comparison of Stress Reduction Factor
Stress reduction factor (rd)
4113z0.5 + 0.04052z + 0.001753z1.5.5 + 0.5729z − 0.006205z1.5 + 0.00121z2
1 + −23.013−2.949amax +0.999Mw +0.0525VS12m∗16.258+0.201e0.341 �−z +0.0785 V s12m∗ +7.586
1 + −23.013−2.949a +0.999M +0.0525V∗
34
1 + −23.013−2.949amax +0.999Mw +0.0525VS12m∗16.258+0.201e0.341 �−z +0.0785 V s12m∗ +7.586
1 + −23.013−2.949amax +0.999Mw +0.0525VS12m∗16.258+0.201e0.341 �0.0785 V s12m∗ +7.586
01z from z�m ≤ 10 0.03z from 10 < z�m ≤ 10
= exp9α�z + β�z M:012 − 1.126sin z11.73 + 5.133%
106 + 0.118sin z11.28 + 5.142%
A Comparison of Fines Content Correction
Method Fines content correction (C
NCEER(2001)α = 0; β = 0 α = exp91.76 − �190α = 5; β = 1.2
CFINESCetin et al.(2004)
HBF(2012)
Boulanger and
Idriss (2014)
Ks = 1 Ks = 1
CFINES
�N1∆�N1 60 =
A Comparison of Fines Content Correction
Fines content correction (CN)
�N1 60cs = α + β�N1 60 for FC ≤ 5 190/FC2 :; β = 0.99 + FC 1.5
1000 for 5 < FC ≤ 35 for FC > 35
= 1 + 0.004FC + 0.05 FC�N %
34
�N1 60cs = Ks�N1 60 for FC ≤ 10+ 0.07√FC − 10 for FC > 10
= 1 + 0.004FC + 0.05 FC�N1 60 %
Lim:5%≤FC≤35%
� 1 60cs = �N1 60 + ∆�N1 60
= exp 1.63 + 9.7FC +0.01−C 15.7FC +0.01D2%
COMPARISON STUDIES OF THE HBF METHOD�A total of 669 sets of SPT-based cases were
�302 sets of Chi-Chi earthquake data collected by Hwang and Yang (2001)
�367 sets of data collected by Youd et al. (1997
� Summary of comparison using success rate of prediction
Success rate Seed (1985) NCEER (2001)
FC≤10 96% 97%
Liquefied
FC≤10 96%(143/149) 97%(145/149)
10<FC≤30 88%(136/155) 92%(142/155)
FC>30 91%(63/69) 97%(67/69)
Non-
liquefied
FC≤10 59%(62/105) 57%(60/105)
10<FC≤30 88%(130/147) 86%(126/147)
FC>30 91%(40/44) 82%(36/44)
Liquefied 92%(342/373) 95%(354/373)
Non-liquefied 78%(232/296) 75%(222/296)
Total 86%(574/669) 86%(576/669)
COMPARISON STUDIES OF THE HBF METHODbased cases were collected
data collected by Hwang and Yang (2001)
et al. (1997)
Summary of comparison using success rate of prediction
AIJ (1983) JRA (1996) JRA (1990) HBF (2005)
99% 99% 87% 95%99%(147/149) 99%(147/149) 87%(130/149) 95%(142/149)
90%(140/155) 97%(150/155) 81%(126/155) 98%(152/155
94%(65/69) 97%(67/69) 81%(56/69) 99%(68/69
50%(53/105) 43%(45/105) 61%(64/105) 64%(67/105
77%(113/147) 67%(99/147) 79%(116/147) 80%(117/147
75%(33/44) 75%(33/44) 64%(28/44) 75%(33/44
94%(352/373) 98%(364/373) 84%(312/373) 97%(362/373
67%(199/296) 60%(177/296) 70%(208/296) 73%(217/296
82%(551/669) 81%(541/669) 78%(520/669) 87%(579/669
A comparison of Microof Soil Liquefaction Potential
�Using liquefaction potential index(PL) by Iwasaki et al. (1978)
� The area of different liquefaction potentials in Taipei basin by different methodsbasin by different methods
Method
Liquefaction potential
Low Middle
Area
HBF (2005) 101.3/39% 95.0/36%
NCEER (2001) 111.7/43% 98.0/37%
JRA (1996) 76.3/29% 104.6/40%
Micro-zonation MapSoil Liquefaction Potential in Taipei basin
Liquefaction potential Total
Middle High
Area(km2)/Percentage
/36% 65.6/25% 261.9/100%
/37% 52.1/20% 261.9/100%
/40% 80.9/31% 261.9/100%
A comparison of Microof Soil Liquefaction Potential in Taipei basin
HBF(2005) NCEER(2001)
A comparison of Micro-zonation Mapof Soil Liquefaction Potential in Taipei basin
NCEER(2001) JRA(1996)
Conclusions and
�All the methods are acceptable in engineering practice.
�Each method is an integrated system. You can not replace one of the elements in A method with that in B method.
�The prediction accuracy of new methods are not necessarily better than the old methods.
�The prediction accuracy of more complicated methods are not necessarily better than simple methods
�The main features and the merits of HBF method are
�The HBF method has more simple and elegant formula
�The performance of HBF method is as good as NCEER method
�It is suggested that the HBF method can be an acceptable alternative for assessing liquefaction potential in practice
Conclusions and suggestions
All the methods are acceptable in engineering practice.
Each method is an integrated system. You can not replace one of the elements in A method with that in B method.
The prediction accuracy of new methods are not necessarily better
The prediction accuracy of more complicated methods are not simple methods.
main features and the merits of HBF method are illustrated
simple and elegant formula
performance of HBF method is as good as NCEER method
method can be an acceptable alternative for assessing liquefaction potential in practice beside USA and Japan
Thank you very muchThank you very muchfor
your attentions
Thank you very muchThank you very muchfor
your attentions