ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
Transcript of ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 1/25
1
ESTIMATION OF EARTHQUAKE
INDUCED SETTLEMENTS AND
LIQUEFACTION POTENTIAL INSANDY SOIL
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 2/25
2
INTRODUCTION
Practical relevance of the topic
Procedure for estimation of earthquake
induced settlement in sandy soil (Lee,2007)
Procedure for estimation of liquefaction
potential (Idriss and Boulanger ,2004)
Summary and conclusions
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 3/25
3
ESTIMATION OF SETTLEMENT (Lee,2007
)
The total settlement, S for a sandy soil
(1)
Where,
Hi = thickness for layer i
εvi = volumetric strain for layer i
n = number of soil layers.
∑=
=n
i
H S vii
1
ε
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 4/25
4
Volumetric strain (Lee,2007 )
εv = 10(N)-0.6
(2)
for
Where,
εv = volumetric strain;
N = SPT value
CSR = Cyclic stress ratio
01.0)( >
N
CSR
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 5/25
5
N
Fig.1.Relationship between volumetric strain and
N
(source: Lee, 2007)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 6/25
6
Determination of Cyclic stress ratio
MSF g
aCSR d
v
vr /)())(( max
'65.0
σ
σ =
Where,
CSR = cyclic stress ratio
σv = total overburden pressure at the depth considered;
σv’ = effective overburden pressure at the same depth;
amax
= maximum horizontal acceleration at the ground surface;
g = acceleration due to earth’s gravity;
r d
= stress reduction factor; and
MSF = magnitude scaling factor.
(3)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 7/25
7
Determination of Magnitude scaling factor
MSF = 2.5 - 0.2M (4)
(source: Lee, 2007)Fig.2 Relationship between magnitude scaling factor and M
Where,
M = magnitude of earthquake.
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 8/25
8
Determination of Stress reduction factor (r d)
Loge (r d) = α (z) + β(z) M (5a)
α (z) = -1.102 – 1.126sin{(z/11.73) + 5.133} (5b)
β (z) = 0.106 + 0.118 sin {(z/11.28) + 5.142} (5c)
Where,
z = depth in meters
M = earthquake magnitude
For z > 34m,
r d = 0.12 exp(0.22M) (5)
For z <= 34m,
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 9/25
9
COMPARISON OF PREDICTION BY THE LEE (2007)
METHOD WITH FIELD OBSERVATIONS
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 10/25
10
Tokachi-Oki earthquake, Japan (1968)
Fig.3 Computed distribution of CSR
with depth (source:Lee, 2007 )
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 11/25
Fig.4 Comparison of computed distributions of
volumetric strain with depth (source: Lee,2007)
11
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 12/25
12
Fig.5 Computed distributions of settlement with depth
(source: Lee, 2007)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 13/25
Fig.6 Comparison of computed and measured Settlements
(source: Lee, 2007)
13
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 14/25
14
Loma Prieta earthquake, San Francisco (1989)
Fig.7 Computed distribution of CSR with depth
(source: Lee, 2007)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 15/25
15
Fig.8 Comparison of computed distributions of
volumetric strain with depth (source: Lee, 2007)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 16/25
Fig.9 Comparison of computed distributions of
settlement with depth (source: Lee, 2007)
16
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 17/25
17
Fig.10 Comparison of computed and measured settlements.
(source: Lee, 2007)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 18/25
18
ESTIMATION OF LIQUEFACTION POTENTIAL
(Idriss and Boulanger ,2004)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 19/25
CPT BASED SEMI EMPIRICAL METHOD
CSR = exp { (qc /540) + (qc /67)2 – (qc /80)3 + (qc /114)4 -3 } (6)
Where,
qc = CPT tip resistance.
19
(Idriss and Boulanger ,2004)
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 20/25
CPT Tip Resistance qc
Fig.11 CPT-based case histories and recommended relation
for clean sands. (source: Idriss and Boulanger, 2007)
20
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 21/25
• Determine the soil characteristics using CPT.
• Determine the CSR value
• Corresponding to the known value of CSR and CPT tipresistance, mark a point in fig.11
• If the point lies below the line of separation
recommended by Idriss and Boulanger (2004), it indicates
that liquefaction is not likely to occur.
Procedure
21
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 22/25
SUMMARY
Effective and simple methods for
estimation of earthquake induced settlement (Lee,2007)
estimation of liquefaction potential (Idriss and Boulanger ,2004)
22
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 23/25
23
CONCLUSIONS
The procedure for estimation of earthquake induced
settlement by Lee,(2007) method is quite simple
Good agreement is obtained between the predicted results
by the approach proposed by Lee (2007) and the measured
results at two sites
8/14/2019 ESTIMATION OF EARTHQUAKE INDUCED SETTLEMENTS AND LIQUEFACTION POTENTIAL IN SANDY SOIL
http://slidepdf.com/reader/full/estimation-of-earthquake-induced-settlements-and-liquefaction-potential-in 24/25
CPT provides a continuous record of the penetration
resistance and is less vulnerable to operator error than is
the SPT test. This totally eliminates any missing out of
liquefiable soil layer.
The Idriss and Boulanger (2004) boundary line can be
conveniently used to separate liquefiable and non liquefiable
soils
Contd…
24