ct5_class_a
TRANSCRIPT
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Ear t hquake Induced Damage
Mi t igat ion f rom Soi l Liquefac t ion
CLASS A PREDICTION FOR LIQUEFACTION REMEDIATION
INITIATIVE CENTRIFUGE TEST 5 (LRICT5)
By:Ahmad Jafari
Supervisor: Dr. Radu Popescu
Memorial University of NewfoundlandNovember, 2004
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Introduction
In this report Class A prediction of the 5th LRI (Liquefaction Remediation Initiative)
centrifuge test (LRICT5) is presented and discussed. The recalibrated soil parameters,
used in class A prediction of the LRICT4 centrifuge experiment, have been used to
predict the behavior of soil due to seismic loads.
LRICT5 geometry and input motion
General layout and input motion used for class A prediction of LRICT5 are shown in
Figures1 and 2. The slope has an inclined silt layer with a slope of 1:5.7 and the
mitigation strategy includes three drainage dykes as shown in Figure 1. The input
acceleration time history used in this test is A2475 with a magnification factor of 2, i.e.
2A2475 as shown in Figure 2. The FE model for this prediction is shown in Figure 3.
The model consists of 588 nodes and 542 elements.
Figure 1. Geometry and instrumentation layout of LRICT5 given by C-CORE
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Figure 2. Input acceleration time history used for LRICT5
Figure 3. FE mesh used in class A prediction of LRICT5
Soil properties
Regarding loose sand and drainage dyke the same material properties, previously used in
class A prediction of LRICT4, have been used in class A prediction of LRICT5. It is
mentioned that there has been no relevant information on the silt and only general test
results have been made available for the gravel; therefore, the required constitutive
parameters have been estimated based on engineering judgment and previous experience
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with similar materials. Table 1 includes the assumed set of soil properties of silt used in
this class A prediction. Hydraulic conductivity of silt is considered to be 1/100 of the
hydraulic conductivity of loose sand, as used by UBC in their class A predictions for
COSTA-B. The material properties of sand and drainage dyke were reported in class A
prediction of LRICT4.
Table 1. Assumed set of silt constitutive parameters
Results of Class A prediction of LRICT5
Results of class A prediction of the 5th
centrifuge test are discussed hereafter. Figure 4
shows vertical displacement contours at the end of analysis (t = 42.56s). The predicted
settlement at upslope free field is larger than 0.4m. The predicted maximum shear strain
contours are shown in Figure 5 along with the deformed shape of the model. The
predicted excess pore water pressure contours at different instants are shown in Figures 6
to 10. Due to the presence of dykes considerable reduction in excess pore pressure is
predicted in regions close to the dykes; however, in the free field, U/S of the drainage
dykes, significant pore water pressure generation is predicted. The large values predicted
near the lateral boundaries are due to boundary effects. As it can be seen in Figures 9 and
10, after the end of the strong shaking at about t=20s, the maximum pore water pressure
Constitutive parameters Symbol
Assumed
Values Type
Mass density (kg/m3)
Porosity
Hydraulic conductivity (permeability) (cm/s)
swn
k
2670
0.448
0.000084
State
Parameters
Low-strain shear modulus (Mpa)
Reference effective mean normal stress
Powe exponent
Poisson ratio
0G 0p
n
2
100
0.8
0.4
Elastic
Parameters
Friction angle at failure
Coefficient of lateral earth pressure at rest
Soil cohesion
Maximum deviatoric strain
(C= compression, E=extension)
0k
cmaxdev
22o
1
0
0.10 (C),
0.10 (E)
Yield
Parameters
Dilation angle (phase transformation angle)
Dilation parameter
PPX
17o
0.04
Dilation
Parameters
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values below the U/S region move upwards towards the silt layer. In the D/S region pore
pressures are predicted to dissipate after the end of shaking (t >20 s). Figures 11 to 33
show the predicted responses at different transducers. It is mentioned that LVDT2
measures displacement time history in a direction parallel to the silt layer. Up to about
0.25 m heave is predicted at LVDT4 location (Figure 14). As discussed earlier in the free
field, U/S of the drainage dykes, e.g. EPP5, remarkably large excess pore water pressure
generation is predicted after the end of shaking, and it results in occurring of liquefaction
in that area as shown in Figure 19. The numerical model predicts significant dilation (i.e.
large negative excess pore water pressures) between t= 12 s and t= 17s, especially at very
shallow locations (EPP4, EPP5, EPP8 and EPP9).
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Figure 4. Predicted vertical displacement contours at t=42.56 s
Figure 5. Predicted maximum shear strain contours at t=42.56 s
(Deformed shape magnification factor= 1)
Figure 6. Predicted excess pore water pressure ratio contours at t=12 s
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Figure 7. Predicted excess pore water pressure ratio contours at t=16 s
Figure 8. Predicted excess pore water pressure ratio contours at t=20 s
Figure 9. Predicted excess pore water pressure ratio contours at t=30 s
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Figure 10. Predicted excess pore water pressure ratio contours at t=42.56 s
0 1 0 2 0 3 0 4 0 5 0- 0 . 3 5
- 0 . 3
- 0 . 2 5
- 0 . 2
- 0 . 1 5
- 0 . 1
- 0 . 0 5
0
0 . 0 5L V D T 1 t im e h i s t o r y
T i m e ( s )
Displacement(m)
Figure 11. Predicted vertical displacement time history at LVDT1
0 1 0 2 0 3 0 4 0 5 0- 0 . 2
0
0 . 2
0 . 4
0 . 6
0 . 8
1
1 . 2L V D T 2 t im e h i s t o r y
T im e ( s )
Displacement(m)
Figure 12. Predicted total displacement time history at LVDT2 along the silt layer
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0 1 0 2 0 3 0 4 0 5 0- 0 . 4
- 0 . 3 5
- 0 . 3
- 0 . 2 5
- 0 . 2
- 0 . 1 5
- 0 . 1
- 0 . 0 5
0
0 . 0 5L V D T 3 t im e h i s to r y
T im e ( s )
Displacement(m)
Figure 13. Predicted vertical displacement time history at LVDT3
0 1 0 2 0 3 0 4 0 5 0- 0 . 0 5
0
0 . 0 5
0 . 1
0 . 1 5
0 . 2
0 . 2 5
0 . 3L V D T 4 t i m e h i s t o r y
T i m e ( s )
Displacement(m)
Figure 14. Predicted vertical displacement time history at LVDT4
0 1 0 2 0 3 0 4 0 5 0- 0 . 7
- 0 . 6
- 0 . 5
- 0 . 4
- 0 . 3
- 0 . 2
- 0 . 1
0
0 . 1
0 . 2P o r e P r e s s u r e R a t i o t im e h i s t o r y a t E P P 1
T i m e ( s )
RU
Figure 15. Predicted excess pore water pressure ratio time history at EPP1
IEVS=50 KPa
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0 1 0 2 0 3 0 4 0 5 0- 0 . 1
0
0 . 1
0 . 2
0 . 3
0 . 4
0 . 5
0 . 6
0 . 7P o r e P r e s s u r e R a t i o t im e h i s t o r y a t E P P 2
T i m e ( s )
RU
Figure 16. Predicted excess pore water pressure ratio time history at EPP2
0 1 0 2 0 3 0 4 0 5 0- 0 . 2
- 0 . 1
0
0 . 1
0 . 2
0 . 3
0 . 4
0 . 5
0 . 6
0 . 7
P o r e P r e s s u r e R a t io t im e h i s to r y a t E P P 3
T i m e ( s )
RU
Figure 17. Predicted excess pore water pressure ratio time history at EPP3
0 1 0 2 0 3 0 4 0 5 0- 1 0
- 8
- 6
- 4
- 2
0
2P o r e P r e s s u r e R a t i o t im e h i s t o r y a t E P P 4
T i m e ( s )
RU
Figure 18. Predicted excess pore water pressure ratio time history at EPP4
IEVS=121 KPa
IEVS=12 KPa
IEVS=88.5 KPa
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0 1 0 2 0 3 0 4 0 5 0- 1 . 5
- 1
- 0 . 5
0
0 . 5
1P o r e P r e s s u r e R a t i o t im e h i s t o r y a t E P P 5
T i m e ( s )
RU
Figure 19. Predicted excess pore water pressure ratio time history at EPP5
0 1 0 2 0 3 0 4 0 5 0- 0 . 5
- 0 . 4
- 0 . 3
- 0 . 2
- 0 . 1
0
0 . 1
0 . 2
0 . 3
0 . 4P o r e P r e s s u r e R a t io t i m e h i s t o r y a t E P P 6
T i m e ( s )
RU
Figure 20. Predicted excess pore water pressure ratio time history at EPP6
0 1 0 2 0 3 0 4 0 5 0- 1
- 0 . 8
- 0 . 6
- 0 . 4
- 0 . 2
0
0 . 2
0 . 4P o r e P r e s s u r e R a t i o t i m e h i s t o r y a t E P P 7
T i m e ( s )
RU
Figure 21. Predicted excess pore water pressure ratio time history at EPP7
IEVS=31 KPa
IEVS=47 KPa
IEVS=44 KPa
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0 1 0 2 0 3 0 4 0 5 0- 4
- 3 . 5
- 3
- 2 . 5
- 2
- 1 . 5
- 1
- 0 . 5
0
0 . 5P o r e P r e s s u r e R a t i o t im e h i s t o r y a t E P P 8
T i m e ( s )
RU
Figure 22. Predicted excess pore water pressure ratio time history at EPP8
0 1 0 2 0 3 0 4 0 5 0- 2
- 1 . 5
- 1
- 0 . 5
0
0 . 5
1P o r e P r e s s u r e R a t io t i m e h i s t o r y a t E P P 9
T i m e ( s )
RU
Figure 23. Predicted excess pore water pressure ratio time history at EPP9
0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 1
T i m e ( s )
Accele
ration(m/
s2)
Figure 24. Predicted acceleration time history at ACC01
IEVS=15 KPa
IEVS=15 KPa
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0 1 0 2 0 3 0 4 0 5 0- 3
- 2
- 1
0
1
2
3A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 2
T i m e ( s )
Acceleration(m/
s2)
Figure 25. Predicted acceleration time history at ACC02
0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 3
T i m e ( s )
Acceleration(m/
s2)
Figure 26. Predicted acceleration time history at ACC03
0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 4
T i m e ( s )
Acceleration(m/
s2)
Figure 27. Predicted acceleration time history at ACC04
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0 1 0 2 0 3 0 4 0 5 0- 3
- 2
- 1
0
1
2
3
4
5A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 5
T i m e ( s )
Acceleration(m/
s2)
Figure 28. Predicted acceleration time history at ACC05
0 1 0 2 0 3 0 4 0 5 0- 5
0
5
A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 6
T i m e ( s )
Acceleration(m/
s2)
Figure 29. Predicted acceleration time history at ACC06
0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4A c c e l e r a t io n t i m e h i s t o r y a t A C C 0 7
T i m e ( s )
Acce
leration(m/
s2)
Figure 30. Predicted acceleration time history at ACC07
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0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4
5A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 8
T i m e ( s )
Acceleration(m/
s2)
Figure 31. Predicted acceleration time history at ACC08
0 1 0 2 0 3 0 4 0 5 0- 5
0
5A c c e l e r a t i o n t i m e h i s t o r y a t A C C 0 9
T i m e ( s )
Acceleration(m/
s2)
Figure 32. Predicted acceleration time history at ACC09
0 1 0 2 0 3 0 4 0 5 0- 4
- 3
- 2
- 1
0
1
2
3
4
5A c c e l e r a t i o n t i m e h i s t o r y a t A C C 1 0
T i m e ( s )
Accelera
tion(m/
s2)
Figure 33. Predicted acceleration time history at ACC010