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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 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)


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)


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


T i m e ( s )

RU


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


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


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


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


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


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


T i m e ( s )

RU


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


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


T i m e ( s )

Acceleration(m/

s2)


0 1 0 2 0 3 0 4 0 5 0- 4

- 3

- 2

- 1

0

1

2

3


T i m e ( s )

Acceleration(m/

s2)


0 1 0 2 0 3 0 4 0 5 0- 4

- 3

- 2

- 1

0

1

2

3


T i m e ( s )

Acceleration(m/

s2)



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0 1 0 2 0 3 0 4 0 5 0- 3

- 2

- 1

0

1

2

3

4


T i m e ( s )

Acceleration(m/

s2)


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)


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)



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0 1 0 2 0 3 0 4 0 5 0- 4

- 3

- 2

- 1

0

1

2

3

4


T i m e ( s )

Acceleration(m/

s2)


0 1 0 2 0 3 0 4 0 5 0- 5

0


T i m e ( s )

Acceleration(m/

s2)


0 1 0 2 0 3 0 4 0 5 0- 4

- 3

- 2

- 1

0

1

2

3

4


T i m e ( s )

Accelera

tion(m/

s2)


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