Keywords

1 Introduction

LEAP (Liquefaction Experiments and Analysis Project) is an international joint research project to discuss the modeling of the centrifuge test and numerical modeling of liquefaction.

Summary of centrifuge experiments is listed in Tables 18.1 and 18.2. In this chapter, numerical simulation of phase II was performed for “KyU_A_2_1”, “RPI_A_A1_1,” “UCD_A_A2_1,” “KyU_A_B2_1,” and “RPI_A_B1_1” (Fig. 18.1).

Table 18.1 Summary of centrifuge experiments, Model A in LEAP-ASIA-2018
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Table 18.2 Summary of centrifuge experiments, Model B in LEAP-ASIA-2018
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Fig. 18.1
2 schematic diagrams of the centrifuge model. They have connected components of a rigid container, a water table to cover the sand during spinning, and separate sections of A A with various labeled parts and dimensions. Section A A in A has a circular shape, and the main section in B has a log spiral shape.

Schematic for LEAP-ASIA-2018 centrifuge model tests: (a) Sectional drawing for shaking parallel to the axis of the centrifuge; (b) Sectional drawing for shaking in the plane of spinning of the centrifuge

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2 Constitutive Model of Soils

We conducted element test simulation and 2D analysis for the numerical simulation exercises. The 2D analysis was performed by using FLIP ROSE Ver7.4.2. In this program, a strain space multiple mechanism model (Iai et al., 1992, 2011) is used.

The model in FLIP ROSE is based on the multiple mechanism model (Towhata & Ishihara, 1985). In this model, the stress-strain relationship in each arbitrary shear direction was modeled as a hyperbolic relationship. The cocktail glass model is the most advanced model for liquefaction in FLIP ROSE. In this model, the dilatancy model is given as the sum of contractive part and dilative part.

3 Detailed Specification of Numerical Simulation (FE Analysis)

3.1 Phase I of Numerical Simulation

We conducted the simulation exercise to calibrate constitutive models using the results of torsional shear tests (for Dr = 50% and 60% under 100 kPa) Tables 18.3 and 18.4 list the parameters of the strain space multiple mechanism model. The most of parameters were set by various tests. The parameters for dilatancy were decided by trial-and-error. Figure 18.2, 18.3, 18.4, 18.5, 18.6 and 18.7 show the results of the simulation of torsional shear tests.

Table 18.3 Parameters for soil
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Table 18.4 Parameters for dilatancy
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Fig. 18.2
A scatterplot of shear stress ratio versus the number of cyclic loads. It plots the color gradient circles of D r at 50% and D r at 60% above, on, and below the concave up, decreasing curves of computated results. It also has gamma D A = 7.5%.

Results of the simulation of torsional shear tests (for Dr = 50% and 60%)

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Fig. 18.3
2 sets of 2 double line graphs of shear stress tau versus shear strain gamma and mean effective stress p prime where shear stress ratio r = 0.19 and 0.15, respectively. All 4 graphs plot the overlapping and intersecting measured and computed lines as S-shaped curves in the first, and fluctuating curves in the second.

Results of the simulation of torsional shear tests (for Dr = 50%). (a) Shear stress ration r = 0.19; (b) Shear stress ration r = 0.15

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Fig. 18.4
2 sets of 2 double line graphs of shear stress tau versus shear strain gamma and mean effective stress p prime where shear stress ratio r = 0.13 and 0.10, respectively. All 4 graphs plot the overlapping and intersecting measured and computed lines as S-shaped curves in the first, and fluctuating curves in the second.

Results of the simulation of torsional shear tests (for Dr = 50%). (a) Shear stress ration r = 0.13; (b) Shear stress ration r = 0.10

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Fig. 18.5
2 sets of 2 double line graphs of shear stress tau versus shear strain gamma and mean effective stress p prime where shear stress ratio r = 0.20 and 0.18, respectively. All 4 graphs plot the overlapping and intersecting measured and computed lines as S-shaped curves in the first, and fluctuating curves in the second.

Results of the simulation of torsional shear tests (for Dr = 60%). (a) Shear stress ration r = 0.20; (b) Shear stress ration r = 0.18

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Fig. 18.6
2 sets of 2 double line graphs of shear stress tau versus shear strain gamma and mean effective stress p prime where shear stress ratio r = 0.15 and 0.13, respectively. All 4 graphs plot the overlapping and intersecting measured and computed lines as S-shaped curves in the first, and fluctuating curves in the second.

Results of the simulation of torsional shear tests (for Dr = 60%). (a) Shear stress ration r = 0.15; (b) Shear stress ration r = 0.13

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Fig. 18.7
2 double line graphs of shear stress tau versus shear strain gamma and mean effective stress P prime where the shear strain ratio r is 0.12. The first graph plots the overlapping and intersecting measured and computed lines as S-shaped curves. The second one plots the lines as fluctuating curves.

Results of the simulation of torsional shear tests (for Dr = 60%). (a) Shear stress ration r = 0.12

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4 Conclusions

This chapter presents LEAP-ASIA-2018 Type-B Simulations. In this chapter, we conducted effective stress analysis by using FLIP ROSE.