D11

Validation of Numerical Predictions of Lateral Spreading Based on “Hollow-Cylinder Torsional
Shear Tests” and a Large Centrifuge-Models Database〇Ruben R. VARGAS, Kyohei UEDA, Ryosuke UZUOKAstudy), aiming to study the dynamic response of a

1．Introduction
During the past 40 years, efforts and developments
in computational modeling of geo-materials havesaturated sloping ground under different relative
densities (Dr), and Peak Accelerations (PGA).

contributed to increasing the accuracy of prediction ofthe dynamic response of soil systems. However,despite of the efforts, exercises of verification andvalidation (V&V) of numerical simulations are
required to enhance the reliability of numericalmodels.

Inthissense,anewinternational

collaborative project (named “LEAP”) was developed,

Figure 1. Schematic diagram of the main steps of theaiming a re-assessment of the reliability of modern

validation exercise

numerical techniques in the analysis of liquefaction
related problems1).
The main objective of this work is to validate thecapabilities of the “Strain Space Multiple MechanismModel”2) to simulate the lateral spreading phenomena
under a diverse range of densities and input motions.
Figure 1 shows a schematic diagram of the main
steps followed in the validation process.

Figure 2. Model Dimensions – Model Scale

Kutter et. al3) found that, for the lateral spreading

2．Physical Modelingphenomena, the final surface displacements (Ux) are

2.1．Model Specifications

primarily a function of the intensity of shaking and theAs described by Kutter et. al3), a uniform-density,

relative density of the sand. Based on this, a

20 m long, 4 m deep at center, and 5 degrees sloping

correlation between Ux, PGA, and Dr, was developed;

deposit of Ottawa F-65 Sand inside a rigid container,

aiming that this correlation will serve as the basis forwas specified for the LEAP Exercises. Figure 2 shows

the validation process. As an attempt to estimate thethe geometry, dimensions, and instrumentation of thevariability in the tests, as seen in Figure 3, the uppertarget models in model scale. The input motion

and lower bounds for a 95% probability wereconsisted of a ramped sinusoidal 1 Hz wave.

estimated, assuming a Gaussian Distribution.

2.2．Correlation and Variability Estimation

3．Element Tests

As part of LEAP Project, forty-eight tests wereIn order to study the mechanical properties ofdeveloped in ten different centrifuge facilities all overOttawa F-65 Sand, a series of Hollow Cylinder

the world (eight of them developed as part of thisDynamic Torsional Shear Tests for four differentrelative densities (Dr=50%, 60%, 70%, and 80%),displacements. As an example, Figure 8 shows awere conducted under a wide range of Cyclic Stresscomparison between displacements obtained by theRatio

numerical(CSR)

values,aimingtoestimate

thecorresponding liquefaction resistance curves (LRC).

simulations,andtheexperimental

displacements (i.e. based on the correlation), for
Dr=60%. This figure includes a comparison between
the mean values (i.e. 50% probability) and theupper/lower

boundaries

corresponding

to

95%

probability, for the three scenarios of variability.

Figure 3. Confidence Bounds for the Ux-Dr-PGA Correlation

4．Numerical Model
4.1．Element Tests Simulations
Based on a parametric study, the seventeen
parameters of the model (for each density under

Figure 5. Computed displacements vs Results obtained in thestudy) were estimated following an iterative procedure,

estimated correlation, for Dr = 60%

taking as a primary reference the LRC for γDA=7.5%.

6．Conclusions

Additionally, as for the input variability of the model,



Based on LEAP Tests, a correlation that provides ait was considered as variations in the simulated LRC,

reliable characterization of the response wasunder three different scenarios.

developed; it was shown that it can be used as a

4.2．Physical Model Simulations

reliable baseline in the development of current andBased on the characteristics of the models, andusing the calibrated parameters, the analysis was

future V&V processes of liquefaction models.
For the median response, it has been shown that if

carried out under 2-D plane-strain conditions, aiming

the model parameters are calibrated based on

to simulate the models in prototype scale. Figure 4

high-quality laboratory tests, a good agreement canshows the mesh and the boundary conditions.

be obtained for PGA values lesser than 0.25g.
For 95% probability, the confidence bounds of thecomputed displacements are located between theconfidence bounds of the experimental outcomes,for PGA values lesser than 0.25g.

Figure 4. FEM Mesh and Boundary Conditions

5 ． Comparison among Physical and Numerical
ModelsHundreds of numerical models were developed inReferences
1) Manzari MT et. al. (2015) – “LEAP projects:
Concept and challenges” Geotechnics for Catastrophic
Flooding Events; 109-116, CRC Press.

order to replicate the combinations of Dr-PGAeff for2) Iai S et.al. (2011) “Dilatancy of granular materials

which the correlation was developed (i.e. 50% <Dr<in a strain space multiple mechanism model”. IJNAMG,80%, and 0.1g < PGAeff < 0.35g). The uncertainty of35(3)the LRC was propagated through the model by means3) Kutter BL et. al. (2018) “Twenty-Four Centrifugeof Monte-Carlo simulations, in order to obtain theTests to Quantify Sensitivity of Lateral Spreading to Dr

median trend and the variability of the computedand PGA” Geot. Earthquake Eng. and Soil Dyn. V.