LEAP-ASIA

LEAP-Asia-2019 Workshop Program

Date: March 13-15, 2019 (Welcome reception at March 13, 2019)

Venue: Kansai University, Osaka, Japan (Takatsuki Muse Campus M804)

For more information, please see below.

LEAP-Asia-2019ProgramV2.pdf

LEAP-Asia-2018 Numerical Simulation Exercise

Objective:

The main objective of the LEAP-Asia-2018 numerical simulation exercise is to help validate the generalized scaling law (Iai et al., 2005). To this end, this numerical simulation exercise is planned to assess the capability of constitutive models and the numerical modeling techniques in:

1. capturing the response of saturated liquefiable soils (such as Ottawa F-65 sand) to cyclic shearing at different levels of confining stress, and

2. simulating potential effects of confining stresses on the lateral spreading of liquefiable soils caused by earthquakes.


Phase I of the numerical simulation exercise:

The first phase of this simulation exercise is to allow the participating teams to calibrate their constitutive models using the results of recently completed torsional shear tests (for Dr = 50% and 60% under an initial effective confining stress of 100 kPa) at Kyoto University (KyU) and the direct simple shear tests (for Dr ~ 71% under an initial effective vertical stress of 100 kPa and Dr ~69% under 40 kPa) at the George Washington University (GWU).

The element tests mentioned above provide new datasets that complement the monotonic and cyclic traixial shear tests reported by Vasko (2015), Vasko et al. (2018), monotonic and cyclic simple shear tests by Bastidas (2016) and Bastidas et al. (2017), and cyclic triaxial tests by El Ghoraiby, Park, and Manzari (2017 and 2018). These tests were previously made available to the numerical simulation teams that participated in the numerical simulation of LEAP-2017 project. The new datasets will be made available to all the numerical simulation teams that participate in LEAP-Asia-2018 project.

The timeline for this phase of the project is as follows:

1. All the element test data will be made available on DesignSafe to the numerical simulation teams by December 5th. These are as follows:

・LEAP-2015 GWU LABORATORY TESTS: https://doi.org/10.17603/DS2TH7Q

・LEAP-2017 GWU LABORATORY TESTS: https://doi.org/10.17603/DS2210X (cyclic triaxial shear tests for Dr = 71%, 87%, and 97% at GWU)

・LEAP-2018 GWU CYCLIC SIMPLE SHEAR: https://doi.org/10.17603/DS2HX3H (cyclic direct simple shear tests for Dr = 71% and 69% at GWU)

・LEAP-2018 KyU CYCLIC TORSIONAL SHEAR: https://doi.org/10.17603/DS2D40H (cyclic torsional shear tests for Dr = 50% and 60% at KyU).

2. The participating teams will be requested to simulate a selected number of the provided test data and liquefaction strength curves that are obtained from cyclic direct simple shear tests and cyclic torsional shear tests. The key tests to be simulated are the cyclic torsional shear test for Dr = 50% and 60% (under an initial effective confining stress of 100 kPa). It is required to compare the simulated stress-paths and stress-strain responses to the experimental results reported by KyU. If time allows, it is desirable to show the validity of constitutive models for the other experimental results having higher relative densities.

The numerical simulation team will submit the results of their element test simulations and comparisons with those of the provided element tests in form of a detailed report by January 11th, 2019.


Phase II of the numerical simulation exercise:

The second phase of the simulation exercise consists of the numerical (Type-C) simulation of centrifuge tests that will be conducted as part of LEAP-Asia-2018 centrifuge modeling campaign.

The main steps of the second phase of numerical simulations are as follows:

1. Results of two sets of centrifuge tests (known as Model A tests in LEAP-Asis-2018) will be provided to the numerical simulation teams. Some of the tests were performed as part of LEAP-2017 project. Detailed information including the achieved base excitation, detailed information about the centrifuge specimen (density of the prepared specimen, as-built geometry, location of the sensors, etc.) and the measured pore water pressures,

accelerations, and displacements can be used by the numerical simulation teams to fine tune the parameters of their constitutive models and the key parameters of their numerical simulation platform (damping ratio, permeability, etc.).

2. The achieved base excitations, density of the soil specimen, and locations of the sensors in centrifuge tests to be conducted as Model B tests for LEAP-Asia-2018 will be provided (including the complete set of the experimental results) to the numerical modeling teams, and they will be asked to simulate the results of these tests in terms of time histories of excess pore pressure, accelerations, and lateral displacements at selected locations. The Model B tests have the same prototype and model sizes as the corresponding Model A tests, but the centrifugal acceleration (η) is scaled in accordance with the generalized scaling law (Iai et al., 2005) as shown in Fig. 1. Since the centrifugal accelerations in the Model B tests at a few facilities are much lower than that in the Model A tests, the model parameters might need to be fine-tuned to take into account the low confining stress effect on liquefaction strength. Such issues (revision of the parameters and their effects on liquefaction strength curves reported in Phase I) should be clearly documented in the reports submitted by the numerical simulation teams.

The timeline of the second phase of the numerical simulations is as follows:

1. All the necessary data regarding Model-A tests will be provided to the numerical modelers on December 10th, 2018.

2. All the information regarding Model-B tests will be provided to the numerical simulation teams before December 17th, 2018.

3. The numerical simulation teams will be requested to submit the results of their simulations by February 8th, 2019.

References:

Bastidas, A.M.P. (2016). Ottawa F-65 Sand Characterization. PhD Dissertation, University of California, Davis.

Bastidas, A.M.P., Boulanger, R.W., Carey, T., DeJong, J. (2017), Ottawa F-65 Sand Data from Ana Maria Parra Bastidas, https://datacenterhub.org/resources/ottawa_f_65.

El Ghoraiby, M.A., Park, H., and Manzari, M.T. (2017). LEAP 2017: Soil Characterization and Element Tests for Ottawa F65 Sand. The George Washington University, Washington, DC.

El Ghoraiby, M.A., Park, H., and Manzari, M.T. (2018). Physical and Mechanical Properties of Ottawa F65 Sand. LEAP-UCD-2017 Proceedings, Springer.

El Ghoraiby, M.A., and Manzari, Majid, (2018), "LEAP-2018 - Stress-strain response of Ottawa F65 sand in Cyclic Simple Shear", DesignSafe-CI [publisher], Dataset, doi:10.17603/DS2HX3H

Korre, E., Abdoun, T., and Zeghal, M. (2018). “Verification of the Repeatability of Soil Liquefaction Centrifuge Testing at Rensselaer.” LEAP-UCD-2017 Proceedings, Springer.

Iai, S., Tobita, T., Nakahar, T. (2005). “Generalised Scaling Relations for Dynamic Centrifuge Tests.” Geotechnique, Volume 55, Issue 5, June, pp. 355-362.

Ueda, Kyohei, (2018-12-04), "LEAP-Asia-2018: Stress-strain response of Ottawa sand in Cyclic Torsional Shear Tests" , DesignSafe-CI [publisher], Dataset, doi:10.17603/DS2D40H.

Vasko, A. (2015). An Investigation into the Behavior of Ottawa Sand through Monotonic and Cyclic Shear Tests. Masters Thesis, The George Washington University.

Vasko a., ElGhoraiby, M. A., and Manzari, M. T. (2018). Charaterization of Ottwa Sand.

DesignSafe, https://doi.org/10.17603/DS2TH7Q.