Collaborative Research: Validation of Constitutive and Numerical Modeling Techniques for Soil Liquefaction Analysis

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Soil liquefaction is a pervasive problem during earthquakes that has caused significant and costly damage to civil infrastructure in the US and other parts of the world. Practicing engineers and academics have been using computational models and numerical simulation tools in the design and analysis of geosystems involving liquefiable soils. These tools are highly sophisticated and refined, but they often have been revised following many major past earthquakes to incorporate the lessons learned from post-event observations and investigations. Thus, the validity of these tools is yet to be fully established. The Liquefaction Experiments and Analysis Projects (LEAP) is an international collaboratory to produce a set of high quality experimental data using centrifuge testing, and then to use these data to establish the validity and range of applicability of existing computational models and simulation procedures for soil liquefaction analysis. The collaboratory includes centrifuge facilities at the University of California at Davis, Rensselaer Polytechnic Institute, Cambridge University (UK), Kyoto University (Japan), NCU (Taiwan), Zhejiang University (China), IFSTTAR (France), KAIST and KWater (Korea), and HKUST (Hong Kong). The project leverages the experimental resources at these facilities to complement the testing capabilities in the participating US institutions for investigating a number of challenging problems in which soil liquefaction plays a prominent role.Three consecutive projects (LEAP-2017, -2018, and -2019) are planned which will be used to address three important issues: reproducibility and uncertainty; effects of soil fabric; and effects of biaxial ground motion on soil liquefaction. LEAP-2017 will use improved quality control measures to minimize uncertainties, and an extensive testing program will be designed and conducted to characterize the sensitivity and uncertainty for relatively simple lateral spreading centrifuge tests. LEAP-2018 will produce high quality centrifuge data to enable the assessment of the applicability of computational tools for predicting the influence of fabric and layering. LEAP-2019 will assess the performance of numerical tools against a series of biaxial shaking centrifuge experiments using synthetic and real earthquake motions. Following each LEAP, a workshop will be held to discuss the results of experiments and numerical simulations. The data resulting from this project will be organized, archived and publically released using a new database publication mechanism. The organized data will be useful for (1) future validation efforts, (2) other ongoing liquefaction research, and (3) in geotechnical modeling education. A number of graduate students are involved in the project and will receive unique training opportunities beyond the capabilities of any one institution alone. A Validation Driver Framework (VDF) will be developed to allow modelers as well as practitioners to efficiently validate their codes.