NEESR-CR: Evolutionary Intensity Measures for More Accurate and Informative Liquefaction Hazard Evaluation

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This award is an outcome of the NSF 09-524 program solicitation ''George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)'' competition and includes the University of Washington (lead institution), the University of Alaska, Fairbanks (subaward), and the University of Portland (subaward). This project will utilize the NEES equipment site at Rensselaer Polytechnic Institute.Soil liquefaction is an important seismic hazard that has caused extensive damage to buildings, bridges, dams, wharves, and lifelines in past earthquakes. It has caused buildings to sink into the ground, bridges and dams to collapse, and buried tanks and pipelines to pop out of the ground. It has also caused devastating landslides in both natural and man-made ground, and has destroyed major port facilities.Soil liquefaction first sprang to the attention of engineers following large earthquakes in Alaska and Japan in 1964. Engineers realized that similar earthquakes occurring in more heavily populated and industrialized areas of the United States, such as the Los Angeles, San Francisco, Seattle, and Portland areas, could cause liquefaction that would kill people and produce billions of dollars in economic losses. Geotechnical engineers went to work immediately to produce procedures for evaluating liquefaction hazards. While a number of useful and important refinements have been made, the basic procedures used today are the same as those developed 30-40 years ago, despite greatly improved understanding of the liquefaction process.In current practice, the complex, transient ground motion produced by an earthquake is typically represented by a single point "its maximum value" and a measure of the duration of the motion. Such peak-amplitude-based parameters provide no information on whether liquefaction occurs early or late in an earthquake, which limits their effectiveness in predicting the effects of liquefaction. The use of evolutionary measures of ground motion intensity, i.e., measures that build up with time over the duration of a ground motion, which would allow the missing dimension of time to be brought into the liquefaction hazard evaluation problem, will be investigated in this project. The relationship between soil liquefaction and a variety of different measures of ground motion intensity will be investigated. The research will generate a large amount of experimental validation data using centrifuge model and element testing with realistic, transient loading histories. The experiments performed using these motions will provide a much more severe, and realistic, test of the pore pressure and permanent deformation prediction capabilities of ground motion intensity measures than the types of tests for which data is currently available. This project will provide a basis for the development of liquefaction hazard evaluation procedures that are more accurate and that provide important additional information than currently used procedures. Such procedures will lead to improved public safety and the more efficient use of retrofitting/remediation resources. An existing educational website devoted to soil liquefaction will be substantially updated and expanded. We will also interact with organizations such as the Alaska Native Science and Engineering Program, the Alaska Summer Research Academy for grade 8-12 students, and the Oregon Museum of Science and Industry to bring the problem of liquefaction and the benefits of this research to students who would not normally be exposed to it. Data from this project will be archived and made available to the public through the NEES data repository.