Workshop on Evaluation of Liquefation Resistane of Soils

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ABSTRACT: CMS-9816185, Leslie Youd, Brigham Young U.Over the past twenty-five years, a procedure, termed the "simplified procedure", has evolved to evaluate the seismic liquefaction resistance of soils: it has become the standard of practice in North America and throughout much of the world. This procedure has been corrected and augmented periodically since then. In 1985, Professor Robert Whitman convened a workshop at MIT on behalf of the National Research Council (NRC), in which thirty-six experts and observers thoroughly reviewed the state-of-knowledge and the state-of-the-art for assessing the liquefaction hazard. That workshop produced a report (NRC, 1985) that has become a widely used standard and reference for liquefaction hazard assessment.No general review or update of the simplified procedures was made following the 1985 workshop until a workshop was convened in January 1996. At that meeting, twenty experts reviewed developments since 1985, in order to arrive at a consensus on improvements that could be recommended for engineering practice. The proceedings were published by the sponsor, the National Center For Earthquake Engineering Research, as Technical Report NCEER 97-0022. Consensus was achieved on several, but not all, proposed enhancements to the state of the art. For example, liquefaction resistance procedures based on cone penetration test (CPT) data were endorsed by several key members of the workshop, but not all. This tool is widely used in geotechnical engineering practice and a consensus statement from the workshop group on CPT methodologies is badly needed. Subsequent to this workshop, several of the participants tested the CPT procedures discussed at the workshop, and the results obtained are considered to be sufficient to overcome past concerns.A major goal of the second meeting is to evaluate these additional results, and to gain a consensus on CPT procedures. Additional issues where enhanced recommendations may be possible include: fines-content corrections, magnitude scaling factors, and correction for high overburden pressures. The objective of the reconvened workshop is to produce consensus revisions to the Summary Report, and to prepare a final draft for submission to a major journal for broad dissemination to the geotechnical engineering profession.