Liquefaction resistance of soils: Summary report from the 1996 NCEER and 1998 NCEER/NSF workshops on evaluation of liquefaction resistance of soils

Following disastrous earthquakes in Alaska and in Niigata, Japan in 1964, P rofessors H. B. Seed and I. M. Idriss developed and published a methodology termed the "simplified procedure" for evaluating liquefaction resistance o f soils. This procedure has become a standard of practice throughout North America and much of the world. The methodology which is largely empirical, has evolved over years, primarily through summary papers by H. B. Seed and his colleagues. No general review or update of the procedure has occurred, however, since 1985, the time of the last major paper by Professor Seed and a report from a National Research Council workshop on liquefaction of soil s. In 1996 a workshop sponsored by the National Center for Earthquake Engin eering Research (NCEER) was convened by Professors T. L. Youd and I. M. Idr iss with 20 experts to review developments over the previous 10 years. The purpose was to gain consensus on updates and augmentations to the simplifie d procedure. The following topics were reviewed and recommendations develop ed: (1) criteria based on standard penetration tests; (2) criteria based on cone penetration tests; (3) criteria based on shear-wave velocity measurem ents; (4) use of the Pecker penetration test for gravelly soil; (4) magnitu de scaling factors; (5) correction factors for overburden pressures and slo ping ground; and (6) input values for earthquake magnitude and peak acceler ation. Probabilistic and seismic energy analyses were reviewed but no recom mendations were formulated.