Ing Civil

Preface
Evaluation of soil liquefaction resistance is an important aspect of geotechnical engineering practice. To update
and enhance criteria that are routinely applied in practice, workshops were convened in 1996 and 1998 to gain
consensus from 20 experts on updates and augmentations that should be made to standard procedures that have
evolved over the past 30 years. At the outset, the goalwas to develop this state-of-the-art summary of consensus
recommendations. A commitment was also made to those who participated in the workshops that all would be
listed as co-authors. Unfortunately, the previous publication of this summary paper (April 2001) listed only the
co-chairs of the workshop, Profs. Youd and Idriss, as authors; the remaining workshop participants were
acknowledged ina footnote. In order to correct this error and to fully acknowledge and credit those who
significantly contributed to the work, this paper is being republished in its entirety, at the request of the journal’s
editors, with all the participants named as co-authors. All further reference to this paper should be to this
republication. The previous publication should no longer be cited. Also,several minor errors are corrected in
this republication.

LIQUEFACTION RESISTANCE OF SOILS: SUMMARY REPORT FROM THE
1996 NCEER AND 1998 NCEER/NSF WORKSHOPS ON EVALUATION
a
OF LIQUEFACTION RESISTANCE OF SOILS
By T. L. Youd,1 Chair, Member, ASCE, I. M. Idriss,2 Co-Chair, Fellow, ASCE,
Ronald D. Andrus,3 Ignacio Arango,4 Gonzalo Castro,5 John T. Christian,6
Richardo Dobry,7 W. D. Liam Finn,8Leslie F. Harder Jr.,9 Mary Ellen Hynes,10
Kenji Ishihara,11 Joseph P. Koester,12 Sam S. C. Liao,13 William F. Marcuson III,14
Geoffrey R. Martin,15 James K. Mitchell,16 Yoshiharu Moriwaki,17 Maurice S. Power,18
Peter K. Robertson,19 Raymond B. Seed,20 and Kenneth H. Stokoe II21

ABSTRACT: Following disastrous earthquakes in Alaska and in Niigata, Japan in 1964, Professors H. B. Seed
and I. M.Idriss developed and published a methodology termed the ‘‘simplified procedure’’ for evaluating
liquefaction resistance of 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 theprocedure 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 soils. In 1996 a workshop sponsored by the National Center for Earthquake
Engineering Research (NCEER) was convened by Professors T. L. Youd and I. M. Idriss with 20 experts to
review developments over the previous 10 years.The purpose was to gain consensus on updates and augmentations to the simplified procedure. The following topics were reviewed and recommendations developed: (1)
criteria based on standard penetration tests; (2) criteria based on cone penetration tests; (3) criteria based on
shear-wave velocity measurements; (4) use of the Becker penetration test for gravelly soil; (4) magnitude scaling
factors;(5) correction factors for overburden pressures and sloping ground; and (6) input values for earthquake
magnitude and peak acceleration. Probabilistic and seismic energy analyses were reviewed but no recommendations were formulated.

a
This Summary Report, originally published in April 2001, is being
republished so that the contribution of all workshop participants as authors can be officiallyrecognized. The original version listed only two
authors, plus a list of 19 workshop participants. This was incorrect; all
21 individuals should have been identified as authors. ASCE deeply regrets the error.
1
Prof., Brigham Young Univ., Provo, UT 84602.
2
Prof., Univ. of California at Davis, Davis, CA 95616.
3
Prof., Clemson Univ., Clemson, SC 29634-0911; formerly, Nat. Inst.
of...