Draft Guidelines for Evaluating Liquefaction Resistance Using Shear Wave Velocity Measurements and Simplified Procedures.
Draft Guidelines for Evaluating Liquefaction Resistance
Using Shear Wave Velocity Measurements and Simplified
Procedures.
(8727 K)
Andrus, R. D.; Stokoe, K. H., II; Chung, R. M.
NISTIR 6277; 134 p. March 1999.
Available from:
National Technical Information Service
(NTIS), Technology Administration, U.S. Department of
Commerce, Springfield, VA 22161.
Telephone:
1-800-553-6847 or 703-605-6000;
Fax: 703-605-6900.
Website: http://www.ntis.gov
Order number: PB99-117897
Keywords:
building technology; earthquakes; in situ measurements;
seismic testing; shear wave velocity; soil liquefaction
Abstract:
Predicting the liquefaction resistance of soil is an
important step in the engineering design of new and the
retrofit of existing structures in earthquake-prone
regions. The procedure currently used in the U.S. and
throughout much of the world to predict liquefaction
resistance is termed the simplified procedure. This
simplified procedure was originally developed by H. B.
Seed and I. M. Idriss in the late 1960s using blow count
from the Standard Penetration Test. Small-strain, shear
wave velocity measurements provide a promising
alternative and/or supplement to the penetration-based
approach. This report presents draft guidelines for
evaluating liquefaction resistance using shear wave
velocity measurements. These draft guidelines were
written in cooperation with industry, researchers and
practitioners, and evolved from workshops in 1996 and
1998. The guidelines outline the development of a
recommended procedure, which follows the general format
of the penetration-based simplified procedure. The
proposed procedure has been validated through case
history data from more than 20 earthquakes and 70
measurement sites in soils ranging from clean fine sand
to sandy gravel with cobbles to profiles including silty
clay layers. Liquefaction resistance curves were
established by applying a modified relationship between
shear wave velocity and cyclic stress ratio for constant
average cyclic shear strain suggested by R. Dobry. These
curves correctly predict moderate to high liquefaction
potential for over 95% of the liquefaction case
histories, and are shown to be consistent with the
penetration-based curves. To further validate the
procedure, additional case histories are needed with all
soil types that have and have not liquefied,
particularly from deeper deposits (depth > 8 m) and from
denser soils (shear wave velocity > 200 m/s) shaken by
stronger ground motions (peak ground acceleration > 0.4
g). The guidelines serve as a resource document for a
final recommended practice, and for practitioners and
researchers involved in evaluating soil liquefaction
resistance.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899