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Proceedings of the International Conference on
Advances and New Challenges in Earthquake
Engineering Research, Hong Kong Volume
EVALUATION OF DYNAMIC SOIL PROPERTIES AND
LIQUEFACTION POTENTIAL BY SEISMIC PIEZOCONE TESTS
T. Liao and P.W. Mayne
Georgia Institute of Technology, School of Civil & Environmental Engineering,
Atlanta, GA 30332-0355 USA
ABSTRACT
Seismic piezocone tests (SCPTu) provide an expedient and efficient means to obtain site-specific
information on the soil stratigraphy, dynamic soil properties, and ground liquefaction susceptibility,
since five separate readings are obtained hi the same sounding: cone tip stress (q-r), sleeve friction (f s ),
penetration porewater pressure (ut>), dissipation-time recordings (tso), and shear wave velocity (V s ). The
shear wave data are used to determine the small-strain stiffness that is required in ground amplification
analyses (e.g., SHAKE, DESRA, DEEPSOIL). Layering and soil types are evaluated from the
penetration readings to detect soils that are prone to liquefaction (i.e., sands, silty sands). The
liquefaction potential is assessed using two independent readings from the sounding that are
normalized for the effects of effective confining stress levels (q-n and V s i). Illustrative results from
seismic piezocone tests at a paleoliquefaction site in the New Madrid Seismic Zone in midwestern
USA are presented.
INTRODUCTION
Dynamic soil properties and liquefaction potential are among the major concerns in evaluating the level
of ground shaking and disruption that might occur during earthquakes. Key dynamic soil properties
include the small-strain shear modulus (Gmax), Poisson's ratio (v), damping ratio (D s ) (Woods, 1978;
Campanella, 1994). Parameters related to the liquefaction potential of soils are addressed separately
because of their unique destructive nature. Dynamic soil properties and liquefaction potential can be
evaluated by laboratory techniques, such as strain-rate-test, resonant column, ultrasonic pulse, cyclic
(triaxial, simple shear, torsional shear) test, bender-element, and shake table. Although the lab tests are
versatile and can provide the desirable dynamic soil properties, undisturbed samples of sandy soils are
either very expensive or impossible to obtain. Furthermore, after the soil samples are taken from the
field, their in-situ state cannot be fully recovered in the lab, leading to errors hi test results. For these
reasons, field testing is becoming more popular for site characterization in seismic areas and the
evaluation of dynamic soil properties and liquefaction potential.
The most widely used field technique is the standard penetration test (SPT), but it is not realistic for the
single N-value from this test to fulfill the task to provide the many parameters needed for engineering