The Earthquake Engineering Online Archive

Influence of seismic history on the liquefaction characteristics of sands

Seed, H. Bolton; Mori, Kenji; Chan, Clarence K.

UCB/EERC-75/25, Earthquake Engineering Research Center, University of California, Berkeley, 1975-08, 33 pages (475/S41/1975)

This report describes studies which were conducted to clarify the effects of seismic history on the liquefaction characteristics of saturated sands. It has been shown both analytically and experimentally that deposits of sand subjected to low magnitude earthquakes, which are not sufficiently strong to cause liquefaction, will develop an increased resistance to liquefaction in subsequent earthquakes even though they may undergo no significant change in density. This increased resistance may be due to changes in structure of the sand grain system or an increase in the lateral earth pressure coefficient, K subscript o. Accordingly, in order to determine the liquefaction characteristics of a sand, it is necessary to perform tests on samples having the same density and structure as the in-situ material and conduct the tests, whenever possible, with the correct insitu value of K subscript o. In practice this is best achieved at the present time by performing tests on undisturbed samples which retain the same density and structure as the in-situ material and applying analytical corrections for any deviation from the desired value of K subscript o in the test program. The study also indicates that the standard penetration resistance (or any in-situ measure of penetration resistance) is likely to provide a reasonable index of the liquefaction characteristics of a saturated sand deposit and available data on field performance has been summarized to develop a correlation between penetration resistance and the cyclic stress ratio at which liquefaction has been found to occur in the field. By combining the results of appropriate test programs as described above with analytical evaluations of the shear stresses developed by any given earthquake in a sand deposit, and utilizing the correlations between field performance and relative density as a supplementary guide to probable future performance, it should be possible to arrive at a reasonably good evaluation of the liquefaction potential and the associated potential deformations of a sand deposit. However, it is apparent that good judgment must continue to be an essential ingredient of such evaluations at the current state of knowledge.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-75-25.pdf (1 MB)