EVALUATION OF LIQUEFACTION RESISTANCE OF CLEAN SANDS BASED ON HIGH-QUALITY UNDISTURBED SAMPLES

High-quality undisturbed samples of clean sands were obtained by in situ freezing methods from a man-made fill, and from natural deposits at three sites in Niigata. Conventional tube samples were also obtained from the sites in Niigata. The spt n-values corrected for a vertical effective stress of 1 kgf/sq cm (98 kpa), n1, of the in situ frozen samples ranged between 2 and 30. Undrained triaxial tests were conducted on cylindrical specimens prepared from the samples after they had been thawed, saturated and consolidated. The results of the field and laboratory tests indicate that: (1) the liquefaction resistance of the high-quality undistrubed samples shows a good correlation with n1 in such a way that the liquefaction resistance increases abruptly as n1 exceeds a certain critical value, which increases with an increase in the number of load cycles; (2) the liquefaction resistance vs n1 relationship of the high-quality undisturbed samples is consistent with the previously published relationship based on field records of liquefaction during earthquakes; and (3) the liquefaction resistance of the tube samples shows a good correlation with n1 over a range between 18 and 30, although the liquefaction resistance is considerably lower than that of the in situ frozen samples. (Author/TRRL)