Aging Effects on Small Strain Shear Moduli and Liquefaction Properties of in-situ Frozen and Reconstituted Sandy Soils

In order to investigate the effects of different geological ages on liquefaction properties of sandy deposits, a series of undrained cyclic triaxial tests was performed on three kinds of in-situ frozen and their reconstituted samples which were retrieved from Holocene (Tone-river sand) and Pleistocene (Edo-river B and C sands) deposits. The specimens were subjected to isotropic consolidation at a specified confining stress which is equivalent to the in-situ overburden stress at the depth of sampling, and small strain shear moduli were measured before and during the undrained cyclic loading tests. The liquefaction properties and the small strain shear moduli were affected by not only the natural aging effect of the specimen but also the inter-locking effect that was enhanced by applying drained cyclic loading before the undrained cyclic loading tests. During liquefaction, different tendencies of degradation in the small strain shear moduli which would reflect the aging effects of the specimen were observed between Tone-river Holocene sand and Edo-river B and C Pleistocene sands. The applicability of reconstituted samples as substitutes for in-situ frozen samples was confirmed with Tone-river Holocene sand that has no cementation effect between soil particles, whereas it seems difficult to simulate fully the liquefaction behaviour of Edo-river B and C Pleistocene sands which have higher cementation effect.