Hits: 4748
One of the issues of liquefaction arising after the 2011 off the Pacific Coast of Tohoku Earthquake, Japan, is aging effects on liquefaction resistance of sandy deposits. The aging effects of sandy deposits are considered to be strengthening of micro-structure of soil particles through time, and they would be closely related to the small strain shear moduli. In this study, to investigate the relationship between the liquefaction resistance and the small strain shear moduli, undrained cyclic torsional shear tests and dynamic small strain shear moduli measurements were conducted on boiled silty sand which was retrieved in Urayasu city where significant liquefaction occurred in the 2011 earthquake. In order to artificially enhance the micro-structure of soil particles which would correspond to the aging effects, some specimens were subjected to drained cyclic vertical loading after isotropic consolidation. The small strain shear moduli of the specimens were increased by applying drained cyclic vertical loading, and larger liquefaction resistance was obtained with an increase in the small strain shear moduli. However, such enhanced initial soil structure has little direct effect on the large strain characteristics.