Reduction of shear moduli by liquefaction in large strain torsional shear

摘要

In order to investigate the liquefaction-induced ground deformation, we conducted a series ofrnundrained cyclic torsional shear tests on saturated Toyoura sand by using a modified torsional shear apparatusrnthat is capable of achieving double amplitude shear strain up to about 100%. Before the undrained cyclic torsionalrnshear tests, the initial values of small strain shear moduli were measured by dynamic measurement. Thernlimiting value of double amplitude shear strain to cause strain localization, which may link to the maximumrnamount of liquefaction-induced ground deformation, was evaluated based on the change in the deviator stressrnduring undrained cyclic torsional loading. The limiting value was found to increase with a decrease in both initialrnsmall strain shear moduli and relative density of the specimen. In addition, we measured tangent shearrnmoduli at the limiting state as well as after strain localization, and evaluated a reduction ratio of shear modulirndue to liquefaction. These characteristics measured by such large strain liquefaction tests may correspond tornactual liquefaction behaviour, and they may be useful in estimating the maximum liquefaction-induced groundrndeformation.