Anisotropic deformation characteristics of geomaterials in a wide strain range

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In this study, a triaxial test apparatus which is composed of a triaxial cell with automated control and measurement system together with measurement units for shear wave velocities is newly developed for the measurements at small strain level. Stability and errors of the system were first evaluated. Stiffness and anisotropy of Toyoura sand at small strain level were measured by performing triaxial tests with small cyclic loading and shear wave shear wave velocity measurement. The results were compared with the results obtained by hollow cylindrical torsion shear tests.If internal measurements were made to avoid bedding error, both LDT and LVDT gave the similarly accurate axial strain values. Errors in volume change measurements should be corrected not only for membrane penetration on the side of the specimen but also for other system compliance. Corrections were also wade for the bedding error at lubrication layer and the gaps between the membrane and endplates. In this test series, enlarged plates were used both at a top cap and a pedestal for lubrication, and the membrane could not be perfectly fit at the corner of the specimen and the plate. Errors in volume change measurements were found to change linearly with the logarithm of the effective confining pressure. It was checked that the small strain stiffness could be determined precisely at a very small strain level of 10^<-5>, if the corrections were made properly.Stiffness and anisotropy of Toyoura sand at small strain level were measured by performing triaxial tests with small cyclic loading and shear wave shear wave velocity measurement. Preliminary test results are presented and compared with the results obtained by hollow cylindrical torsion shear tests. Stress state dependency of small-strain stiffness is discussed.