Behavior of Granular Soils under Dry and Saturated Conditions in Cyclic Torsional Shear Tests

This paper presents results from drained cyclic torsional shear tests on Toyoura sand and a residual soil under dry and saturated conditions. The relationships of shear strain,   z with shear stress,   z ; normalized shear stress, z z     / ; vertical strain, z  ; and equivalent shear modulus, Geq are compared. The investigation of granular decomposition with respect to its influence on accumulation of vertical strains and shear stiffness were of major interest. It is concluded that the strength and deformation response of granular soils, if decompose with time due to water action, are largely different from what we expect from conventional soils of durable grains. It is anticipated from this study that the laboratory tests on residual soils can provide more reliable and realistic parameters for site characterization and as an input for numerical models.