Dynamic deformation characteristics of dry and saturated sands under cyclic loadings

In this study, dynamic deformation characteristics of sands under dry, saturated drained and undrained conditions were investigated at small to intermediate strains using the Stokoe-type torsional shear tests. The equipment was modified to saturate the specimen and to maintain the B-value above 0.99 during the test. Two types of sands, Geumgang sand from Korea and Toyoura sand from Japan, were collected and tested at various drainage conditions, densities, and confining pressures. Based on the test results, the dynamic deformational characteristics, G and D, and/or pore-water pressure were measured with strain amplitude and number of loading cycles. Variations in G and D at small (gamma(c)<10-3%) to medium (10(-3)%<gamma(c)<10(-1)%) strains were characterized under various conditions, and test results were intensively compared considering drainage conditions, void ratio, and isotropic confining pressure.