Behavior of anisotropic clays under cyclic loading using the true triaxial device

A laboratory experimental investigation was performed to study the behavior of soft clays under dynamic loading conditions. The experiments were conducted in a flexible boundary true triaxial device. The vertical sinusoidal one way cyclic loads were applied at 0.25 Hz., which represents typical ocean wave frequency.; The soil samples were prepared in the laboratory from commercially available kaolinite clay and silica silt. Two types of samples with plasticity indices of 12 and 16 were produced from consolidating the slurry of clay-silt mixtures under two different preconsolidation pressures in the consolidation box.; The effects of the principal stress rotation, the intermediate principal stress and the preconsolidation stress on the response of the samples were investigated.; The results revealed that for the normally consolidated soil the strength and the induced cyclic pore water pressure changed with the increasing of the rotation angle of the principal stresses {dollar}Psisb{lcub}sigma{rcub}.{dollar} When the intermediate principal stress {dollar}sigmasb2{dollar} was increased, the strength, the induced cyclic pore water pressure and the deformation in the minor stress direction increased. The induced pore water pressure was positive. The samples with PI = 12 were stronger than the samples with PI = 16. Also the overconsolidated samples behaved different than the normally consolidated specimens. Though the strength was higher, however it decreased with the increase of {dollar}Psisb{lcub}sigma{rcub}.{dollar} The induced cyclic pore water pressure was also lower. The influence of {dollar}sigmasb2{dollar} was similar to that on normally consolidated samples. Overconsolidated samples with higher PI were found stronger, and their tendency to generate negative pore water pressure was higher.; This investigation also demonstrated the capabilities of the true triaxial device in applying cyclic loading and measuring the deformation and pore water pressure response of the samples. The results of this investigation provide a data base for use by the geotechnical research community in developing the constitutive models of anisotropic soft clays.