Abstract: Undrained cyclic triaxial tests are conducted on Zhanjiang structured clay under different static deviatoric stresses. The internal connection among dynamic deformation, dynamic pore pressure, dynamic strength and structure characteristics are studied. It is shown that the sudden destruction of structured clay under dynamic loads exhibits a feature of brittle failure; and the higher the static deviatoric stress, the smaller the failure strain. The trend of critical dynamic stress with deviatoric stress first increases and then decreases, and the critical dynamic stress has a peak value as the deviator stress decreases. There exists a threshold for the influence of static deviatoric stress on the dynamic characteristics of structured clay. If the static deviatoric stress is below the threshold, the deformation of the clay is restrained as a result of the improvement of the critical dynamic stress and the dynamic strength by the compaction effect of the static deviatoric stress. With the increasing of static deviatoric stress, however, the critical dynamic stress and dynamic strength decrease due to the damage of soil structure. The dynamic pore pressure of structured soil is slower than that of general soil, thus, and it drops after soil fails. The initial shear stress can increase the dilatancy.

Key words: structured clay, static deviator stress, dynamic deformation, critical dynamic stress, dynamic strength, dynamic pore pressure