Impacts of Initial Deviator Stress and Cyclic Confining Pressure on Mechanical Behaviors of Ningbo Clay under Cyclic Loading

The development of both accumulated axial strain and excess pore-water pressure under cyclic triaxial tests with and without cyclic confining pressure was the focus of the investigation. The effects of factors, such as initial deviator stress, and cyclic confining pressure, were studied. The test results indicated that, compared with the results of cyclic triaxial tests with constant confining pressure, the accumulated axial strain decreased by 19.4% and 23.8% when the slopes of the stress path were 1.0 and 1.5, respectively. The cyclic confining pressure limited the deformation of soils in cyclic triaxial tests with variable confining pressures. Additionally, the development of accumulated axial strain was significantly influenced by initial deviator stress. The accumulated axial strain ratio of initial deviator stress to without initial deviator stress increased from 1.958 to 3.778 as the initial deviator stress ratio increased from 0.05 to 0.125. On the other hand, the maximum excess pore-water pressure increased as the cyclic confining pressure increased, while the minimum excess pore-water pressure hardly changed. Both maximum and minimum excess pore-water pressures remained approximately constant until the initial deviator stress ratio was 1.0 and decreased when the initial deviator stress ratio exceeded 1.0. Besides that, an empirical formula for accumulated axial strain considering the effects of initial deviator stress and cyclic confining pressure was obtained.

Automated summary

The cyclic confining pressure has a limiting effect on soil deformation in cyclic triaxial tests; initial deviator stress has a significant impact on the development of axial strain; the maximum and minimum excess pore-water pressures decrease when the initial deviator stress ratio exceeds 1.0.