Undrained dynamic behaviors of saturated clays under compressive stress paths considering cyclic confining pressure

The dynamic properties of saturated soils are dependent on the stress paths. More and more test results based on cyclic triaxial tests with cyclic confining pressure show that the stress paths with cyclic confining pressure have great influences on the deformation and resilient characteristics of granular materials such as sands. In this study, the cyclic triaxial tests with cyclic confining pressure are employed to study the coupling effects of cyclic deviatoric stress and cyclic confining pressure on the dynamic behaviors of saturated clays, which simulate the coupling effects of cyclic axial normal stresses and cyclic lateral normal stresses in real traffic loading. The test results show that: under undrained conditions, in comparison with the results in conventional cyclic triaxial tests with a constant confining pressure, the cyclic confining pressure influences greatly the development of the excess pore water pressure, reduces the accumulation rates of the permanent axial stain and increases the resilient strain (i.e., decreases the resilient modulus); and with the increasing ratio of the amplitude of cyclic confining pressure to the amplitude of cyclic deviatoric stress, the decrease of the permanent axial strain and the increase of the resilient strain are getting larger. Two prediction models of permanent settlement and resilient modulus considering the cyclic confining pressure are proposed.