Effects of principal stress rotation and cyclic confining pressure on behavior of soft clay with different frequencies

Soft clay is subjected to complex cyclic stress paths involving a combination of cyclic vertical and horizontal stress with principal stress rotation caused by traffic load. In this study, three groups of tests, namely tests with principal stress rotation, cyclic confining pressure, and combination of principal stress rotation and confining pressure, were conducted at different load frequencies using Wenzhou soft clay with hollow cylinder apparatus to investigate the undrained cyclic behavior of soft clay. The development of pore water pressure, accumulative strain, axial stress–strain relationship, and resilient modulus were analyzed. Experimental results show that the different stress paths play important roles in the cyclic behavior. The principal stress rotation accelerates the degradation of the resilient modulus due to the accumulation of axial strain. The cyclic confining pressure constrains the development of axial strain, which results in a larger resilient modulus. A lower load frequency results in a larger pore water pressure, accumulative strain, and degradation of resilient modulus. These results provide reference for the assessment of settlement induced by traffic load on soft soils. •Three groups of cyclic (1000 cycles) torsional shear tests are carried out for different stress path caused by traffic load.•Deformation behavior is significantly dependent on cyclic shear stress and confining pressure.•Both principal stress rotation and cyclic confining pressure have an obvious influence on resilient modulus.•Load frequency has a significant effect on the relationship of axial stress-strain and resilient modulus for all the three stress paths.