Non-coaxial Behaviour of Clay Subjected to Cyclic Simple Shear Loading

Non-coaxiality refers to the non-coincidence of the principal stress direction and the principal plastic strain rate. In order to quantitatively investigate the non-coaxial behaviour of clay under cyclic loading, undrained cyclic simple shear tests are conducted on the red clay collected in Heilongtan. The Multi-directional Dynamic Cyclic Simple Shear (MDDCSS) was used to implement this experiment. Both monotonic and cyclic simple shearing are applied to the sample and the corresponding soil behaviours are analysed. Parametric analysis in terms of different moisture content and initial stresses are systematically performed. Conclusions can be drawn that the principal stress direction is advantageous to the principal plastic strain increment direction at the initial stage of shearing, and gradually coincide with the shear progression. In addition, the degree of non-coaxiality gradually reduces with an increase in the stress ratio. These results can provide an experimental basis for constitutive modelling under the principal stress rotation.