Elastoplastic analysis of cyclic torsion stress-strain responses of soft clays

The undrained cyclic triaxial compression tests and the undrained cyclic torsional tests without static axial deviatoric stress of soft clay are conducted to analyze whether the elasto-plastic model developed by the authors can describe the stress-strain response of soil elements with general stress state. The stress-strain responses associated with two stress states are obtained from tests. Model parameters are determined from cyclic triaxial compression test results. The stress-strain responses of soil elements associated with cyclic torsional tests are predicted by the model, and the predictions and test results are compared. Comparisons show that the predicted torsional shear stress-strain loops of soil elements without static axial deviatoric stress are less than test ones, but the predicted and test variations are consistent. The predicted variations of cyclic torsional accumulative shear strains with the number of cycles are consistent with test results. Researches show that the incremental elasto-plastic model can describe undrained stress-stain responses, especially the cyclic cumulative strain response of soil elements with the general stress state.