Visco-hypoplastic modelling of cyclic behaviour of saturated clays

The present work develops a novel visco-hypoplastic model to account for both time and cyclic effects of saturated clays. The model has three new features: (1) A new strain term that combines the hypoplastic flow rule and strain rate is integrated into the visco-hypoplastic framework, allowing for the accurate simulation of residual strain accumulation upon cyclic loading. (2) The intergranular strain concept is further incorporated into the developed mode to reproduce the stiffness increase due to reversal loading. (3) Inherently anisotropic clays typically exhibit an asymmetric strain accumulation between the triaxial compression and extension sides when subjected to cyclic loading, for which we introduce a state variable into the stiffness function of the model and transform its hypoelastic stiffness matrix into a transversal one. These improvements enable the model to effectively simulate the strain and pore water pressure accumulation of saturated clays under cyclic loading. To validate the proposed model, undrained and drained triaxial tests with different cyclic loading paths on three different clays are simulated. All comparisons demonstrate that the model is capable of capturing cyclic stress–strain–time behaviours of saturated clays.