Three-dimensional rheological model for double-yield surface based on equivalent time

In order to describe shear contractibility, dilatancy and rheological properties of soils, Yin-Graham’s equivalent time method is used to derive a three-dimensional rheological model for double-yield surface. Firstly, Yin-Graham’s three-dimensional rheological equation is used as the first yield surface rheological equation reflecting the shear-contraction mechanism. Secondly, Matsuoka-Nakai yield criterion is used as the second yield surface reflecting the dilatancy mechanism, viscoplastic work is used as hardening parameter and the non-associated flow rule is adopted, the stress-viscoplastic work-time relationship is proposed using Mesri’s modeling idea, stress-viscoplastic work-viscoplastic work rate relationship is obtained according to the equivalent time method, and the second yield surface three-dimensional rheological equation is established under Perzyna’s over-stress theory. Again, according to the theory of double-yield surface model, a three-dimensional rheological model of double-yield surface is proposed by combining the two rheological equations. The classical fourth-order Rung-Kutta method is used to compile the difference calculation program, and the numerical solution of the rheological model is obtained. Finally, the predictions are compared with the measured values by using triaxial consolidation undrained rheological test data of Canadian bentonite and remoulded Hong Kong marine deposits to verify the applicability of the model in rheological tests. The results show that the model can simulate the development process of multi-stage and single-stage loading in undrained rheological tests, and can reflect dilatancy and shear contractibility of soils.