Super-subloading surface model with improved state variables in 3D stress space and its numerical implementation

A 3D improved super-subloading surface model is established to discribe the complex behaviors of overconsolidated and structured soil precisely. By comparing with those of the existing super-subloading surface models, the evolution of overconsolidation state variable R and structural state variable R* in this model is ameliorated. Moreover, the realm of the model is expanded to 3D stress space as the shape of yield condition in π plane is assumed to be sleeked by utilizing the failure criterion suggested by Sheng. Then the procedure of implicit stress-update algorithm is introduced, and the model is realized in finite element software by subroutine. Subsquently, the rationalities of the model and the subroutine are verified in a series of numerical simulations. Finally, Boom clay and Fujinomori clay are simulated, and the numercial simulation results are compared with the test data. The comparison shows that the proposed model can describe the characteristics of overconsolidated and structured soil accurately.