Nonlinear Elastic-Perfectly Plastic Model of Soil and its Numerical Implementation and Application

To combine the advantages of the Mohr-Coulomb and the Duncan-Chang models, a new model called the nonlinear elastic-perfectly plastic model was established. In the numerical implementation of this model, a newly developed smoothing technique for yield and plastic potential surfaces was employed to accurately fit the side face of the hexagonal pyramid surface of the Mohr-Coulomb criterion. A user material subroutine was developed in Abaqus and was verified by modeling a conventional triaxial test of a soil specimen with the feature of a nonlinear elastic-perfectly plastic model. Finally, to further validate the applicability of this model and its subroutine, the 3D numerical simulation of a relatively complex deep excavation project was performed, and the results were compared with measured data, the results determined by the method recommended in the current code, and the results of the Mohr-Coulomb and Duncan-Chang models. The comparison demonstrates that the results of this new model were the closest to the measurements.