A finite element solution scheme for an elastic–viscoplastic soil model

A Newton–Raphson solution scheme with a stress point algorithm is presented for the implementation of an elastic–viscoplastic soil model in a finite element program. Viscoplastic strain rates are calculated using the stress and volumetric states of the soil. Sub-increments of time are defined for each iterative calculation of elastic–viscoplastic stress changes so that their sum adds up to the time increment for the load step. This carefully defined ‘iterative time’ ensures that the correct amount of viscoplastic straining is accumulated over the applied load step. The algorithms and assumptions required to implement the solution scheme are provided. Verification of the solution scheme is achieved by using it to analyze typical boundary value problems.