Numerical implementation of a constitutive model for soil creep

Abstract

We discuss the numerical implementation of a creep constitutive model to facilitate the modeling of longterm soil creep. Multidimensional soil creep models are generalized from the one-dimensional soil creep model proposed by Bjerrum in 1967, which was based on field test data and was later modified for transient loading conditions by Vermeer et al. in 1998. Here this differential form of one-dimensional creep model is extended to two- and three-dimensional states of stress and strain by incorporating concepts from viscoplasticity. The devised multidimensional creep model takes into account both volumetric and deviatoric creep strain, with creep deformation of the soil defined by several material parameters. The model is incorporated as a plane strain element subroutine in a nonlinear, time-incrementing finite element program, along with iterative corrections within each time step. Numerical analyses are conducted to demonstrate soil creep by using published experimental data. The verified computer code will be a useful research tool for estimating settlements in structures founded on soils exhibiting creep.