FE-Implementation of Elasto-Plastic Model for Granular Materials and Analysis of Foundations

The non-associated plasticity model
is utilized to simulate a three dimensional nonlinear finite
element analysis on sand. The model is a three-dimensional
generalization of the Cam-Clay model with yield- and flow potential
functions expressed in a common format, but with different shapes
and hardening rule depending on both the shear and volumetric
stains, which enables modelling of dilation. The model has been
implemented as a user-defined mechanical material behavior in
ABAQUS finite element code using an implicit integration algorithm
with explicit update of the hardening parameter. The implemented
subroutine UMAT in ABAQUS is verified by carrying out a triaxial
test on single element and comparing the result to the experimental
data and implementation in the high level language MATLAB. The
implemented subroutine is used to study the influence of the
rigidity of the footing. Simulation with both absolute rigid and
absolute flexible footings are carried out and the deformation
behaviour, the differences in vertical and contact stress
distributions beneath the footing are presented. In addition the
effects of using large strains are investigated by simulating a
flexible strip footing resting on sand and comparing the
deformation behaviour to the small strain solution.}