In geotechnical engineering, the viscoelastic lumped parameter models that
are commonly used to describe the stress-strain-time behavior of various viscoelastic
medium are mainly restricted to the application of Maxwell and Kelvin-Voigt
models. Three-parameter viscoelastic model as described earlier is also used at
certain situations. These models are used frequently due to their simplicity and for
the easy determination of their parameters by using simple mathematical or
experimental techniques. However, as discussed in the previous sections, these
models are found unsuitable for proper representation of the time-dependent
behavior of the viscoelastic medium. On the other hand, the use of Burger model is
mostly restricted in the field of rock mechanics. However, a detailed scrutiny about
the evolution of the Burger model as described earlier, reveal that in comparison to
the other models, this model has an immense potential in representing the
deformation phenomena occurring in a viscoelastic subgrade when subjected to a
loading and unloading process. Hence, in spite of the four-parameter Burger model
being a simple model in the viscoelastic theory, this model has been selected as the
best model to represent the rheological behavior of a viscoelastic subgrade. As the
model is comprised of linear springs and dashpots, the applicability of this model
would be limited and would not be able to incorporate nonlinearity or damage.
However, these aspects can be incorporated in the model with ease by considering
nonlinear springs and dashpots instead of linear mechanical elements.