Numerical modelling of visco-plastic soft soils

In many cases geotechnical calculations are made with linear or non-linear elastoplastic
soil models. The most common case in which these types of soil models are not
sophisticated enough is during the modelling of creep of soft soils. Most constitutive soil models
modelling creep are based on volumic strain reduction over time. In this paper the creep is
modelled through shear stress reduction (the viscous behaviour). The key point of viscous
modelling is that this type of stress reduction (Mohr-circle squeezing) also takes place below the
Coulomb failure line. In other words, viscosity is a sort of slow and rate-depending plasticity
without reaching the Coulomb criterion; therefore also the word visco-plasticity can be used. This paper shows that visco-plastic modelling of soft soils will produce more realistic results and shows how this visco-plastic modelling works.