Problem description

The Concrete model is an advanced constitutive model, particularly developed to simulate the time-dependent response of shotcrete and concrete within the elasto-plasticity framework. Among other features of the constitutive model, it includes a visco-elastic law to account for creep deformations.

When using PLAXIS 3D 2018.01 (and preceding versions), it has been observed that the constitutive model is not exhibiting any creep deformations. Therefore, this aspect cannot be currently modelled with the Concrete model in PLAXIS 3D.
This is now solved in PLAXIS 3D CONNECT Edition V20.

Note that this issue has been only identified in PLAXIS 3D, not in PLAXIS 2D. When performing a PLAXIS 2D analysis, creep behaviour can be modelled by using the Concrete model.

Solution

This issue is now solved in PLAXIS 3D CONNECT Edition V20

For usage in older versions, note that PLAXIS has implemented more constitutive models to model time-dependent behaviour (i.e. creep and relaxation).

One of such models is the visco-elastic perfectly plastic model, where a maximum of 4 Kelvin-Voigt elements (i.e. a spring and a dashpot connected in parallel) are used to simulate isotropic visco-elastic behaviour, while the onset of perfect plasticity is defined by the Mohr-Coulomb failure criterion. This constitutive model has been implemented as a user-defined model.
Alternatively, for soft soil, the Soft Soil Creep model can be used to account for its time-dependent response.