Automatic Calibration of advanced constitutive soil models

The numgeo Automatic Calibration Tool(set) (numgeo-ACT) aims to simplify and speed up the calibration process and, in particular, to reduce entry hurdles associated with the application of advanced constitutive models such as Hypoplasticity or Sanisand. In addition to simplified calibration, the ACT allows for the investigation of parameter dependencies and reproducibility studies by determining large numbers (several hundreds) of equivalent parameter sets of equal quality for the same material. The ACT is based on heuristic optimization methods and offers access to different similarity measures to quantify the differences between experimental data and simulation results. An overview of covered methods and constitutive models is given below. 

In the following animation, the results of an example calibration of the parameters of a hypoplastic constitutive model for a medium sand are given.

How the parameters change during optimization is shown in the example of the parameters φc (critical friction angle), hs (granular hardness) and the exponent n for the calibration shown above. 

As mentioned at the beginning, ACT offers the possibility to investigate parameter dependencies and reproducibility studies with a large number of different parameter sets. An example of this is shown in the following animation, which shows an extract from a calibration of a hypoplastic material model for the sand used above, repeated 500 times. It should be emphasized here that the fit between experiments and simulations is of comparable quality for all 500 parameter sets – although an impressive scattering of the parameters is observed.


numgeo-ACT is currently not yet freely available, but is planned for the medium term. In the meantime, we are happy to perform the calibration for you using the ACT – free of charge, of course. If you are interested, please contact Jan Machacek (

Further information

  1. Jan Machaček, Patrick Staubach, Carlos Gran-das, Torsten Wichtmann, Hauke Zachert. On the automatic parameter calibration of a hypoplastic soil model. Acta Geotechnica, 2022.
    [BibTeX] [Download PDF]
      title={On the automatic parameter calibration of a hypoplastic soil model},
      author={Machaček, Jan and Staubach, Patrick and Gran-das, Carlos and Wichtmann, Torsten and Zachert, Hauke},
      journal={Acta Geotechnica},
  2. Jan Machaček, Simon Siegel, Patrick Staubach, Hauke Zachert. Automatic Parameter Calibration of Two Advanced Constitutive Models. Challenges and Innovations in Geomechanics, 2023. Springer International Publishing.[]
    [BibTeX] [Download PDF]
      title={Automatic Parameter Calibration of Two Advanced Constitutive Models},
      author={Machaček, Jan and Siegel, Simon and Staubach, Patrick and Zachert, Hauke},
      booktitle={Challenges and Innovations in Geomechanics},
      publisher={Springer International Publishing}