SANISAND Abaqus UMAT and Plaxis implementations

Description: Abaqus UMAT and Plaxis implementations of SANISAND constitutive model by Dafalias and Manzari (2004).

Authors: Original implementation by M. Martinelli, C. Miriano and C. Tamagnini. Updated version of umat together with Plaxis interface programmed by D. Mašín. The updated version has been developed under the support of Zhejiang University, Hangzhou, China. Special thanks to Prof. Lizhong Wang and to a. Prof. Yi Hong for releasing the implementation to SoilModels users.


  • Dafalias, Y. F. and Manzari, M. T. (2004). Simple plasticity sand model accounting for fabric change effects. Journal of Engineering Mechanics, Volume 130, No. 6, 622-634.

Associated Software and Constitutive Models

  1. Win Mar Soe
    Win Mar Soe 1 year ago

    Hi, where can I read more details about sanisand model and what is the procedure to use in plaxis?

    • David Mašín Author
      David Mašín 1 year ago

      Hi, please re-download the package, now you will find pdf files with information you need. regards David

  2. Krzysztof Sternik
    Krzysztof Sternik 1 year ago

    Hi David, in the file umat-sanisand-readme.pdf it is mentioned that there are two ways of generation of model parameters and state variables: standard and expert. Both involve usage of the subroutine sdvini.f. This file is missing in the package. Could you help?

    • David Mašín Author
      David Mašín 1 year ago

      Hi Krzysztof, sdvini.f is no special, this is standard sdvini which you can get from Abaqus manual. In “standard” mode, you do not need it, you just must properly initialise number of state variables to 36 and set void ratio in Par19. In “expert” mode you need to understand what exactly each state variable means and initialise it accordingly in sdvini.f. But I do not think this is really needed, standard mode should be fine for most applications.

  3. Krzysztof Sternik
    Krzysztof Sternik 1 year ago

    Thank you!

  4. Reza Foroughi
    Reza Foroughi 1 month ago

    Hi David, can i use this model with plaxis v8?

    • David Mašín Author
      David Mašín 1 month ago

      I do not think so. V8 had some different standards, you would have to update it yourself for the old version and compile it again.

  5. Reza Foroughi
    Reza Foroughi 4 weeks ago

    Hi David, about the file umat-sanisand, is it applicable for axismmetric or 2d manner?

    • David Mašín Author
      David Mašín 4 weeks ago

      It is programmed using full 3D notation, so you can use it for 3D, 2D as well as axisymmetric analyses. As for programming, it is out of scope of this forum, but to be honest you should use most recent Plaxis I think.

  6. Reza Foroughi
    Reza Foroughi 3 weeks ago

    hi David.
    i simulate the bearing capacity of a rectangular shallow foundation with umat.
    but i think it is not work well.
    the p-y curve is similar to odometr behavior.
    can you help me?

    • David Mašín Author
      David Mašín 3 weeks ago

      Dear Reza, I can hardly help you. Please note that the implementation here is provided as-is, without any support, and still requires considerable expertise to use. It might be your error, error in paramneters or initialisations, error in umat, or it even might correct response of the model which does not fit observations. In any case, you should either be able to identify the error or to fix error in umat. If you succeed, please share your results with the others. Regards David

  7. Reza Foroughi
    Reza Foroughi 3 weeks ago

    Dear David, thanks for your answer
    another question; about parameters of soil model, what is the parameter number 18 (Ptmult)?
    which number should i use?

    • David Mašín Author
      David Mašín 3 weeks ago

      This is artificial cohesion to eliminate numerical issues. If your analysis runs smoothly, use 0. Otherwise, you can try some small value (say up to 5 kPa) to stabilise the calculation. Small value will have minor effect on strength while stabilising the simulation. Higher values would already affect material properties and then you would have to know what you are doing. Regards

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