Hello, I want to use the hypoplastic model for granular materials downloaded from https://soilmodels.com/download/plaxis-umat-hypoplas-zip. The UMAT file umat.for is the model for sand. I followed the instruction https://web.natur.cuni.cz/uhigug/masin/plaxumat/node5.html. I have some questions about the initial state variables and the model itself:
(1) The initial state variables should be assigned in the input file, but I found it can work if I did not. Are there any problems? I found the StVarIni.for, which includes a loop to assign the parameters 17-22 to the initial state variables 1-6? Does this file is necessary?
(2) I found the parameters of the model are seemed highly related to void ratios. I want to use in dynamic analysis, how can I calibrate the parameter hs (I think this one is related to shear modulus) by G0? And I found the pressure-dependency is considered by the parameter n. If I assign n=1, the model is pressure-independent? and the ground is homogeneous?
Any comments or suggestions are highly appreciated.

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2 Comments
  1. David Mašín
    David Mašín 5 days ago

    Hi,
    (1) you can initialise void ratio through parameter 16, but not intergranular strain. So if you do not need intergranular strain, or if it is enough for you that it is initialised to 0, you do not need stvar.ini
    (2) as for this question, please study “Mašín, D. (2015) Part 4: Determination of material parameters, PhD course “Hypoplasticity for Practical Applications” handouts [Presentation]” from https://soilmodels.com/publications/
    Regards David

    • Yusheng Yang Author
      Yusheng Yang 5 days ago

      Hello, David
      Thanks for your reply. I want to consider the intergranular strain, I will try the stvar.ini.

      Best regards, Yusheng

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