Dear all, I am a Ph.D. student at Kharazmi University. Recently I have been trying to simulate a triaxial compression test using the hypoplasticity model for clay using ABAQUS. The UMAT subroutine is provided by Pro Masin on this website (umat_hcea.for).

Figure 1 shows the parameters that I set in the model based on the article “PLAXIS implementation of HYPOPLASTICITY
including standalone ABAQUS umat subroutines by David Masin, I’m using the Brno clay properties as it is described in the paper

Figure 2 shows the model detail (Loads) that it is used in the experiment

as I have simulated the experiment successfully and expected the results to match the triaxial shear test performed on the Brno clay demonstrated in the paper “Clay hypoplasticity with explicitly defined asymptotic states” witch happens in (p = 280kPa), the result clearly doesn’t match as shown in figure 3 and 4

Note that the model size doesn’t have a significant effect on the results as I have tested it multiple times already

Could you please tell me what is the possible reason for this problem?

1qweqwe-2.jpg 1-1.jpg Capture55-0.PNG

3 Comments
  1. Mahdieh Masoudi Author
    Mahdieh Masoudi 4 months ago

    Figure 1 couldn’t be uploaded for some reason so here is the user material parameters
    1 22
    2 1000
    3 0.128
    4 0.015
    5 1.51
    6 0.33
    7 1.35
    8 0
    9 0
    10 0
    11 0.0001
    12 0.2
    13 0.8
    14 5300
    15 0.5
    16 0.5
    17 10000000
    18 2
    19 1
    20 0
    21 0
    22 0
    23 0
    24 0
    25 0
    26 0
    27 0
    28 0
    29 0

  2. David Mašín
    David Mašín 4 months ago

    Hi Mahdie, it seems to me you have intergranular strain active (Ag=parameter 14=5300in your case). But in that paper you refer to the basic varsion of the model, without intergranular strain concept, has been used.
    It also seems to me that you use Pascals as stress units, but the parameters of the model (in particular the value of N) are not stress unit independent, the values in the paper refer to kPa. David

    • Mahdieh Masoudi Author
      Mahdieh Masoudi 4 months ago

      Dear Prof.Mašín, I’ve made sure that my forces(Loads) are declared as kPa and also deactivated intergranular strain (by setting the values of prameters 11 – 16 to 0).
      if the properties of Brno clay in the table4.3 in ‘PLAXIS implementation of HYPOPLASTICITY
      including standalone ABAQUS umat subroutines by David Masin ” are declared as kPa, the new results still don’t match the experimental results shown in the paper described

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