Dear community
I have 4 Question in implementation of Hypo-sand Umat in ABAQUS could someone kindly explain?

1. I checked the Umat file from ( and i understand this subroutine needs 15 parameters that these parameters are listed in the first picture but when i searched in and found one question from mr. Akshay Sakhare that modeled triaxial test in ABAQUS with Hypo-Sand
and he sent the parameters that he used in user material that you can see in the second picture that I attached in the following
what is the definition of 16th parameter
when I delete this parameter my abaqus send an error and the job terminated
2. if I want to impliment the basic hypo-sand wich parameters have to be equal zero? as you know Parameters of the intergranular strain concept for sandy soils are 9th-14th (listed in the first picture)
3. my third question is that why we use bulk modulus of water in the hypoplastic constitutive law?
is it for saturation conditions?
4. and when in was reading ( I found that we have 14 state variable and I entered the amount of Depvar equal 14 but in the UMAT file I cant find state v more than 13 (may be my mistake) (third picture)
is it correct that we should enter the Depvar equal 14?

01-0.JPG 02-1.jpg 03-2.JPG

1 Comment
  1. David Mašín
    David Mašín 1 year ago

    Dear Sobhan, please check better the documentation. As you can read here:, par16 is initial value of void ratio, then obviously your simulation crashes when you delete it. As you can read clearly on the very same page, if you want to switch off intergranular strain, mR should be set to zero. It is also written there that statev14 is not used, this is why you cannot find it in the code. Bulk modulus of water Kw is there if you want to simulate fully undrained response – so-called penalty approach is used there, where Kw is added to stiffness matrix to produce (almost) constant volume conditions.

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