Defining initial stress state for a multilayer model

1

Dear community,

I am trying to define the initial stress state (including Sv, Shmin and SHmax) for a multilayer model. In my case, the overburden is not a problem because it is automatically calculated from gravity and the material properties. However, defining the horizontal stresses remains a challenge.

So far, it only worked when I applied the stresses on the sides of my model as Neumann boundary conditions (as I have the stress gradients). This approach works, but I then have to simulate several hundred years to reach the desired initial stress state. It gives the correct results, but it is not very convenient.

I noticed that there is an <initial_stress> function, but as far as I managed to use it, it works for only one stress component.

Is there a way to define an initial stress state separately in the x- and y-directions, so that I can directly assign Shmin and SHmax without long transient simulations?

Any guidance or examples would be greatly appreciated!

Thank you in advance,
2ophie

2

Hi 2ophie,

actually, all stress components can be prescribed in <initial_stress>. One example is from A2.prj:

        <parameter>
            <name>sigma0</name>
            <type>Function</type>
            <expression>-10e6 + 0.6 * 4e6</expression>
            <expression>-10e6 + 0.6 * 4e6</expression>
            <expression>-12e6 + 0.6 * 4e6</expression>
            <expression>0</expression>
            <expression>0</expression>
            <expression>0</expression>
        </parameter>

You can use, e.g. x, y, z in the expressions.

I hope that’s what you are looking for.

Best regards,
Christoph

3

Dear Chleh!

Thank you for the fast reply and information, this is exactly what I was looking for. I overlooked this example. It also works for my case!

Kind regards,
Sophie