The non-convergence of gravity analysis in two-dimensional tunnel modelis

[[email protected]]

Dear stko
I have built a model of shield tunnel in liquefied soil layer. It does not converge in the first step of gravity analysis. I do not know where the problem is. The following is an introduction to the model

1. First of all, I choose binding constraint for the contact between tunnel and soil: equalDOF (X, Y direction)

2. The left and right boundaries of the soil layer are also bound in the way of equalDOF, (X direction)

3. Fix at the bottom of soil layer (X and Y directions)

4. The degree of freedom of pore pressure at the top of soil layer is fixed

Can you help me?

My gravity analysis cannot converge. I will attach my model below. Can you help me modify it?

[STKO Team]

UP elements cannot be analyzed in static analyses due to how the pore pressure DOF is implemented.
Therefore, if you have to run a "static" analysis, you must do it with a Transient analysis and a large time step so that you don't have inertia effects

[[email protected]]

Thank you stko I have modified my model,

but after the gravity analysis (elastic phase), I open the post-processing module and cannot display my post-processing. What is the reason?
(The post-processing of other models can be displayed normally when I open them)
page 1 is my model post-processing results
Here is my modified model

[[email protected]]

Dear stko
Im sorry
please download this model
The above model was sent incorrectly

[STKO Team]

the top layer of soil is detached from the other one. It is falling down.
Select the 2 soil layer, merge them using the SewFaces command, and re-mesh.

sew.png (97.52 KiB) Viewed 2699 times

The analysis should run after that

[[email protected]]

Thank you very much! i will try again!
and i want to ask a question,
In the phase of gravity elasticity analysis, I used a long analysis step（5step 5000totally time）
In the gravity plastic analysis stage,If I still use the analysis step size of (5 steps, a total time of 5000s), the analysis cannot converge, so I use the analysis step size of (40 steps, a total time of 2s) to calculate the convergence, is this correct?

[STKO Team]

It should be fine. Just record the acceleration and check if they are small enough

[[email protected]]

ok，that is small enough
and i have an another question
if I want to extract the shear strain and shear stress of the soil element in the post processing. In the two-dimensional XY model, what I should extract？is the Gaussian point ε 12 and σ 12？

[STKO Team]

if I want to extract the shear strain and shear stress of the soil element in the post processing. In the two-dimensional XY model, what I should extract？is the Gaussian point ε 12 and σ 12？

yes