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[GeomechanicsApplication] Add documentation for compression cap#14348

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geo/14332-documentation-compression-cap
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[GeomechanicsApplication] Add documentation for compression cap#14348
mnabideltares wants to merge 4 commits intomasterfrom
geo/14332-documentation-compression-cap

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📝 Description

The formulations for the compression cap and its intersection with Coulomb yield surface, and return mappping need to be documented.

🆕 Changelog

  • Extended the documentation for the compression cap to include its intersection with Coulomb yield surface, the cap regions, and the return mapping.

@mnabideltares mnabideltares requested a review from a team as a code owner April 2, 2026 14:50
@mnabideltares mnabideltares self-assigned this Apr 2, 2026
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@WPK4FEM WPK4FEM left a comment

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Hi Mohamed,
Please find my comments.
Wijtze Pieter

Comment on lines +104 to +125
```math
A = 1 + b_1 a_2^2
```
```math
B = -2 b_1 a_2 c_2
```
```math
C = b_1 c_2^2 - c_1
```

```math
b_1 = 1 / X^2
```
```math
c_1 = p_c^2
```
```math
a_2 = \frac{6 \sin{\phi}}{3 - \sin{\phi}}
```
```math
c_2 = \frac{6 c \cos{\phi}}{3 - \sin{\phi}}
```
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The many intermediate variable definitions are more a programming aid than making it more readable for me.

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I tried to show how the second order polynomian equation was derived, to be able to follow the process if it will be necessary in the future. So, I tried to include the intermediate process. What do you think about it?

Comment thread applications/GeoMechanicsApplication/custom_constitutive/README_cap.md Outdated
Comment thread applications/GeoMechanicsApplication/custom_constitutive/README_cap.md Outdated
Comment on lines +255 to +261
We define the following vectors,
```math
\Delta \sigma = \left[\sigma_1 - \sigma_2 \; , \; \sigma_2 - \sigma_3 \; , \; \sigma_3 - \sigma_1 \right]^T
```
```math
\Delta \sigma^{cor} = \left[\sigma_1^{cor} - \sigma_2^{cor} \; , \; \sigma_2^{cor} - \sigma_3^{cor} \; , \; \sigma_3^{cor} - \sigma_1^{cor} \right]^T
```
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Naming these differences "Delta" is confusing for me. In return mapping the Delta sigma is usually a stress increment.

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What do you suggest for naming?

Comment thread applications/GeoMechanicsApplication/custom_constitutive/README_cap.md Outdated
```

### Return mapping from cap corner zone
The cap compression zone is the rigion where the trial principal stresses are,
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Suggested change
The cap compression zone is the rigion where the trial principal stresses are,
The cap compression zone is the region where the trial (p, q) stress invariants are demarcated by the following two lines,

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Done

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I still find "rigion" on that line.

Comment thread applications/GeoMechanicsApplication/custom_constitutive/README_cap.md Outdated
Comment thread applications/GeoMechanicsApplication/custom_constitutive/README_cap.md Outdated
Subsituting the stresses with the mapped stresses, we get the following relations.

```math
A = \frac{\Delta \sigma^{cor} \cdot \Delta \sigma^{cor}}{2 X^2} + \frac{1}{9} \left( \sum_{i=1}^3{\sigma_i^{cor}} \right)^2
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Then \sum sigma_i / 3 looks like p^{cor}, but that would lead to a confusing mix of principal stresses and p,q stress invariants.

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\sigma^{cor} is defined beforehand, in line 265.
However, if you think it is still confusing, what do you suggest?

@mnabideltares mnabideltares requested a review from WPK4FEM April 13, 2026 07:25
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[GeomechanicsApplication] Add documentation for compression cap

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