[GeoMechanicsApplication] Add documentation for hardening in Mohr-Coulomb in the form of markdown #13993

mnabideltares · 2025-11-24T15:25:26Z

📝 Description
Add documentation that explains the purpose, setup, and expected results of the unit tests for the Mohr–Coulomb hardening/softening implementation. This ensures reproducibility, helps new developers understand the test suite, and makes it easier to verify correctness.

🆕 Changelog

Extended Readme.md

WPK4FEM

Dear Mohamed,
Thank you for the large effort of putting this documentation properly in markdown. Still I have quite some remarks. Adding the picture of the zones that we have used before would be very helpful.
Regards, Wijtze Pieter

applications/GeoMechanicsApplication/custom_constitutive/README.md

WPK4FEM · 2025-11-25T13:48:40Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+Note: These formulations will be extended for more physics-based form.
+
+
+#### Iterative process


A flow diagram is probably faster to understand than writing this in words.

Thank you for the diagram. I have a couple of remarks about it:
1 using a bent curve look not common to me, please use straight lines and corners.
2 the shape that encompasses "Map trial stresses" is used for choices. Around "Map trial stresses" I would expect a rectangular box.
3 the shape that encompasses "Map trial stresses" I do expect around the convergence criterion that decides whether you are ready or should loop.

Further:

the lambda probably is lambda dot

"update plastic strain" the action is more "calculate plastic strain increment"

in the preceding text we should mention that kappa is the state variable. in this case its content is an equivalent plastic strain. That is a more commonly used description than hardening variable.

material parameters are phi_0, psi_0 and c_0, H_phi, H_psi and H_c. Here the state variable dependent parametersare updated.

WPK4FEM

Hi Mohamed,
Thank you for the work, writing documentation is a tedious thing. In the issue, it also mentions documentation for unit tests. That I would remove, the unit tests should be self-documenting. The work here documents the implementation.

Reading again I realize that previous time I should have opened another view. Looking at just the rendering gave a way easier readable document. Now I have a lot more comments, but I hope they are easy to answer.

Regards, Wijtze Pieter

applications/GeoMechanicsApplication/custom_constitutive/README.md

deltaresmf

Hi Mohammed, I think most of my comments are text-based and the organisation of the document. Hopefully you can make use of the comments

deltaresmf · 2025-12-05T13:30:47Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

@@ -1,63 +1,72 @@
 # Constitutive laws




Suggestion: Overview of the content

Linear elastic
1.1 Introduction
1.2 Implementation

Mohr coulomb
2.1 Introduction (Criterions, when applicable, why)
2.2 Implementation Mohr-Coulomb with tension cut-off
2.3 Implementation Mohr-Coulomb with hardening/softening

deltaresmf · 2025-12-05T13:36:00Z

applications/GeoMechanicsApplication/custom_constitutive/README.md


-## Mohr-Coulomb with tensile cutoff
+## Mohr-Coulomb with tension cutoff



I would suggest to add an introduction to the Mohr-Coulomb model using the figure.

I would add the following description from which you can derive the function below

'''math
\tau_f = c+\sigma'sin{\phi}
'''

Maybe also good to list the tension cut-off criterion here F_tc and the flow function and give a list of symbols with what they mean and their units.

It might also be good to state what the state can be:
'''math
F_{mc}=<0 elastic behavior
F_{mc}>0 plastic behavior
'''
Do we have a condition for F_mc= 0 when it is on the critical state line?

deltaresmf · 2025-12-05T13:39:59Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+  - In the case of regular failure zone, then it is mapped back to the Mohr-Coulomb yield surface along the normal direction of flow function. The flow function is defined by

 ```math
    G(\sigma) = \frac{\sigma_1 - \sigma_3}{2} + \frac{\sigma_1 + \sigma_3}{2} \sin⁡{\psi}


Suggested change

G(\sigma) = \frac{\sigma_1 - \sigma_3}{2} + \frac{\sigma_1 + \sigma_3}{2} \sin⁡{\psi}

G_{MC}(\sigma) = \frac{\sigma_1 - \sigma_3}{2} + \frac{\sigma_1 + \sigma_3}{2} \sin⁡{\psi}

deltaresmf · 2025-12-05T13:58:51Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

 # Constitutive laws


 ## Incremental linear elastic interface law


Linear Elastic model

Do we only have a description for the linear elastic behavior of the interface elements or linear elastic behavior in general, I would add a description of the linear behavior for elements

deltaresmf · 2025-12-05T14:00:04Z

applications/GeoMechanicsApplication/custom_constitutive/README.md



-## Mohr-Coulomb with tensile cutoff
+## Mohr-Coulomb with tension cutoff


Suggested change

## Mohr-Coulomb with tension cutoff

## 2. Mohr-Coulomb with tension cutoff

deltaresmf · 2025-12-23T15:46:43Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+
+Then
+```math
+    g = (\tau - \tau_{corner}) - \frac{1}{\sin{\psi}} (\sigma - \sigma_{corner}) = 0


Where does the g come from?

deltaresmf · 2025-12-23T15:48:43Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+    \dot{\lambda} = \frac{c \cos{\phi} - \sigma^{trial} \sin{\phi} - \tau^{trial}}{\sin(\psi) \sin(\phi) + 1}
+```
+
+Then update the principal stresses based on the mapped values. They updated principal stresses need to be rotated back to the element axes system.


Suggested change

Then update the principal stresses based on the mapped values. They updated principal stresses need to be rotated back to the element axes system.

Then update the principal stresses based on the mapped values. The updated principal stresses need to be rotated back to the element axes system.

deltaresmf · 2025-12-23T15:50:44Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+Then update the principal stresses based on the mapped values. They updated principal stresses need to be rotated back to the element axes system.
+
+### Rotation matrix
+The rotation matrix is derived from the eigenvectors of the Cauchy stresses. Having three eigenvectors related to the principal stresses


I think it is important that this is explained a bit more

deltaresmf · 2025-12-23T15:56:36Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+    \boldsymbol{m_{dev}} = \boldsymbol{m} - \bar{m} \boldsymbol{I}
+```
+
+Then


Suggested change

Then

Then the .. is calculated:

deltaresmf · 2025-12-23T15:59:08Z

applications/GeoMechanicsApplication/custom_constitutive/README.md

+```

-For detailed formulations, see [here](documentation_data/Mohr-Coulomb-with-tension_cutoff-formulations.pdf)
+Where $\epsilon$ is a tolerance.


Is it wise to use epsilon as a tolerance?

Added documentation in the form of markdown

0e3aafa

mnabideltares self-assigned this Nov 24, 2025

mnabideltares requested a review from a team as a code owner November 24, 2025 15:25

mnabideltares linked an issue Nov 24, 2025 that may be closed by this pull request

[GeoMechanicsApplication] Add documentation for hardening in Mohr-Coulomb #13846

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mnabideltares added 5 commits November 24, 2025 16:42

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avdg81 requested a review from deltaresmf December 4, 2025 10:47

Deleted the pdf document, as it is replaced by markdown

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[GeoMechanicsApplication] Add documentation on how to apply hardening in Mohr-Coulomb #13828

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		Note: These formulations will be extended for more physics-based form.


		#### Iterative process


		## Mohr-Coulomb with tensile cutoff
		## Mohr-Coulomb with tension cutoff

	G(\sigma) = \frac{\sigma_1 - \sigma_3}{2} + \frac{\sigma_1 + \sigma_3}{2} \sin⁡{\psi}
	G_{MC}(\sigma) = \frac{\sigma_1 - \sigma_3}{2} + \frac{\sigma_1 + \sigma_3}{2} \sin⁡{\psi}

		# Constitutive laws


		## Incremental linear elastic interface law

	## Mohr-Coulomb with tension cutoff
	## 2. Mohr-Coulomb with tension cutoff

	Then update the principal stresses based on the mapped values. They updated principal stresses need to be rotated back to the element axes system.
	Then update the principal stresses based on the mapped values. The updated principal stresses need to be rotated back to the element axes system.

[GeoMechanicsApplication] Add documentation for hardening in Mohr-Coulomb in the form of markdown #13993

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[GeoMechanicsApplication] Add documentation for hardening in Mohr-Coulomb in the form of markdown #13993

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