[GeoMechanicsApplication] Add intersection between compression cap yield surface and Coulomb yield surface

[mnabideltares]

📝 Description
The cap yield surface and the Coulomb yield surface intersect. In order to determine the mapping zone, the intersection point of the cap and Coulomb yield surfaces must be identified.

This formulation is required in terms of the stress invariants 𝑝–𝑞, rather than the 𝜎–𝜏 representation. Therefore, the Coulomb yield surface must first be expressed in 𝑝–𝑞 space.

The procedure is as follows:

1. Derive the Coulomb yield surface in 𝑝–𝑞 form (already provided in the documentation).
2. Obtain an analytical solution for the intersection point between the Coulomb and cap yield surfaces.
3. Implement the analytical solution in the numerical code.
4. Defining two new regions related to the cap.
5. Add unit tests.
6. Documentation

🆕 Changelog

• Added detection for two new regions, namely cap return zone and cap corner region
• Added mapping for these new regions
• Added unit tests

[avdg81]

Hi Mohamed,
Thank you very much for preparing the integration of the compression cap into the Coulomb model. Since there are still two failing unit tests, this PR probably needs a bit more work, but what you've made so far is a very nice starting point. 👍
I have several suggestions for you, all quite minor things. I also have several questions, which are probably the result of my lack of understanding. I would appreciate it very much if you could help me understand better how the compression cap works. Thanks.