[GeoMechanicsApplication] Fix Zero-Diagonal error in the a thermal case

[mnabideltares]

The user has issue with a thermal case.
Makes the mesh by Gmsh. For a mesh, it works fine, but changing the mesh, it leads to Zero Diagonal error.

Success.zip
Fail.zip

[mnabideltares]

                "SPECIFIC_HEAT_CAPACITY_SOLID": 0.0,
                "SPECIFIC_HEAT_CAPACITY_WATER": 0.0,
                "THERMAL_CONDUCTIVITY_SOLID_XX": 0.0,
                "THERMAL_CONDUCTIVITY_SOLID_YY": 0.0,
                "THERMAL_CONDUCTIVITY_SOLID_XY": 0.0,
                "THERMAL_CONDUCTIVITY_WATER": 0.0,
                "SOLID_COMPRESSIBILITY": 1.0,

The material parameters for stage 1 are wrong.
In the working case, somehow it works but giving non-physical results.
I the failing case, it shows the problem, because setting all those coefficients as zeros, it leads to zero storage and diffusion matrices. The mesh here is correct, the problem is not from the new mesh.

[mnabideltares]

Hi Tom,

The issue is not related to the mesh—the new mesh is correct.

The root cause lies in the initial stage. In the material parameters defined for this stage, both the heat capacities and thermal conductivities are set to zero. As a result, the storage and conductivity matrices are entirely zero (including their diagonals), which leads the solver to flag an invalid input due to zero matrices.

With the old mesh, the solver did not raise this error, but this does not imply the results were valid. In fact, the initial stage likely produced non-physical results under those conditions.

Additionally, there is an issue with the tables: they all start at time zero, whereas the initial stage begins at -600. Although this mismatch has not yet caused the simulation to fail, it is a critical inconsistency that should be addressed.

Regards,
Mohamed Nabi