Illegal geometry handling

Hey there,

Basically 2 questions.

  1. Is it possible to run large-strain off in the in-situ stress initialization and then switch to large-strain on when excavating? I thought so, but I was looking at the results of my model, and the mesh isn’t distorted at all so I suppose it’s not possible.

2)When I run my model with large-strain on from the in-situ stress initialization stage, I get the error “illegal geometry in zone xxxxx”. Immediately after 1 min of cycling, What can I do to prevent this?

Thanks in advance.

1 Like

Yes, you can run large-strain off in the in-situ stress initialization and then switch to large-strain on when excavating.
Also you can "zone geometry-update "command.
Good luck

1 Like

@Felipe, you can turn on/off large strain logic at any stage of your analysis. The problem of having large strain ON during initialization is exactly what you are getting: if there are large deformations from gravitational / in situ stress loading, you will start your analysis with potentially highly deformed zones, which may quickly cause geometry error. So you need to think first, is large strain mode really needed and physical in the initialization? Are there initial failures that are physically meaningful at this stage?

Typically, only stresses are of interest during the initialization process, and displacements and velocities are reset to 0 after the initialization. However, if you have badly deformed zones at this stage, they will continue with this shape even as displacements will be reset to 0.

When you turn on large strain, the zones may not necessarily deform so much that it will produce visibly deformed mesh. So I don’t see anything wrong with this, but it of course depends on the details of the analysis.

3 Likes