PLAXIS 3D Tunnel crossing with volume elements

Hi all,

First question here :) For a project I'm working on I am modelling a set of access tunnels used to allow construction of an underground structure (in PLX 3D 22.02). Starting out from an initial 2D project which works well I tried extending the geometry to 3D using the built-in converter.

2D situation

Unfortunately, at the crossing of the tunnel and the two supporting walls there is a narrow triangular overlap which cannot be meshed with any level of refinement I've tried so far.

2D-3D conversion

As an alternative I've tried manually re-drawing the geometry and intersecting/reclustering/snapping shapes to avoid the overlap altogether. This has not resolved the meshing issue.

Manual re-draw

Are there any known issues with intersecting volumes generated by the tunnel designer and regular volumes? Do you have any advice on how to proceed with this?

Kind regards,

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  • Dear Ivaylo,

    Welcome to the community! Nice project you have there.

    Probably PLAXIS 3D finds it more difficult to handle the sharp angle of the supporting walls that intersects with the tunnel. 2D geometries tend to always be simpler to deal with.

    The first question back is, do you need this level of detail in your model? Do you need this sharp angle or by simplifying the geometry there by avoiding the sharp angle and "glue" it in a more rough way, it would still yield the same response?

    In modelling it is common to simplify geometries while still getting the geotechnical results we want to have.

    The second question is about the geometry itself and how it will be in reality. Do you believe that during construction that sharp angle of the two inclined walls will be respected? That is something to consider when you simplify how you create your geometry.

    In a more generic way, I would definitely first confirm the area that causes the problem, so by removing this part of geometry does the model work fine? I trust that it should. So, then your focus would be on how to adjust the geometry to achieve a good quality element distribution (result in Output > Mesh).

    If you need more assistance with this project, please submit a service request. Then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport

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  • Dear Ivaylo,

    Welcome to the community! Nice project you have there.

    Probably PLAXIS 3D finds it more difficult to handle the sharp angle of the supporting walls that intersects with the tunnel. 2D geometries tend to always be simpler to deal with.

    The first question back is, do you need this level of detail in your model? Do you need this sharp angle or by simplifying the geometry there by avoiding the sharp angle and "glue" it in a more rough way, it would still yield the same response?

    In modelling it is common to simplify geometries while still getting the geotechnical results we want to have.

    The second question is about the geometry itself and how it will be in reality. Do you believe that during construction that sharp angle of the two inclined walls will be respected? That is something to consider when you simplify how you create your geometry.

    In a more generic way, I would definitely first confirm the area that causes the problem, so by removing this part of geometry does the model work fine? I trust that it should. So, then your focus would be on how to adjust the geometry to achieve a good quality element distribution (result in Output > Mesh).

    If you need more assistance with this project, please submit a service request. Then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport

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