Unwanted water load appear in sectional face when the ground surface formed by importing

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Tue, 21 Jul 2020 07:37:12 GMT

Dear Stefanos,

Great thanks for the information about intersect BoreholeVolume_1 ... Polygon_2 command.
I did not think about this simple way.

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Stefanos Papavasileiou — Tue, 21 Jul 2020 06:37:21 GMT

Dear William,

The problem you experienced can happen due to a small inaccuracy of the created geometry (usually from import).

Most of the times this inaccuracy is too small to be noticed while checking the model, however, the program will indicate this when applying the default fixities.

By default all lateral (and bottom) boundaries have fixities. The default fixities are applied to the extremes of the model, i.e. Xmin, Ymin, Xmax, Ymax, Zmin, which means that if one of the lateral boundaries, as correctly mentioned by Rushan, is not perfectly vertical, then some part of the geometry will not have any fixities as the whole lateral boundary is not the extreme of that model, but probably some part of the geometry.

As a result, when fixities are not applied and a water level is present, external water loads are applied to the model, which are not supposed to be generated at all.

In that case, you need to inspect the part of the geometry that is missing the fixities and show external water loads and go back to Input and try to fix it.

One way is to check the importance file and fix the issue before importing it to PLAXIS.

Another way is to force an intersection between a vertical surface you can quickly create in Input and the soil volumes. The intersect command can be executed in the command line as follows:

intersect BoreholeVolume_1 Polygon_2 # for two objects

intersect BoreholeVolume_1 BoreholeVolume_2 BoreholeVolume_3 Polygon_1 # for multiple objects

As a result, the manual intersection will create new objects which will be editable in Structures mode. Then, you can delete the parts that seem to "stick out" to fix the geometry. Typically you can check the command response to identify all created objects from intersections.

If you encounter any similar issues you cannot fix, please submit a service request.

Then, one of our support engineers can help you in detail: https://apps.bentley.com/srmanager/ProductSupport

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Wed, 15 Jul 2020 20:28:59 GMT

Dear William,

Great! I am very glad, that your issue has been resolved.
You are welcome ;)

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

William Lau — Wed, 15 Jul 2020 20:12:00 GMT

Dear Rushan,

Thank you for your big help! I found the way out! It really depends on the boundary of the imported DXF surface.

I imported the top soil layer by "structure" and buildup solid/volume, and "connect" to another soil layer, it works and it gives me a clear cut boundary!! Until now it works great. Thank you x 1000!

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Wed, 15 Jul 2020 18:31:56 GMT

Dear Wiliam,

Unfortunately, I do not know the way for triming the soil body.

In your project I see two possible ways:

1. Check the origin surface in DXF, Import settings in PLAXIS and Contour in Project properties window on Model tab.
2. Check plate geometry via echo command to get the exact coordinates of plate elements. Another method: delete all structures and check the error only with soil body. If the problem remains, the trouble is in the imported geometry.

Sorry, but it is very difficult to help without origin 3D project.

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

William Lau — Wed, 15 Jul 2020 15:48:06 GMT

Oh!!! I got it, but this error boundary is the soil body.

I can apply the dummy surface approach to trim the "structures", but can I do this for the soil body?

I checked the imported surface, it seems correct, but I do believe there are error coordinate that as you said (0.0001m).

What should I do to trim the soil body?

Really thanks to your big help!

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Wed, 15 Jul 2020 15:44:31 GMT

Dear William,

As you can see, some geometry on the xmin boundary is out of contour:

Green arrows (fixed geometry) means, that plate geometry and the geometry between plates are out of of xmin coordinate.

Please, check x-coordinate of plate elements. It should be the same as xmin coordinate.

Also you can use approach with dummy surface and intersecting the geometry. For this you need to create vertical surface with x-coordinate = xmin, intersect it with plates and delete extra geometry out of model contour.

Hope it will help.

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Wed, 15 Jul 2020 15:40:42 GMT

Dear William,

As you can see, not whole boundary has fixities, only some parts:

It means, that all geometry that have green arrows on this error boundary has the different x-coordinates in comparison to the x-coordinate of boundary. Please, check it. Also you can try the approach with dummy surface for intersecting and deleting extra geometry: create surface with x-coordinate equals x-coordinate of xmin boundary, intersect it with plates and delete extra geometry.

I hope it will help.

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

William Lau — Wed, 15 Jul 2020 15:30:45 GMT

Dear Rushan,

Thank you for your reply!

After the review, here's the 2 result for checking the "Fixities", and they are different!

but I don't know the actual meanings...

Can you give me any advise? Thank you.

RE: Unwanted water load appear in sectional face when the ground surface formed by importing

Rushan Gizzatullin — Wed, 15 Jul 2020 15:17:31 GMT

Dear William,

Such results are common for the models, where one of the vertical boundaries is not «strongly» vertical (or horizontal, if we speak about zmin).

It can be connected to imported geometry, because PLAXIS is very sensitive to all coordinates. In DXF you may not see it, but in the reality there are some point with coordinates, for example, 0.000001 m. In such cases we need to check all coordinates. In Output you can switch on Fixities (Ctrl + F) to see, is everything all right on all boundaries. In your case first of all we should inspect the xmin boundary.

In some cases I create vertical dummy surface (bigger that vertical boundary) via extrude option and intersect it with volumes and other geometry:

Then I delete all geometry out of model contour.

Also it is interesting whether do you have an error (waterloads on the boundary) on Initial phase with Gravity loading calculation type and only soil geometry.

I hope this information can direct you to the right solution.
Good luck!