Hi, I am a newbie in Plaxis 3D. I am setting the model of deep excavation with lateral support.
First, I creat the soil/existing ground by borehole only, and i set some volume to deactivate since the ground surface is not flat. And I creat all excavation volume by "structure: surface with extrude tool", it is not accurate due to the excavated surface with the different gradient in real case. The result generated is reasonably close.
Then, I found that the existing ground surface can be imported in borehole setting. I imported the surface in DXF format and it looks really great!! After that (re-calculation), it fails just in stage 1 (inserting sheet pile wall without any excavation). I dont know whats going on and i found that there are some external water load adding to the sectional face, which does not appear in my first method.
Please help.... Thank you.
Best Regards,
William
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!
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.
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.
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!
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.
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!
Great! I am very glad, that your issue has been resolved.You are welcome ;)