Not a problem. It's like this since quite a while. Just checked the old V4.12, I still have on my test machine, and it's the same there.
You do need an outer boundary if you want to create a hole in a surface.

Green lines are part of the surface (not added as boundary), blue lines are added as boundaries only.
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Ronny Schneider
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Original Message:
Sent: 11-24-2024 15:11
From: Clem Slatter
Subject: How to split a surface into multiple surfaces
Apologies Ronny, I must have missed your reply.
There must have been a change along the way somewhere that I missed as I wasn't aware you could do this now without the outer boundary.
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Clem Slatter
Original Message:
Sent: 11-24-2024 14:55
From: Ronny Schneider
Subject: How to split a surface into multiple surfaces
The outer boundary is not necessary in this case. That's why I proposed to just add the 12 outlines of the single areas.
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Ronny Schneider
Original Message:
Sent: 11-24-2024 13:50
From: Clem Slatter
Subject: How to split a surface into multiple surfaces
Scott, you can add an outer boundary to your surface, this can be a polygon that encompasses the surface.

Then add individual boundaries to each of the surfaces in the model.

This will still be one single surface but the triangles will be limited to the internal boundaries that you have created.
**Note that I have found instances on imported surfaces where the triangles will still spill out of the boundaries, the fix for this is to retriangulate in TBC.
If you want individual surface for each then I would use command Offset Surface and offset by zero height using a clipping boundary.
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Clem Slatter
Original Message:
Sent: 11-21-2024 08:58
From: Scott Cavendish
Subject: How to split a surface into multiple surfaces
Our designer provided a LandXML surface file for subsoil excavation with all areas in one file. I'm able to import it into TBC, and use the triangle option as per FDOT procedures, but TBC connects all of the areas with triangles to make one giant surface. The trim surface edges tool doesn't work. Explode surface doesn't seem to do anything. I am able to create a boundry around one of the areas, but then the rest of the surface disappears. I've searched all over and can't find a solution on how to break this surface up into multiple surfaces. Any help would be appreciated. The xml is attached if that helps.

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Scott Cavendish
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