Hi @sahatsuparng_pip, thanks for letting us know. What you refer to in your last post is caused by the fixed-length links in your assembly (I circle them in the following image).

When the cut/fill conditions are met, your assembly places this geometry, and since the length of the links is considerable, it ends up out of the terrain, making your daylight go down looking for the surface and creating the fill portion you see at the end of the section view

You can solve that problem using any of the following options:
1. Open the section editor. Go to that specific section and edit the geometry of the fixed link to make it fall within the terrain. For example:

In this example, I am located in section 0+005.00. I opened the parameter editor and edited the cut slope from 1.0:1.0 to 0.5:1.0. This edit will be true just for that section, overriding the default values I assigned in the assembly before building the corridor.

2. If you are using Civil 3D 2023.2 or newer, use corridor transitions to edit the geometry of that problematic link for that specific region. If you want to know more about that, visit this link: Model Civil 3D Corridor Transitions Using Any Subassembly
3. Create a custom subassembly with a dynamic dimension for the height/length of that link, so you don't have to worry about it. This can be done with Subassembly Composer.
4. Ideate a better way to arrange conditions or sectorize your corridor so you can place a different subassembly with a lower height/length for that link so the end is within the terrain and the cut slope is correctly generated.
I hope this helps. Best regards!
Camilo Fernández
P.Eng | Transportation
