How to Create a Sharp Vertical Break Between Two Lowered Surfaces?

[aszucs1]

Hello everyone,

I'm trying to model stripping topsoil at different depths on a project, and I'm running into an issue with creating a sharp vertical edge between the different sections.

Here is my workflow:

1. I have an existing ground surface (EG).

2. To model the different stripping depths, I created two new surfaces. Let's call them "Stripped_30cm" and "Stripped_40cm".

3. I created "Stripped_30cm" by making a copy of the EG surface and lowering it by 0.30 meters. I then used a boundary to isolate the specific area for this depth.

4. I did the same for "Stripped_40cm", lowering a copy of the EG surface by 0.40 meters and using a boundary to define its area.

5. Individually, these two surfaces look correct.
   
   

   My goal is to create a single, final proposed surface that includes both of these stripped areas. When I create a new final surface and use Paste Surface to add "Stripped_30cm" and then "Stripped_40cm", Civil 3D automatically creates a smooth, sloped transition between them where they meet.

   What I need is a sharp, 10 cm vertical break along the boundary line separating the -30 cm area from the -40 cm area.

[Jeew-m]

Hi,
Civil 3D does not usually support vertical faces.

If your two surfaces are exactly on top of each other it will have this issue.

If you can have a small gap between the surface, It should work I think.

[AdammReilly · Accepted solution]

Because of the way surfaces work in Civil 3D, you can't have vertical faces at all. You'll need to offset your boundaries a very small amount to create a gap between the two surfaces. That will give you a single surface with the two surfaces correctly displayed and it shouldn't be noticable in your output (model/sections).

Also have you taken a look at this AU session from 2019: The Handy Mans Guide to Dynamic Differential TIN Surface by @cregdieziger  

This session talks about doing what you're trying to accomplish and should have some tips for dealing with some of the issues that are inherent to surfaces in Civil 3D