Adding Breaklines to a Civil 3D Surface

I see a number of Civil 3D users adding a surface smoothing edit to smooth contours. Surface smoothing often creates a very large TIN Surface (Triangulated Irregular Network) and CAD file. A construction contractor may also have a difficult time working with a large TIN and CAD file if used for Machine Control. Breaklines can be added to a surface to create a cleaner TIN and contour lines.

Here are the steps:
Once the breaklines have been modeled and are ready to be added to a surface, adjust the Supplementing Factors in the Add Breaklines dialog box. The following settings work well but adjust them as needed.

• Turn on and set the Distance to 10.00’.
• Set the Mid-ordinate Distance to 0.01’.

Below are the links explaining the Supplementing Factor Distance and Mid-ordinate Distance from Autodesk’s Help file.

Autodesk Civil 3D Help: Supplementing Factors

Autodesk Civil 3D Help: Mid-ordinate Distance


Below are images of a surface with the default settings.

 

 

 

 

Below are images of a surface with the adjusted settings. Additional editing may need to be added to smooth the contours.

 

 

Let me know if you have any questions. 

Creating a Retaining Wall using Civil 3D Feature Lines and Grading Objects

If you need to create a retaining wall due to some sort of limits, I’ll show you how to quickly create a wall with feature lines using the grading objects from the finished grade.

As you can see in the images below, the grading object and contours daylight well into the RPA limits. I would like the retaining wall to be built about 10’ outside of the RPA but maintain the finished grade slope to the top of wall.

• RPA limit is the bold magenta dash line.
• Grading Objects are Green.
• Feature Lines are Red.

 

 

 

Steps:
1.   For this exercise, I already have an existing surface and a proposed surface created using the grading objects and features shown in the above images.
2.   Offset the RPA line 12.2’ outside of the limits to create the inner bottom of wall.
3.   Trim the newly created line where it crosses over the daylight line/grading object.
4.   Offset the line again 2.20’ towards the RPA limits to create the outer bottom of wall.
5.   Click Feature Line from Objects from the Create Design panel then select the inner bottom of wall.
6.   Set the standard Site and Styles and check Assign Elevations.
7.   Click Ok.

8.   Select the Finished Grad surface.
9.   Click Ok.

10.   Create another Feature Line from Objects then select the outer bottom of wall.
11.   Set the standard Site and Styles and check Assign Elevations.
12.   Click Ok

13.   Select the Existing Grad surface.
14.   Click Ok.

15.   Click the Modify tab on the ribbon.
16.   Click Stepped Offset on the Edit Geometry panel.

17.   Type 0.10 for the offset distance.
18.   Select the inner bottom of wall then specify the side to offset the feature line towards the RPA limits.
19.   I’m going to create a 6 inch high lip above the finish grade so type 0.5 an elevation difference.
20.   Click Stepped Offset again.
21.   Type 2.00 for the offset distance to create the top of wall.
22.   Select the newly created top of wall line then specify the side to offset the feature line towards the RPA limits.
23.   Type 0.0 for an elevation difference to form flat top of wall.
24.   Cap the ends of the walls with 3D Polylines or Feature Lines.
25.   Delete the Grading Object within the area of the retaining wall.

 
26.   Add the retaining wall Feature Lines to the Finished Grade surface as Breaklines.

 

 

27.   Adjust the surface boundary limits to the outer bottom of wall.

Below are 3D prospective images of the existing ground retaining wall added the finished grade surface.