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.