Retaining walls in grading surface

[jimormsbee]

I'm designing a building pad on a fairly steep slope. The property regulations are quite restrictive. All slopes are 2 to 1. The best design I've come up with so far incorporates 3 retaining walls. One below the pad retains 1 to 5 feet of fill. Two above the pad are stepped and support cuts of 2 to 6 feet. I've tried using both feature lines and breaklines with only moderate success. I've searched this forum extensively and have tried many of the suggestions. I've used Civil 3D a number of times for the design of building pads but never using retaining walls. I'm currently using Civil 3D 2014. Any suggestions would be greatly appreciated.

[odoshi]

Your final surface will have to be a combination of the Existing Ground, the Building Pad, and Feature Lines that make up the top of wall (front and back) and bottom of wall.

You can create a combined surface using the Edit Surface > Paste command to combine all of this data.

There really isn't a once size fits all solution. In some cases, you may have to skip the grading object and work strictly with feature lines.

Just remember that you cannot have true vertical faces in your surface. So walls will have to have some offset outard from top of wall to bottom of wall.

Regards,

Mike

[doni49]

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@jimormsbee wrote:
I'm designing a building pad on a fairly steep slope. The property regulations are quite restrictive. All slopes are 2 to 1. The best design I've come up with so far incorporates 3 retaining walls. One below the pad retains 1 to 5 feet of fill. Two above the pad are stepped and support cuts of 2 to 6 feet. I've tried using both feature lines and breaklines with only moderate success. I've searched this forum extensively and have tried many of the suggestions. I've used Civil 3D a number of times for the design of building pads but never using retaining walls. I'm currently using Civil 3D 2014. Any suggestions would be greatly appreciated.

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Take a look at the attached dwg for an example.  I started with an EG surface.  Then where I wanted my first wall, I drew a line and used "Create Featureline from Object" to create a featureline.  I let it get it's elevations from the EG surface so that I know it follows the terrain.  Then I copied the FL toward the back of the wall 0.1 horizontally and used the elevation editor to raise the elevation by 2 ft.  I did this because C3D doesn't like completely vertical surfaces.  Now I have a wall that's 2 ft high.  Then I copied both of the featurelines again.  I used the elevation editor again to raise BOTH of them by 5 ft.  Now I have a second wall that's 5 ft higher than the first.  Then I did it one more time so that I have a 3rd wall 5ft higher than the second.

I didn't take the time to tie them all back in like you would in real life but I think you can see how simple it would be to create retaining walls.

[MikeEvansUK]

Don, you could simplify this (assuming that the wall height is tapering from one end to the other or is a constant height).

Create the Retaining wall lower ground interface level. Add as featureline. Look at the Breakline type there you will find a "Wall type" simply state the offset side then either the height throughout or the height by control points.

As for using grading groups I would personally use an Offset & relative elevation to generate the wall as this will generate a surface from the grading and enable the model to be more dynamic. Note this means they will be ropey too.