Access Road design

[Anonymous]

I wanted to know if the software can create a line at a certain slope along an existing surface from a known start and end point.

Thank you very much for your time.

Jerry Padgett

[Jeew-m]

Dear Friend,

Yes you can.

First create an alignment where your slope line need to placed.

https://www.youtube.com/watch?v=0_R6jT3k9Ec

Then create the surface profile to get the existing ground profile.

https://www.youtube.com/watch?v=1PAv4aiQ_xY

Then create the design profile at the stations and grades you wish.

https://www.youtube.com/watch?v=EM6w2izGteM

Thanks

[civilman1957]

You can also use a feature line.

Go to the "feature line" pulldown in the Create Design menu, choose Create Feature line. It will ask you for a starting point and then an elevation. Click on your starting point. It asks for the endpoint, and you choose that, and then an elevation. If you want to create the line to match a given surface at the beginning and end points, choose the "surface" option when it asks you for the beginning and then the end elevations.

[dbinkney]

I think we need more detail.

Are you trying to determine what the slope is given the elevation start/end points?  Or are you trying to create a slope based on a specific grade/%age?  i.e., are you evaluating or designing?

[Anonymous]

First off, thank you very much for taking the time to reply. Here's my situation:


We are designing a site for a pump storage facility (dam) in Virginia (in the mountains) so the existing ground is undulating to put it mildly.
I have a known start point at the crest of a dam and need to design the centerline of an access road to the lower reservoir crest (also known location/elevation) with no cut/fill along the centerline of this road. So I wanted to know if the software can draw a line along the surface at a given max slope, with minimum radial turns. Afterwards, I offset this line 25' to each side and grade the cut/fill from the edges of the road.



Can this be done? I can't help but think it can. I can manually do it, and have with the other shorter roads, but I'm trying to save as much time as possible.

Thank you again.

J

[dbinkney]

Thanks for the details, sounds interesting! 

There are a lot of smart folks on here, but I would do this manually as you were thinking.  Draw a pline down the alignment, convert to a feature line on that ex. conditions surface and then manually review the slopes in the elevation editor:

https://knowledge.autodesk.com/support/civil-3d/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Civi...

You could also create a small surface from that feature line (offset to the sides) and use the slope evaluation tool to find where you need make adjustments.

Hope this helps, I am going to keep an eye on this to see if someone can offer an automatic method.  Good luck.

[ChrisRS]

Make a reference surface at the required slope them use the MINIMUMDISTANCEBETWEENSURFACES function to trace the intersection between the reference surface and the existing surface.

One way to create a reference surface:

Create a tin surface named "reference"

• Draw a feature line from the base point to the crest point.
• Create a stepped offset on either side of the line wide enough to enclose your anticipat5ed path. Use an elevation difference of 0.
• Add the two outside feature lines to the "reference" surface.
• Type MINIMUMDISTACNEBETWEENSURFACES and select the "reference" and "existing grade" surfaces.

Your desired path should be created as a static 3D polyline. This path will have a PI at the location of each tin line of either surface that it crosses. You may want to weed it.

The following video uses a different method to make a reference surface, but does illustrate the procedure. 

Delineating the Intersection Between Two Civil 3D Surfaces 

[Anonymous]

Yes, there certainly are some very smart folks on the forum. I've seen a few different approaches to my issue, but none that do what I was hoping it would. I actually find it hard to believe there isn't an option for this. If you plug in a few criteria (eg, min radius for bends, Max/Min Slope %, which surface to use, etc), and the software would draw the line over the surface to the specs. But noooooo.



Thank you very much for taking the time to reply. I really appreciate it.

Jerry