Volume Surface Grading Incorrect

[Anonymous]

Hello All,

I at a loss as to why this simple function is not behaving correctly. I have two surfaces, created as typical, one containing existing contours with correctly assigned elevations and the other containing proposed contours with correctly assigned elevations. However, when I create my Volume TIN Surface, the contours generated seemingly do not relate to the existing topo surface. In fact, they close in on themselves and create a totally unusable surface for comparison.

Again, both surfaces were created normally, by importing pline contours from an AutoCAD file. My proposed contours were snapped to the existing and contain the matching elevation information. This is confirmed when orbiting the surfaces in Civil3D.

Please refer to the images below to view the results I have described.

Has anyone had this problem in the past or have an idea as to what might be causing this malfunction? 

Thank you

[tcorey]

Contours for the volume surface won't necessarily follow existing ground. These contours are based on the difference between existing and finished. A contour at 5' represents the line where your fill is 5'.

Post your drawing and we can take a look so that we can give specifics.

[Anonymous]

tcorey- thank you for taking a look.

I have attached the file.

[tcorey · Accepted solution]

I took a look at your file, compared the elevations of the polylines used for eg and fg. The volume surface is giving the correct results.

Maybe you don't fully understand what volume surface contours are showing you. When you display contours for a TIN volume surface, they represent the depth of cut or fill at that point, the difference in elevation between the base and comparison surfaces. These contours might look nothing like the OG or the FG contours. If you create spot elevation labels on this TIN Volume Surface, they will show depth of cut or fill at that point.

There is one possible gotcha. Your fg polylines go from 9308 directly to 9312. There is no 9310. It won't make much difference if the two elevations are correct, but I thought you should know, in case it's an input error.

[Anonymous]

Thank you Tim for clearing that up. 

I am new to this program and my tutorials did not explain what a Volume Surface and it's contour signatures actually represent.

[wfberry]

Just remember, GOOGLE is your friend and a lot faster than this forum. (sometimes)

Bill

[Anonymous]

Thanks Bill,

Google was not as friendly as I expected. 2 of us had been googling and
trying to figure this issue out with no avail so I am thankful for this
forum- even if I had to wait a few minutes for a reply.

[wfberry]

Please don't shoot the messenger.

I am just trying to help.  Here is how I use Google.

Civil 3D, Volume surface

Bill

[Anonymous]

Bill,

I know, I did not intend to come off as unappreciative. Thanks for your
input.

[tcorey]

Yes, Google is your friend, but we're your friends, too.  😉

Anything you ask here is potentially an answer for someone else. That's a good thing.

Keep posting.