Project Object to Surface/Volume Calcs.

[Rainman1]

Please see attachment (object viewer capture). The top surface is my OG, the bottom surface is the bottom of excavation for a building. I want to project the perimeter of the building footprint up to the OG surface at a 1:5 slope. I remember in LDD the perimeter of a building, berm, dam, ditch...could be projected to the OG with specific slopes and then you could create a surface with the projected lines and do a volume calc. between the two. Does anyone know the procedure to do this in AutoCAD Civil 3D 2012?? Thanks in advance.

[john.mckenzie]

Make the building outline a feature line and assign it elevation. use the grading tools to create an infill inside the feature line and create a grading object that slopes to surface. Pick the OG surface as the target surface. This exercise is quite similar to many of the tutorial exercises provided for grading that are included with the software.

After you have graded the building outline to the surface you can use volume tools to get the volume between 2 surfaces, or you can create a volumetric surface and pick the 2 surfaces to compare.

[john.mckenzie]

So, being lazy I did not look at your PDF.

You are almost home.

You do not really need to project to the OG. You will get a volume only where the 2 surfaces occuppy the same horizontal space.

Create a TIN Volume surface. Give it a name, pick OG as base surface and BLDG as compare surface.

Check the stats after the TIN Volume surface builds and voila. Volumes.

this will give a volume as if a vertical wall exists around the building footprint. Any other volume solution requiring a slope WILL require a grading object as mentioned above.

[Rainman1]

Thanks for the info.. I have went through the steps and created my second surface with the grading tools. If you look at the attachment you will see in the first screen capture (in plan) where my building footprint has been projected to the OG surface (red points). In the second screen capture you can see the .2:1 slopes projecting from building footing (elevation 254.75) to OG. The footing elevation is 254.75 and the lowest elevation of my OG surface is 256.2. My building footprint is 440 square metres. Therefore my volume should be at least 650 cubic metres. 256.2-254.75=1.45m 1.45mx440=638 cubic metres. The problem is, when I do a volume calc. between both surfaces it is saying there is only 165 cu. m.???? I don't see a bottom on my building footprint in the second screen capture....could this be the problem????? Thank you.

[john.mckenzie]

move your cursor around over the tinn volume surface. It will report a positive value for eolevation where there is fill and a negative vaqlue where there is cut. If it reports no value for the tin surface, it means that surface does not exist at that location.

if you are not getting values within your footprint, then you do not have a surface there. use the infill function within the grading tools to accomplish this and rebuild the tin volume surface.

Almost there.

[Rainman1]

Yes, I was missing the step where you add the infill. Thank you.