One section does not compute volume

[tcorey]

See the screenshot. Any ideas what would cause Civil 3D to ignore a single section view among 216 section views when computing volumes?

Thanks!

Tim

[Jeff_M]

It looks like the FG is intersecting the EG, but if there is just the smallest gap I think it gets ignored. So, near the offset 8 location, do they truly intersect? If so, I have no idea what else would cause that.

[joantopo · Accepted solution]

Yes, this is a typical issue in Civil 3d.

I recommend this workaround:

-create a new surface and paste the EG  surface and then add the operation: rise elevation = +0.001 (1mm)

And use this new surface to compute not the original EG surface.

The trouble is sometimes Civil 3d doesn't consider an intersection if a section point is just on another surface section.

I think is a problem of decimals in the coordinates internally in CIVIL 3d to consider if it is really an intersection point with 2 surface sections. 

[tcorey]

Awesome. Thanks.

[joantopo]

Look at the picture.

Your corridor surface section(red) has 2 end section points.

The end point on the right side is obviously quite on the EG surface but the left side, it seems that there is a properly intersection with the EG surface.

if we rise the EG surface, then it is really found an intersection point on the left side.

Another possibility instead of using this workaround (rising a new EG surface), could be create custom subassemblies about slopes with a new input parameter(double) called "extend slope".

So, in SAC, once you have found the intersection point with EG surface, you extend the slope with Delta Y=0.0001

This way, the corridor surface has a extended slope (specially in fill scenarios). It would be the same if you lower the corridor surface instead of rise the new EG surface.

Perhaps, all subassemblies should have this new input parameter = extend slope (with delta Y=0.0001) after the intersection with the target surface.

So, generally, this happens with the toe of slopes from corridor surfaces.

In the top of slopes from corridor surfaces there is no problem.. I think

Regards.

[joantopo]

Summarize:

You have 2 EG surfaces (one of them with rise elevation).

-The original EG surface is used as a surface target in your corridor.

-The another one is used to compute materials.

I don´t like to have to create a new copy of a suface, so another possibility is custom subassemblies (about slopes) with a boolean input parameter called extended slope (delta Y= -0.0001) if they are in fill.