Creating a subgrade surface

[Anonymous]

Im sure this topic has been brought up multiple times. I cannot be the only designer trying to accomplish this with the least amount of headache.

My office is contemplating moving to Civil 3D (from Carlson) a lot in part for Dynamic 3D Surface creation and for Storm Sewer Networks and Hydrographs built in. I will need to be able to create accurate subgrade (both buliding and pavement sections) surface models for use with both earthwork calculations and exporting this surface for construction machine control. The machine control portion of this need will require this final subgrade surface to be a SINGLE surface.

My question to you fine people is... Has anyone found a more productive way to accomplish this other than the methods spelled out in thie post from 2 years ago now?

http://forums.autodesk.com/t5/autocad-civil-3d-general/surface-manipulation/m-p/3780139/highlight/tr...

I look forward to all of the experience i have seen on this forum and what I can learn from you all.

Thank you...

[troma]

I didn't just read all of the 63 posts in that conversation, so I'm not sure of what is covered. (I probably did read it two years ago.)

But I see that Eric Chappell's Blog was referenced in post 8;
http://ericchappell.blogspot.co.uk/2012/01/magical-way-to-calculate-volumes.html

That's probably the best approach I know of.

[redtransitconsultants]

Calculating volumes is one thing - but creating the actual subgrade surface for say control points for construction is completely different. It's a common problem across all the industry in the software but probably more so in the Landfill industry as we have various thicknesses of surfaces to define liners with the landfill.

Civil 3D has the Raise/Lower option on surfaces, but yes, it only effects the Z value, whereas an excavation surface would actually be larger in 2D area than the final grade surface. The steeper the slopes, the farther your elevations are off for your subgrade surface.

I've seen numerous ways of developing the subgrade surfaces, but there is no real simple one click way to do it. I have logged a feature request with Autodesk for a Surface Offset command - which would help get us closer to the result we need.

[Anonymous]

That is correct Steve. I need to be able to export this subgrade surface for machine control. I could have done the volume adjustments by hand if that were not the case...

[neilyj666]

...and the landfill layer thicknesses are invevitably perpendicular to the surface rather than a simple vertical level difference.

[neilyj666]

The total net volume adjustments are indeed fairly simple to do by hand but if you need to split up the project into various phases/operational areas to get the "real" cut and fill it becomes a bit trickier - in this case the Dynamic differential tin method is the way to go.

Corridor modelling will get the subgrade surface easily but not all projects lend themselves to corridors.

This is why Civil 3D is so well suited for BIM....not...;)

[Anonymous]

What is this Dynamic differential tin method you speak of?

[Joe-Bouza]

It is a method for creating stratum(s) that would be dynamic to change in you model

>>>HERE<<<<

[troma]

Nice document.
Just to be clear, the method is the same as Eric Chappell's blog post referenced earlier. Though it looks like this document is the original, by Creg Dieziger. Eric Chappell gives credit to Creg Dieziger in the blog post.

[Joe-Bouza]

I believe so

there is a process description in that document that confuses me, I can recall it but will get back to you with a question

[OliverE]

Hi @Joe-Bouza and @troma thanks for posting the DDTS document. I tried following it to create a subgrade surface after already creating my  Proposed Finished Ground Level surface (P-GL) as described in Scenario 2 of the document. I'm hoping you can provide some clarification on Step 2 and 3 of Scenario 2 for me.

Step 2 we create feature lines and set them to the material depth. Note 2 says to offset adjoining lines by 0.01 units. When we do this do we need to have another feature line in between the two offset feature lines and set it to an elevation of 0? If I don't do this, each individual material depth surface that I create in Step 3, Option 1, is just a group of feature lines all at the same elevation, ie. a 2 dimensional plane. Or does this get taken care of when I paste each depth surface into the overall depth surface? 

I have attached a dwg with all my depth surfaces in it. If I use the Proposed Subgrade Depth (PR-Subgrade_depth) surface as the base surface in my composite surface comparing to my P-GL (data referenced from my design drawing), then paste the composite surface into an empty TIN surface as described in Step 4 and 5, my resulting Proposed Subgrade Ground Level (P-SGL) surface looks like the attached screenshot with gaps appearing at the interface of each material. I can only guess this is due to adding the extra feature line at an elevation of 0?

Any help would be greatly appreciated. 

Cheers,

Oliver

Windows 10, C3D18

[OliverE]

Update: I tried again without the 0 elevation feature line and it seemed to work fine once I had paste all my individual surfaces into the overall depth surface. One thing I did notice was the order of pasting didn't work in the way the document explains it. It seemed like if you added a surface that had a show boundary in an area that was a hide boundary for one of the other surfaces, the hide boundary would override the show boundary if the surface with the hide boundary was added second.

[troma]

You don't want to go to zero elevation between your different depths.
If you could create a perfectly vertical step from one material depth to the next material depth adjacent, this would be best. But TIN surfaces can't cope with vertical steps, so we use a very small offset to make it as close to a vertical step as possible.

[OliverE]

Hi Troma,

Yes, without the 0 elevation it worked fine. However, using relative feature lines seems like a much simpler process to get the same result. Was the DTTS method what people used before relative feature lines were got released?

Thanks,

Ollie