Civil 3D Grading

[SkiGuy]

Does anyone know if there there is a way to grade a fill slope up from a feature line that will intersect a steeper slope? The feature line at the edge of the site is a little above the existing grade and the Grading objects only seem to be capable of grading a fill slope down till it intersects, not up. Please, see the attached sketch of this situation.

[mfernandes]

Well!!!!.... I'll be a...!!!

it never ceases to amaze me on what seem to be an obvious requirements sometimes cannot be done.

I thought I could simply use a negative number for grade, well you cannot, OK how about for slope, no again.

So my only suggestion is to use the alignment, profile and subassembly method. Link slope to surface.

Hopefully some else in this group has a better idea.

[SkiGuy]

Thanks for trying, I'd attempted the same thing.

[lambertb · Accepted solution]

Could you set the grading parameter to allow cut only?

[SkiGuy]

Thanks, That seems to work. There is one section where the feature line goes below the existing grade, in which case I need it to switch to a 4:1 slope cut slope, but thinking I'll just have to do that end as a seperate grading object.

Thanks again.

[Joe-Bouza]

IS the setting you change to "Look" at fill first?

[mfernandes]

great job lambert

I guess there is more than one way to skin a feline

too bad we have to resort to tricking the software, but hey! it works.

maybe the terminology in the grading should be grade up and grade down instead of cut and fill.

and it seems to be that in the grading editor......well somewhat

[SkiGuy]

No, I created a copy of my criteria and changed the projection setting under Grading Method to "cut slope" instead of "cut/fill slope" and set the cut slope to 1%. It the areas where my feature line is above existing ground it seems to project that slope up till it intersects the steeper slope in the existing ground. Apparently cut slopes will always project up and since I'm not giving it an option to switch to a "fill" slope it seems to work.

In a small section where that feature line is actually intersecting and going below the existing surface, and is really in "cut" it still tries to apply the 1% till it daylights which is not what I want (in that section I truely want a 4:1 cut slope) so I will probably just need to use the intial run to mark and break up the feature line based upon whether I'm actually in cut or fill to get what I really need.

Thanks.

[lambertb]

I changed it to cut only, but changing it to cut first may work also.

[Joe-Bouza]

How do you get the cut portion done? I tried adding another grading and it kept asking for a 0 transition length?

[Neilw_05]

Setting the criteria to Cut Only simply stops the fill slope from calculating. It doesn't force the grading to find a solution in the cut direction. What you need to do is change the Search Order criteria to Cut First (see the screen cap by mfernandes above). Also see the help file for how to use that option.

[Neilw_05]

By the way, you can set the "Projection" setting to Cut or Fill (vs Cut/Fill) if you only want to compute solutions in one direction

[SkiGuy]

Used the iniital grading using the cut criteia only at 1%, I was able to see where it changed from the feature line being above existing grade to being below existing (i.e. where the daylight limit came back to the feature line before shooting way out). I marked that point, then deleted that grading and used the marked point to break the feature line into two seperate feature lines and generated seperate gradings for each section.

That way I didn't have to mess with a transition. Since its really going from an infill condition (where the feature line is above grade) to a true cut slope of 4:1 where the feature line goes below the existing surface, you don't need a transition. There is actually a point where the daylight limits comes back to the feature line so it is an instantaneous change (same as anytime you go from a typical fill to cut situation along a feature line).

Hope that helps.