Fix grading issues in corners

[jgjDXYZW]

Hello

I'm using gradings to design a pond, I'm using a slope of 5:1 and a depth of 1 m for this specific pond. However I keep getting issues with the corners, and I've tried to create the pond with different (rounder or less round corners) styles. I've also tried different Tesselation settings. 

How would you go about getting a good surface when grading like this? Is there a checkmark I'm missing (fairly new to Civil 3D) or is there something that can be added to the surface/grading to fix this?

[Anonymous]

A polyline could be sketched following the bottom of pond, and then rounded corners could be added to the polyline, then swap out this polyline for the grading and voila smoother surface.  Oh, also try to limit the vertices around the top of pond using weed command on the feature line.

Also, rule of thumb when we want a consistent slope of 1:5 the top of pond radius at corners has to be larger than the distance to the bottom of pond.  Hope these help.

[Joe-Bouza · Accepted solution]

My preference is to grade from the bottom up.

the grading is telling you there is a geometric issue with your outline. The prescribed depth and slope simply do not work under some of the geometric constraints provided; check it.do a segment by hand and you will have the intersecting slopes on paper as well.

Smooth curvature  is your friend with projection gradings

[samir_rezk]

Hi @jgjDXYZW 

In the Grading Criteria. double check the Interior Corner Overlap is set to Use Average Slope. 

Hope this helps,

[jgjDXYZW]

Appreciate the responses!

@Anonymous It is set to average as the default, so it shouldn't be that. 

@Joe-Bouza Often in the projects I'm giving to work with, I usually have the outer boundary and not the ponds bottom area. So how would you go about a workflow like this? In the attached picture in the first post, I have a very varied existing elevation, that needs to graded down to a known elevation at 1:5. So how can you grade from bottom up in this case? Perhaps grade downwards first and the find where the bottom approximately is and then delete the first grading and replace it with something grading from the bottom up? Or in more regular ponds offset the outer lines until they are where your bottom is supposed to be and then grade upwards instead? What would you do? 🙂

@Anonymous Nice tips, especially about the radius makes good sense that it has to larger. 

[Udo_Huebner]

In such cases, rather than grading 1:5 in one step, it may be helpful to start with 1:5 and offset 5 and repeat this several times to close the overlapping corners. Finally, grade the resulting bottom feature line to the desired depth.

[cwr-pae]

Look at @Joe-Bouza 's 2nd comment where he recommends checking the integrity of the feature line. I create gradings such as you show frequently. Any issues I have similar to yours come from the feature line having doubled or crossing segments.

If you can upload the drawing, I'm sure some one will look at it and give you some hints or out right instructions to repair it. 

[Joe-Bouza]

if the top is etched in stone. I would offset slightly inside a slope, the finesse the radii of the offset line>>> add projection to bottom elevation>>> infill between the two top lines

[Joe-Bouza]

Another reason I suggest grading from the bottom up is the size of the bottom needs to be big enough for maintenance and of course construction vehicles.  If that has been established with the top line provided then it is a non issue