Surface Creation Help

[Anonymous]

Hello, 

I have the task of creating a bottom of excavation surface and it is quite a challenge due to the elevations of the site. The footprint of my surface has an elevation change on 50 ft from one side to the other and I need to have my final surface have a 3 percent slope. 

Above is the design surface where i have retrieved my footprint from. I have been instructed that the bottom of excavation surface should look similar to this but with 3 percent slopes instead of 3:1. How would I achieve this? I have tried many different things. Highest elevation on the footprint is 1200' which occurs on the north side of the footprint and the low point is about 1150 which occurs on the southeast of the footprint. 

Let me know if you need more info. 

[rl_jackson]

Assuming your background surface is a C3D surface, you can create a Featureline out of the Top of excavation line, and have that resulting Featureline take on the elevation of your existing surface. From there you can use a grading to to create the bottom of your excavation at a 3:1 slope and create a surface from the resulting grading to paste to your exisitng surface to get a final surface.

[Anonymous]

I think i misspoke, but yes the Existing Ground is a C3D surface. I am not sure what you mean by Top of Excavation Line. The footprint on my surface is set to take elevations from existing ground. The existing ground has significant elevation changes on all sides and I need to obtain a smooth 3% slope not 3:1. Attached is the result of adding the footprint to a surface as a breakline. I need this smoothly sloping at a 3% grade.

[Anonymous · Accepted solution]

will a 3% slope work in the footprint? that is, will the existing ground allow it? It looks steeper than that to me, but I do not know the horizontal scale of the image.

If you are going, roughly, from the farthest Northwest boundary to the farthest Southeast boundary you could add breaklines in across this space. Then on the sides create grading objects that target that breakline derived surface. then the surface will be primarily the footprint plus the target or intersection line from the grading objects.

But there are corners to account for, etc. it isn't going to be easy. You'll get a lot of ugliness to clean up with breaklines.

another alternative is to make all but a strip around the edge at 3%, nice and flat. then use the strip as a "buffer - create a feature line around the footprint and target the flat surface on the interior. The slope from the edges to the 3% flat area will be whatever it will be - in other words it will vary according to the existing ground at the footprint.

No matter what it is going to be messy. Use grading objects, and breaklines to force it to do what you want best as you can.

[Anonymous]

Yes I am finding 3 percent will not work probably. I am using grading groups and breaklines to try and manipulate it how I want, which is the question of how to do it easiest. Thank you for your input. It is very messy!