Building a complicated DTM, and I can't seem to come up with a good method to do this, wondering what others do.
At an intersection where one road has a 4:1 fill slope, and the other one has a 2:1 fill slope. Slope transitions from one to the other in the radius. Fill is high enough that the slopes intersect before they hit the ground. Where is the toe of slope?
Same situation except in a deep cut. Where is the top of slope?
I use Terramodel and it does it quite easily a couple of ways depending on how you have it set up (in road templates or just slopes).
I assume the 4:1 is the "main road"
and the 2:1 is the "side road."
Lets say for discussion the main road is running north/south, side road east/west.
At the point of the PC of the flair from the mainroad into the "side road" I'd begin a side slope transition from 4:1 -> 2:1 and have the full steepness of the 2:1 at the PT of the flair.
so, in effect, the daylight catchpoint will slowly creep in towards the side road throughout the turn in the flair.
I'm trying to imagine how I'd do it in Civil, but i'll need to think on it for a bit.
So, to answer your question... I'd do it in Civil3D but let the corridor handle it, I wouldn't try to control it too much.
I use InRoads, which also does this easily. Is for proposed DTM? In design we would use intercept slope. Or done in templates.
The way I used to do it was create multiple surfaces. Then you can manage them yourself. But I am very far from an expert on this, I just looked for some kind of "work around".
Sometimes the software isn't as smart as the user. Just IMHO.
I have had to do some custom modeling to design rock quarries. I would project surfaces from 3D Polylines (hinges). Then manually trim and create break lines and model from that. In Carlson you can use the design pad template to find the intersections. But I think they also handle modeling multiple roads at an intersection by using their road network routine, so there would be no manual editing of the DTM.
Yeah, thats what I do. Maybe I can explain better.
This is exaggerated but say you have a 50' radius to the edge of pavement with a 10' shoulder on the mainline. If the fill is 25', where the radius starts on the mainline with the 4:1 the toe will be 110' from the edge of pavement, or 60' behind the radius point. Assuming the existing ground is level and the cut is the same on the side road with the 2:1, which has a 4' shoulder, the toe will be 54' from the edge of pavement, or 4' behind the radius point from that direction. I also use Terramodel, but the transition from the 4:1 to the 3:1 creates a meandering line that loops around behind the radius point and crosses itself. In the reaL world the slopes will intersect somewhere along the slope, with a break in the slope. I haven't been able to make the software figure it out though.
OK, how bout this:
don't grade inside the flair using the templates.
Tell the 2:1 on the side road to start at the station which is adjacent to the 4:1 toe daylight of the flair PC. (I'm envisioning a 90 degree intersection)
Then manually lay in a handful of feature lines (3D POlys) to fill in the DTM in the flair.
