I am making a surface model for an interesting little job that has about 100 of these little turnouts along the edge of the road. They are usually just an extension of the crown grade of 3% but they also follow the centerline profile which can get pretty steep at times. I am trying to create corridor surfaces for several layers of material. Just like in a super elevated section, the width of the subgrade is going to change with the cross slope but in the areas where where turnout is not perpendicular to the centerline the cross slope is a function of the profile and 3%.
I can model this nearly perfectly using an alignment and a custom subassembly (the short lines in the picture). The assembly samples a temp finished grade surface and uses it to calc the proper slope for the subgrade extension to the side slope.
This is sort of a pain with design revisions. I'm wondering how somebody else would handle this or looking for suggestions, probably many better ways than mine.
First of all - wow! I've designed a lot of roads with pullouts and turnouts but I've never seen anyone bother to model the slopes around the edge of a turnout like that.
You say that you've built a custom sub for this. Have you considered doing it with the OOTB subassemblies? I'm fairly certain that it would be possible, and that it could be set up so that the subgrade alwasy parallels the top surface.
Another option would be to edit your custom sub so that it only retrieves the temp surface slope and provides it as output, so that you could use a parameter reference to transfer that value to a ShoulderExtendAll sub.
Whatch for trapping water in those turnouts. I find theoretically, anything under 6.5% longitudinal slope with 3% crossfall will trap water in the downstream side of the turnout. Of course I assumed some dimensions of your turnout.
Thanks for the input. I probably didn't spend enough time looking at the ootb assemblies because I was in a rush and knew I could make it work the other way. I'll take a look because using custom assemblies can be troublesome.
I really would like to get away from making this a two step process.
I'm not familiar with your second method. That will give me something to look into.
That is part of my frustration! Because of that we have had to modify many, if not most of these. Unfortunately we are NOT the designers, but the builders of this job and have to follow the plans as much as possible.
The construction company has asked us to create a surface model for GPS machine control. So as we uncover all of these design flaws need to update the model. I'll probably update it several times throughout this job.
I would like to think that the design engineers didn't have a very good og topo, even though their own cross sections show they didn't meet the required thickness above og. But enough venting, I'm glad to know somebody is thinking about this stuff ahead of time.
I think my issue is that it is taking me longer than I want to update the model.
Can I ask how long the job is and how many hours you have into building the model? Just how many layers are necessary to model? does every layer have different slopes? The construction contractor has the ability to dial the elevation of a model up or down when needed to grade subgrade and gravel from a top surface only model. Unless of course they are not consistently the same.
My first question is, how critical is having the subgrade slope be perfectly parallel to the top surface slope? From your attached drawing and text, it doesn't look like it varies much, and probably not that often, either. If that is the case, I would suggest ignoring that aspect of your work entirely.
My thought is, just draw polylines along the edge of pavement where you have turnouts and target those as width alignments in your main corridor. It would be much faster, you wouldn't need the additionbal assemblies and surfaces, and if you can live with the subgrade being off a little in some areas, then it's Miller time, baby.
The job is a little over 6 miles and consists of one main road and two side roads. If you include entering all of the profile and alignment data, supers, calculating offset targets for those turn outs, creating surfaces, cross sections, and grade reports I think I had a little over 12 hours into making the initial model. 3 to 4 hours to make a change that would typically take 1/2 hour.
Although the slopes are the same we are still required to model two surfaces, finished grade and subgrade. I should point out that machine control is just one part of our contract. It is the reason why I'm trying to make it perfect though.
You are correct, as far as machine control goes I could just give them one surface and tell them to raise and lower it. But for this job I need other things like plan template cross sections, end area reports, spreadsheets with elev. data for all breaklines on all surfaces, etc. I just don't see any other way to get that than to model it all.
I wish I could do that, life would be great and I would be catching grayling on a dry fly.
It really does vary a lot though, When I cut a cross section perpendicular to the centerline of the turnout it would show up and I'm sure the contractor or the state would call us on it.
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