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Thread: Best grading approach?

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    Question Best grading approach?

    I have an existing ground surface (developed from 2-foot contours only). I now want to modify that surface to incorporate a new road with open side ditches, culminating at a cul-de-sac. The primary purpose of this exercise is to analyze surface drainage to assess the need for a retention basin.

    My question is:

    Is the use of grading objects only sufficient, or should I consider developing a corridor for the road and ditches?

    Thanks in advance from a C3D-06 (and AutoCAD) newbie.

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    Default Re: Best grading approach?

    It sounds like your have a fairly simple road section and I would use a corridor for any road design work. It may take longer to set up but will you have to do cross-sections sometime in the future? But hey, I'm a road designer and to me the corridor modeling is easer than trying to use grading objects. I tend to think in cross-section and have designed parking lots using civil design alignments and templates. I find it easer to adjust your design to minimize grading and to balance the earthwork. It also looks better because it has smooth transitions, unlike grading with slopes and spot elevations.

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    Default Re: Best grading approach?

    Thank you, I'll use the corridor approach.

    How do you handle cul-de-sacs? Maybe I should start a new thread...

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    Active Member melanie.santer's Avatar
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    Default Re: Best grading approach?

    Quote Originally Posted by dooly
    I have an existing ground surface (developed from 2-foot contours only). I now want to modify that surface to incorporate a new road with open side ditches, culminating at a cul-de-sac. The primary purpose of this exercise is to analyze surface drainage to assess the need for a retention basin.

    My question is:

    Is the use of grading objects only sufficient, or should I consider developing a corridor for the road and ditches?

    Thanks in advance from a C3D-06 (and AutoCAD) newbie.
    Hi:

    I would use the corridor option for the roadway and ditches, after you are finished with the corridor you can export the corridor surface and then merge the EG and corridor surface together to create one FG surface. One thing that I always do is create a copy of the EG before I merge surfaces, just so I have the original EG in case I need it later.

    Hope this helps

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    Default Re: Best grading approach?

    Hi..I just recently finished a cul-de-sac grading..this was in LDD before I converted to Civil 3d. I'm not sure if the way that I've done it is the best/most efficient (I think it is in LDD, at least), but what I did was to define a roadway template for the radius of the cul-de-sac (1/2 of roadway) and then create an alignment around the perimeter of the cul-de-sac (just an arc from intersecting road edge to intersecting road edge, not a full circle - make sure that it is consistent with your finished ground reference point in your template). Then you basically just sweep the profile around the cul-de-sac and you have all of the grade-to-surface capabilities that you would normally have with corridors/cross-sections. Then I just made a surface from that, pasted into my surface made with the road alignment cross section template (corridor in civil 3d), then added a tin line connecting the center of the cul-de-sac with the crown of the intersecting road. I am fairly sure that this will work in civil 3d too, but I don't know about the ability to attach the finished ground reference point anywhere on the profile in civil 3d as you can in LDD...It may be default at the center (edge in this case) of the template..I'm still pretty new at civil 3d, but it seems to all be based on the same engines. Hope this helps!

    Bill

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    Civil Engineering Moderator MHultgren's Avatar
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    Default Re: Best grading approach?

    The way I build my Cul De Sacs is to draw a circle at the center with a radius of 1' then use that as a grading object and grade to the edge of pavement. repeat for gutter, curb sidewalk etc. then once I have the entire circle built, I create my contours as polylines and join \trim them to the contours created by y roadway surface. After I get all my contours joined I build an overall surface using the PLINEs and points, breaklines and I get a fairly accurate surface, complete with steps for curbs and gutters.
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    Member backwoods's Avatar
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    Default Re: Best grading approach?

    I wouldn't use grading objects at all anymore in civil 3d for road design. Take time to learn to build your assemblies and use your corridors. If you have a simple section, then most likely your assembly required is just a drag and drop from your toolspace.

    Corridors are much easier for culdesacs also. Have one assembly build your curb, sidewalk and ditch.

    Daylighting gets a little getting used to, but it is well worth it. (well, except the fatal errors every once in a while.)

    Greatest thing about this is, if you need to edit later on, it is very, very easy to modify, unlike changing a dozen grading objects.

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    Default Re: Best grading approach?

    In fact, you will find at times that corridors work for grading better than grading does for grading. As far as approach, you need to leverage the dynamic surface environment for grading. It is possible to do very complex grading sites without ever touching the gradining tools in Civil 3D. However, I do use a few of them. You should also attempt to leverage Elevations from Surface command that creates feature lines which are pretty stable, and don't forget to use the Create Points tools by Slope/Grade and Distance or Elevation. You can setup your proposed surface to automatically receive these points as you add them... Pretty Cool!

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