I am curious if it is possible to modify only specific portions of a surface? For example, I have recieved an xml surface representing FG for a project, and want to do an earthwork calculation, could I raise and lower only portions of the project say by using specific boundaries for the asphalt paving, concrete etc. and then implement the raise & lower surface feature for these portions of the FG surface.
At this time I have been creating multiple surfaces for each particular feature of the site, then paste the FG surface, add a boudary and lower appropriately. Finally, I have to go through and paste each particular feature and its small surface into one "subgrade surface" to get an accurate representation. This method results in countless small surfaces and alot of leg work for something that seems like it should be simple.
I know that the surface defentions (FL's or corridors), should they be provided, would make this easy, but there have been several occasions where these are not being made availble by the project sponsor.
Not that I know of but the items you refer would be an easy area time depth, no?
It sounds like the method your describing is close, but I would suggest pasting the whole FG into a new SUBGRADE surface AND THEN lower to your subgrade depth and apply your boundaries.
If you need the SUBGRADE surface with the original FG to compare to EG, then you'll have to create one more surface (FG & SUBGRADE) and paste the original FG and then the SUBGRADE.
Don't try to paste the SUBGRADE back into the FG, that creates a circular reference.
I think the technique you are using is the most accurate aside from recreating the model with corridors and gradings.
I can't think of any other techniques that don't require a similar amount of work. C3D's lack of subgrade tools for gradings is one of the reasons I have preferred a competing product up to now.
The problem with area times depth is you have to account for whether the subgrade is in cut or fill. If in cut you'll need to add the subgrade depth to the depth from FG, in fill you'll need to subtract the subgrade depth.Typically the FG is going to have both conditions.
You can create an ISOPACH surface to establish which parts are in cut or fill and then use the appropriate Area x Depth for each region but that can end up being alot of work when you have varying subgrade depths (i.e. under pavement vs. under sidewalks, etc) as well as when the subgrade transitions between cut and fill in numerous places within a feature. Too it is not as accurate since the cut/fill depth becomes variable near the edges where the subgrade transitions from cut to fill.
I'm not seeing the difficulty in the process I mention above.
I do this on a regular basis. I always have subgrade surfaces that have the FG pasted in and boundaries around my various paving, conc. etc. and then lowered to my depth of material.
You don't need multiple surfaces for non-contigous areas. You can control individual areas by having an overall hide boundary followed by multiple show boundaries.
This way it is always dymanic and continually current with any changes that are made to the FG.
In addition, these additional sub-grade surfaces can be shown on profile views with the profile hatches and all be up to date and current with any FG changes.
I use this method to tackle this problem - works well for me...
.....but raises another question: how can Civil 3D be called a BIM tool when it can't do calcualtions such as this easily. Obviously corridors can extract quantities fairly painlessly but not everything needs, or works well with, a corridor
A picture is worth a thousand words. If total earth work is done between FG an EG any proposed volume pavement, sidewalks curbs drainage structures will always increas the total cut on a job. Show me how this math dos not work?
See my response to Neil. Be free to show me the error in the math
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