Weighted Cut & Fill

[a.szwyd]

I've been told that Civil 3D can do a weighted calculation when it comes to Cut & Fill analysis but not really sure how to tackle it, basically a case of comparing a finished design DTM with an existing terrain model. With the proposed design model you might have different formation levels eg/Plots set at 600mm below finish level & Rd's set at 450mm below finish, now if the site was made up of a 50-50 split you'd end up with an average of 525mm below the finish design level, obviously their would be additional construction depths than these. So is there a way to add a weighted calc depending on the split of how the site is made up.

[neilyj666]

I think you have been misinformed - you would need to do the computations yourself,

If you have the polyline boundaries of the various areas you can do an offset inside of ,say ,10mm and assign an elevation to each boundary of the construction thickness e.g. 0.6 and 0.45. Also add an external boundary to the whole site with an elevation of 0.

Create a standard TIN surface using these polylines and then create a volume surface with the thickness/depth surface as Base and Final DTM as Comparison.

Copy the volume surface to a new standard TIN surface and you have a formation surface. If the construction make ups change, simply change the elevation of the thickness polylines and the models will dynamically update. 

This technique is the Dynamic Differential TIN and is one I use all the time. 

[a.szwyd]

Ji would you be able to send me an example of one of the Dynamic Differential TIN you've worked on in the past please?

[neilyj666]

This is an Autodesk University link The Handy Man’s Guide to Dynamic Differential TIN Surface (DDTS) | Autodesk University

[rl_jackson]

Are you asking if, I have 10cm of file that I know will compact to 7cm of fill then, I would say yes it will do that in the volume calcs.

[neilyj666]

The OP wants a weighted depth by which to drop the finished levels to create a formation model rather than a global depth and is correctly suggesting that by taking the areas and depth of the different construction thicknesses, a weighted global depth reduction can be derived.

This approach is reasonable but the DDT is better although takes a bit more effort to set up