Volume of cut/fill breakdown by EG elevation

[autoMick]

Hi, has anyone come up with an efficient method to breakdown the amount of fill (or cut) in a volume surface based on the existing ground elevation?

Sort of like a stage storage curve, but for cut and fill between and existing and future surface. The project is to dredge both sub-tidal and inter-tidal sediments, and then place these sediments in other areas which are also sub- and inter-tidal. I'm trying to work out the net cut/fill for numerous elevation thresholds corresponding to the low and highs for neap and spring tides.

Thanks

Mick

[wfberry]

Sounds like an interesting question.

However, I have no idea what your situation looks like (I would think that others would have the same thought.)  Are you managing a large area or is it a channel?

Bill

BTW, we are in the middle of a 3 day holiday weekend.

[autoMick]

Hi Bill,

The area is actually quite unique in that it is a large enclosed lagoon, but receives tidal flows through the porous structure of a rock wall which forms one of the sides of the lagoon. Prior to construction of the wall, it was part of the main estuary. The project is dredging up sand from the sides of the lagoon to replenish the beaches along the sides. Tidal levels and water exchange within the lagoon are of critical interest and hence the need to document effects on tidal prism, which is the water volume that comes in an out with each tide. This is affected by changes in the bathymetry and whether those changes are below low tide level, or within the inter-tidal area. With numerous tidal scenarios to consider it would make things much easier if Civil3d could do what I'm after somehow.

Cheers

Mick

[Joe-Bouza]

Hi Mick
Not sure how paletable this sounds.
Paste eg into a blank for as many intervals you have lower accordingly . Stack them in the volume dashboard and report.

Or do one and iteratively lower while the dashboard is open and report each action

[ChrisRS]

without any coast line in Arizona, my experience is nonexistent. Even looking at just high and low tide this gets pretty cumbersome. Looking the cut/fill as the difference between the pre/post water volumes avoids having to create multiple FG boundaries or surfaces at intermediate elevations. I would work with the inner/lagoon area and outer area separately. If I misunderstand this, I may have over simplified.image.png

[autoMick]

Hi Joe/Chris,

Joe - I understand you are suggesting to paste the EG into a number of blank surfaces to create copies but I've lost you after that. I can't change the relative levels of the EG or FG, as the cut/fill sides are sloped. The sides of both the cut and fill are gradings.

Chris - I've draw a couple of sections (I'm ignoring neaps tides, just going with a single tide scenario at the moment) to try and explain. 

To explain myself more... conceptually, I need to get the cut solid between EG and FG and slice up that solid at particularly horizontal levels, then do this again for the fill component. Doing that using 3d solids is possible, with about a million steps, but I would really like to have a Civil3d/dynamic way of doing/reporting this. 

I haven't got much experience with the stage-storage tool, but I can't help thinking there's a solution in that somewhere?

Thanks

Mick

Capture.PNG

[Joe-Bouza]

My mistake Mick I though you wanted to the total earth work. Not sure I understand. Are you wanting incremental c&f betweem tide lines or Original ground?

[ChrisRS · Accepted solution]

@autoMick, thanks for the clarification. I think what I proposed can meet your needs. Stage-storage might help; I will get to that later.

Volume surfaces compute cut and fill volumes between a base surface and comparison surface. Typically that means for every interval of interest we need a base and comparison surface pair. The process can be simplified by the use of simple arithmetic.

Looking at your cross section, the Subtidal cut comparison surface is the dredged surface (DG) but the base surface, EG-ST, is not so clearly defined. EG-ST is the  EG surface with in the dredged area up to the low tide elevation, and a flat area at low tide elevation extending to (or beyond) the DR surface. Create EG-ST; paste in a copy of EG; add a boundary that trims the surface to the area below low tide elevation; and a feature line to create the flat spot. 

The surfaces for the intertidal cut are similar, but the flat spot is on the dredged comparison surface. If there was a supratidal cut, both surfaces for the intertidal cut would have flat spots. 

The situation is the same for the Placed fill volumes.

Creation of these surfaces is not extremely difficult, but it by no means trivial. This is not fully dynamic, so it will be tedious in an iterative design/analysis process. 

image.png

My approach avoids the need for these intermediate surfaces by use of simple arithmetic. In a eureka* moment, I just realized that I have suggested  computing dredge volume by taking the difference between the dredged lagoon volume and the dredged lagoon volume. I did not state this before; If I had realized it, I would have.

At this point in your analysis, you have an existing surface, a grudged area surface and a filled area surface. I suggest treating the areas inside and outside the lagoon separately. If you do not, you will need to establish surface boundaries.

Inside, we have EG-IN, and DG.

It is easy to create in inside finish grade surface

Create FG-IN; paste EG; paste DG.  This is dynamic if DG changes.

It is trivial to create a low tide and high tide reference surfaces:
Create a closed feature line at low tide elevation. This can be any shape as long as it fully encloses the cut area and as much of the lagoon as you care to analyze.

Create LT-IN surface; add the feature line. Done.

Create HT-IN surface; Edit Past LT-IN; Edit Raise (HT elev - LT elev). Done.

You can now compute existing subtidal lagoon volume (A),  and existing high tide lagoon volume (B). Existing Intertidal lagoon volume (C) is (B) - (A). (Just arithmetic.) There may be some value to know in these volumes.

Now we can compute the cut volume by creating a volume surface using base: EG-IN and comp: FG. There is no easy way to segment the computed fill.

Now compute dredged subtidal lagoon volume (G),  and dredged high tide lagoon volume (H). Dredged Intertidal lagoon volume (I) is (G) - (H). (Just arithmetic.) There may be some value to knowing these volumes.    

image.png

So, what about those segmented cut volumes? It is all just arithmetic now:

Subtidal cut (16) =  (G) - (A); Intertidal cut (17) = (I) - (G) and

Supratidal cut (18) = (12) - (16) - (17)  

image.png

 The fill condition is similar. It is illustrated but not discussed.

Warning:  This is a situationimage.png where we know that either cut or fill is appropriate, but not both.  At right, the subtidal fill is computed as the fill given by a volume surface with base: EG-IN and comp: LT-IN. A cut area is computed as well, but we ignore that. This is an important shortcut. If our area of interest included both cut and fill, we would need to add boundaries to limit the volume surface to the area of interest. This shortcut is why we need to analyze the lagoon ad placement areas separately. 

Thing a little further:

• You are not limited to just Low Tide and High Tide reference surfaces. It would be trivially easy to make a series of reference surfaces at an interval of your choice. (one at a time)
• As @Joe-Bouza suggests, you can stack these a series of volume surfaces in the volume dash board and report them out.
  ref:comp - EG:R1, EG:R2, EG:R3, EG:R4, FG:R1, FG:R2, FG:R3, FG:R4
  You will still need arithmetic for interval volumes and difference to indicate cut/fill volumes.
  (The Volume Dashboard is dynamic, but anything it reports out is static.)

Now, about stage-storage: 

• Stage-Storage only works with one surface at a time. You would have need two S-S tables. EG lagoon volume and DR lagoon volume. These tables are standard AutoCAD tables the static contents within are available to fields. You would need a third table to calculate (subtract) cut or fill volumes. You could export to excel.
• Stage-Storage only uses contours. If your EG surface is irregular, with pits and peaks, the contour area is unpredictable. Once you get higher, this problem goes away.
• Stage-Storage only uses contour area. It averages or uses a conic approximation. In irregular areas the surface volume calculation is more accurate. For a given slice, if the irregular area is small compared to the flat "sliced" area, the computed volume difference may be negligible.
• Stage-Storage may be a little easier to set up than the Reference Surface-Volume Dashboard approach. (Anyone else have an opinion?)
• Reference Surface-Volume Dashboard approach  may be more flexible that Stage-Storage. Volume Dashboard is dynamic.

That's all I got. Good luck. It would be nice if you update us on how you proceed.

P.S. Here is a slightly updated version of the original picture. (Included for completeness.) 

image.png

[autoMick]

@ChrisRS that is one formidable post there Chris! It's going to take me some time to digest that properly, so if I lay low for a day or so it's not because I don't appreciate the effort!

Regarding your eureka moment - yes when I read your first post that thought came to me as well, so I'd sort of assumed you were thinking that. Which you probably were, but just hadn't realised it yet. It got me thinking there might be an easier way... 

If I just created a good finished ground (FG) surface, then some flat plane surfaces at various tide levels (say Tide1, Tide2, etc.), I could then could just get lagoon water volume surfaces of EG vs Tide 1, EG vs Tide 2 and just mathematically subtract the FG vs Tide 1, FG vs Tide 2 volumes, this should then just give me the change in tidal volume (i.e. cut or fill of bank) between the appropriate levels? I think.

I'll have to test and report back (in a day or so)

thanks

Mick

[autoMick · Accepted solution]

@ChrisRS, I eventually managed to get through this. The solution to my particular problem ended up being solved relatively easily solved by using the volume of water under the various cut/fill scenarios rather than the actual volume of cut/fill of sediment (i.e. your eureka comment). The water volume was manipulated using a flat plane and varying the elevation of that plane for my various tidal thresholds (so basically replicating the real life scenario). Still a bit of spreadsheet work but relatively workable. Not dynamic but simple enough to replicate as needed.

I also went through your extended method and am pretty sure it works, but I got lost in it mainly due to my short attention span. 

Although I would dearly love a reporting tool in Civil3d that can slide up a volume based on absolute elevations, it strikes me that using the 'water volume' method will work, even if there's no actual water involved (i.e. just pretend there is) - so this will be my workaround.

Thanks again for everyone's responses

Mick