Site Imbalance

I'm an owner/builder who bought Kubla Cubed to help with determining the site imbalance of my home build.  I was hoping I could use it to minimize the back and forth with the site plan engineer and my excavator.  The issue I'm having is that the Net volume I'm getting with Kubla Cubed is significantly different then what my excavator is coming up with in his calculation.  I tend to believe him since he has been doing it for 25+ years and he was spot on for another project he did for me.

I've attached the kubla file for this project.  I'm trying to eliminate the porches and garage from the fill imbalance since I will need to fill with gravel to avoid compaction of any soil in those areas.  So I'm really only looking at the cut of the basement and the grading as my points for determining the imbalance.

He is coming up with around 1000 cu yds of fill.  I'm coming up with about 200 cu yds of extra fill.    Interestingly enough if I move the features in the proposed grading down to the bottom, then I show a 1,000 cu yd fill imbalance.

Any ideas as to what I'm doing wrong?

Thanks,
Mike

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I'm having some difficulty attaching the Kubla Project file.

Like for KSP file: https://drive.google.com/open?id=1_cgBjX...SnzXInNj9W

Hi Mike,
Having had a looked at your file, may I suggest that you create a new tab called features and move it between existing and proposed. Then copy 'features' in proposed (ctrl+C) and paste (ctrl+V) into the new tab 'Features' then delete features from Proposed.
What you are then doing is preparing the whole site to it's required level, then digging down for your building works.
This will give the imported fill quantity balance of 1016yd3 as your ground worker calculated.
Hopefully this helps.
Cheers
Tim

I'm an owner/builder who bought Kubla Cubed to help with determining the site imbalance of my home build.  I was hoping I could use it to minimize the back and forth with the site plan engineer and my excavator.  The issue I'm having is that the Net volume I'm getting with Kubla Cubed is significantly different then what my excavator is coming up with in his calculation.  I tend to believe him since he has been doing it for 25+ years and he was spot on for another project he did for me.

I've attached the kubla file for this project.  I'm trying to eliminate the porches and garage from the fill imbalance since I will need to fill with gravel to avoid compaction of any soil in those areas.  So I'm really only looking at the cut of the basement and the grading as my points for determining the imbalance.

He is coming up with around 1000 cu yds of fill.  I'm coming up with about 200 cu yds of extra fill.    Interestingly enough if I move the features in the proposed grading down to the bottom, then I show a 1,000 cu yd fill imbalance.

Any ideas as to what I'm doing wrong?

Thanks,
Mike

---

I'm having some difficulty attaching the Kubla Project file.

Like for KSP file: https://drive.google.com/open?id=1_cgBjX...SnzXInNj9W

Hi Mike 

Welcome to the forums.  I think Tim is correct.  Looking at your project I can't see where a 800 cubic yards of discrepancy could appear unless your excavator is calculating to grade not including the basement and you are calculating to the basement level.  Moving the Feature Surface down in the calculation order in the same phase means it effectively overwrites the platforms so it will be doing what Tim suggested.  You can watch this video for more info on this.



However before being sure that this is the case there are some improvements that could be made to your project so I would recommend doing that first so we can get the full picture. The project is good with a good distribution of contours and points to define terrain.  However there are a couple of issues :

A) The side of the roads should have been defined with break lines to get a crisper edge. (I can show you how to do this).  Also there seems to be no consideration for surface material thickness (subgrade adjustment).  For instance the proposed driveway is gravel, what is the thickness of this gravel ?  On the plan the FF (finished floor) is marked.  This will be the the elevation of the top of the gravel, however an earthworks contractor will not be excavating to that level, they will need to excavate so when the gravel etc... is added it reaches the FFL.

The same is true of the garage and basement but I notice the levels of the platforms do not match the FF on these items.  Is this because you have already adjusted these ?  If so it is easier to put the construction thickness as an offset just to make it clear.  I recommend this video :



The porches and garage we will need to do in a special way.  Is it that you want these only to report cut, not fill.  We can do this, let me know if this is what you want.

Just to confirm, your results are Cut : 983.61yd³ Fill : 791.96yd³ Net : -191.65yd³ (cut)

Is your excavator getting 1000yd³ and a similar cut so near balance ? In which case there's only 208yd³ difference between your results, or is he getting 1000yd³ fill requirement Net : -1000yd³ (cut) I couldn't quite work it out from your original post.

Let me know and I will give you a call and I'm sure we can get to the bottom of it.  Also it is worth considering he may have been taking account of compaction\swell factor, but we will make sure the project is perfect first and then go from there.

Thank you both for responding and I'm seeing that there is a lot to improve in the model.

My excavator is saying that I need approximately 1,000 cu yd of fill to get to the final grading.  I attempted to eliminate the garage and porches from the calculation by setting those areas to the grade since I will need to fill with gravel and I'm just trying to figure out what the backfill and grading imbalance is going to be.    I had modeled a feature (new grading around house), and 4 platforms (basement, 2 porches, and garage).  With this model, which I provided via the link, I came up with approximately -200 cu yds. 

I'll watch the video and attempt to rework the model.  I'm just not understanding how the creation of the features and platforms are interacting with each other to get the final imbalance.

Mike

Thank you both for responding and I'm seeing that there is a lot to improve in the model.

My excavator is saying that I need approximately 1,000 cu yd of fill to get to the final grading.  I attempted to eliminate the garage and porches from the calculation by setting those areas to the grade since I will need to fill with gravel and I'm just trying to figure out what the backfill and grading imbalance is going to be.    I had modeled a feature (new grading around house), and 4 platforms (basement, 2 porches, and garage).  With this model, which I provided via the link, I came up with approximately -200 cu yds. 

I'll watch the video and attempt to rework the model.  I'm just not understanding how the creation of the features and platforms are interacting with each other to get the final imbalance.

Mike

Hi Mike,

Maybe this will be too much information, but there's a couple of points about outlines that are worth mentioning.  Especially the first one could affect the volumes quite a lot:

1. When you define the outline around the proposed (your 'features' surface) this outline should be around the limits of the disturbed area.  To me it looks as though the areas I've highlighted in green are not being disturbed, as the proposed contours have already ended where they meet the existing ground.  Since the software will invent levels in this area and calculate volumes based on these levels, this could affect your volumes quite a bit.
   
2. If I'm understanding you right, you don't want any calculation of the garages, patio and porch because you are calculating this separately as gravel volumes.  You've cancelled them out roughly, by adding platforms in these areas at the existing ground level.  A better way to do this is to add internal boundaries to the feature surface.  If you add an outline inside your main outline it will remove that area from the surface, like a hole in the surface.  You can see I've done this on the attached file, so it shows gray as there's no cut or fill.
   

BTW Tim ->  A very minor point but there's also Ctrl+X to 'cut' an item.  You can then paste with Ctrl+V and it just means you don't have to delete the old surface.  Not a big deal, but might save you some time if you're doing this a lot.

Hope this helps!

Leo

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Hi All

I've had a bit more time to look at this one and from what you are saying mike you are actually out by approx 1200 yd³.  As your excavator is saying you need 1000yd³ to be brought onto the site and your analysis is saying you will actually end up with 200yd³ to get rid of (cart-away it is often called).

I have been going over the site plan trying to account for this discrepancy but can't fully.  I redefined the road using break-lines, and made adjustments to the outline like Leo suggested.  I also separated all the items out into separate phases as Tim suggested so we could analyse them separately.    This is what I got :

Landscape area around the property :
Cut : 219.79 yd³ Fill 810.14 yd³  Net : 590.35 (fill) yd³

House dig to marked basement FFL level : 
Cut : 516.66 yd³ Fill 0 yd³  Net : -516.66 (cut) yd³

Garage to marked FFL.
Cut : 8.20 yd³ Fill 16.26 yd³  Net : 8.06 (fill) yd³

Porch and Patio to marked first floor FFL.
Cut : 0 yd³ Fill 91.18 yd³  Net : 91.18 (fill) yd³

TOTALS FOR WHOLE PROJECT

Cut : 744.62 yd³ Fill 917.58 yd³  Net : 172.96 (fill) yd³

Obviously material thickness\sub grade need to be taken into account.  Over the road that will reduce the fill, over the basement that will increase the cut, however I can't see it making up to the large difference between you and the excavator.  Let me know the surface material thickness and I will add them in.

Let us know the updates on the project, it is always interesting to us to compare the digital modelling with real world results.  There are a lot of other factors relating to site and soil conditions that your excavator might be taking into account that we are not here in a mathematical computer model.  

One thing I might suggest is to send him a download of Kubla Cubed Lite (it is free to use).  This can be used to open Kubla Cubed Professional files, although he will not be able to edit the Professional elements he can view them. Over the phone you can then talk him through how you have broken it down, he might have some input on where your methods differ and you can revise the model or he might revise his estimate seeing the 3D model.  Kubla Cubed uses the Prism Volume method using two Triangulations, this is considered to be the most mathematically complete model.

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  Site Balance Breakdown.kcp (Size: 1.16 MB / Downloads: 1)